Symposium Organizers
John Harding University of Sheffield
Sheng Lin-Gibson National Institute of Standards and Technology
John Spencer Evans New York University
Kiyotaka Shiba Japanese Foundation for Cancer Research
NN1: Bone and Teeth
Session Chairs
Monday PM, November 29, 2010
Liberty B/C (Sheraton)
2:30 PM - **NN1.1
The Nucleation and Crystal Growth Events in the Biomineralization of Calcium Phosphates.
George Nancollas 1 , Baoquan Xie 1 , Elizabeth Cappadonia 1 , Zachary Henneman 1
1 Chemistry, SUNY at Buffalo, Buffalo, New York, United States
Show AbstractAlthough many studies of calcium phosphate crystallization have been made, most have focused only on the final structures and morphologies and have not emphasized the need to consider the molecular contacts between mineral and matrix that drive nucleation, nor the thermodynamic and kinetic controls imposed by matrix and soluble proteins during the nucleation stage. Our work focuses on the earliest events of homo/hetero-geneous nucleation from an initial supersaturated solution phase to the subsequent growth of nuclei. A combination of macroscopic constant composition (CC) and conductimetry has provided new insights into the physical mechanisms of crystal growth and phase stability, and the influences of proteins, peptides and other small molecules. CC mineralization experiments were made at pH 7.40 and 37.0°C, in the presence and absence of polypeptides and amino acids, at a relative supersaturation with respect to hydroxyapatite (σHAP) of 20.9. During the induction period, small increases in the solution pH and conductivity were observed; these events preceded the sharp decrease in solution pH and specific conductance during crystal growth. Microscopic (SEM, TEM) analysis of samples removed at the induction time confirmed the formation of nano-particles. As the reaction progressed, these particles aggregated to larger amorphous calcium phosphate (Ca-P) spheres. The data are consistent with the formation of Posner’s Clusters, Ca3(PO4)2. CC data indicate that polypeptides promoted Ca-P nucleation in a concentration dependent manner. In the presence of Amelogenin the induction time for Ca-P nucleation (σHAP = 18.5) was markedly reduced from 820±55 min (n=3) for control experiments to 600±45 min (n=3) in the presence of 2.0 μmol L-1 rP12, and 535±45 min (n=3) with rP25, respectively. At an equivalent molar concentration, the rP25 C-terminal polypeptide segment promoted Ca-P nucleation to a greater degree than rP12. At 2.0 μmol L-1, the hydrophobic rP148 segment promoted Ca-P nucleation to a greater degree than the full length rP172, 240±50 min (n=3) versus 375±45 min (n=3), respectively. The TEM and SEM data confirmed the formation of monodisperse amorphous Ca-P nano-particles (ca. 50nm) during the induction period. Investigations were made of Ca-P nucleation in the presence of aspartic acid (σHAP= 19.5). At low aspartic acid concentrations (<1.50x10-4 mol L-1), a window of concentration dependent inhibition of nucleation was discovered, in which aspartic acid prolonged the induction time by approximately 350 minutes. At aspartic acid concentrations outside this window, nucleation was promoted. The relative size of the inhibition window was dependent on the value of the supersaturation, σHAP, used for the experiments. Work supported by National Institute of Health, NIDCR (grant # DE003223).
3:00 PM - NN1.2
The Structure of Amorphous Calcium Phosphate (ACP).
Gavin Mountjoy 1 , Kate Wetherall 1 , Chris Storey 1
1 School of Physical Sciences, University of Kent, Canterbury, Kent, United Kingdom
Show AbstractBiomineralisation processes are extremely important for living organisms, and are studied for the insights they provide into synthesis routes for controlled crystallisation. Calcium phosphates are one of the major biomineral families, and are of crucial importance in humans. Reviews of calcium phosphates [1] have clearly established amorphous calcium phosphate (ACP) as a distinct, recognisable, non-crystalline phase, and ACP may be a key intermediate in the skeletal calcification process [2]. Early X-ray diffraction work on ACP lead to the "Posner cluster" hypothesis for the structure of ACP [3], inspired by the hydroxyapatite structure. However, in the following decades the structure of ACP has not been extensively studied. Currently a study of ACP is being carried out using a suite of advanced structural characterisation techniques which are commonly used to study glasses. In order that large and reproducible samples were available, these techniques have been applied to laboratory synthesised samples of ACP [4]. The techniques used include high resolution electron microscopy, neutron and X-ray diffraction, X-ray absorption spectroscopy, NMR spectroscopy, and computer modelling. Preliminary results from this study of ACP will be presented, and will be discussed in relation to the "Posner cluster" hypothesis and to existing models for phosphate glasses. [1] B. Wopenka and J.D. Pasteris (2005) Mat. Sci. Eng. C 25 131.[2] E.D. Eanes (2001) Monogr. Oral Sci. 18 130.[3] F. Betts and A.S. Posner (1974) Mat. Res. Bull. 9 353.[4] F. Abbona, A. Baronnet (1996) J. Cryst. Growth 165 98.
3:15 PM - NN1.3
Hydroxyapatite Nano and Microparticles: Correlation between Control of Morphology and Crystallization Process.
Gill Sang Han 1 , Hyun Suk Jung 1
1 , Kookmin university, Seoul Korea (the Republic of)
Show AbstractAs a versatile biomaterials, hydroxyapatite (Ca10(PO4)6(OH)2, HAp) has attracted increasing interests owing to its chemical and structural similarity to bone and teeth of human body. Also, HAp has been utilized in various applications including reinforcement materials for bioceramics, fillers for bone defects, heavy metal ion exchanger, adsorbing materials for biopolymers, and deodorizing materials. Therefore, controlling the size and morphology of HAp nanoparticles (NPs) is very crucial to make HAp NPs suitable for each application. In current study, we report that HAp NPs with various shapes including ultra-long fibers, platelets, rods, and spheres, can be synthesized by controlling pH of solution which contains calcium nitrate, sodium dihydrogen phosphate dehydrate, urea and gelatin. The phase evolution behavior and morphological change of HAp NPs was monitored as a function of reaction time by using various characterization tools such as X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), Fourier transformed infrared spectroscopy (FTIR). The each HAp possessing various shapes was found to crystallize from different calcium phosphates such as Octacalcium phosphate (OCP), hydroxyapatite (HAp), and amorphous calcium phosphate (ACP), which were initially formed by varying the reaction pH. These results demonstrates that the reaction pH is able to make change in HAp crystallization routes, thereby consequently determining the morphology of HAp NPs. In our study, we also discussed the role of urea and gelatin in controlling the morphology of HAp NPs.
3:30 PM - NN1.4
Ion-Specific Interactions in Aqueous Solution.
Matan Dishon 1 2 , Ohad Zohar 1 2 , Uri Sivan 1 2
1 Physics, Technion - Israel Institute of Technology, Haifa Israel, 2 Russell Berrie Nanotechnology Institute (RBNI), Technion – Israel Institute of Technology, Haifa Israel
Show AbstractEver since the seminal work of Franz Hofmeister in 1888 on the effect of background salt type on the precipitation of proteins in aqueous solution, fair amount of theoretical efforts have been invested in the understanding of such strong ion-specific effects. However, in the absence of dedicated experiments, the explanation of these dramatic effects remained undecided and invariably neglected in ample studies. Motivated by the lack of systematic experimental studies of such a fundamental phenomenon we have launched a series of experiments focused on characterizing differences in the interaction between two negatively charged silica surfaces, as measured by AFM[1]. The study included different monovalent electrolyte solutions: NaCl, KCl, and CsCl in a broad range of ionic concentrations, from 0.1mM to 5M. Force vs. Separation curves reveal that the surface charge of silica is regulated by cation adsorption in addition to silanol deprotonation. Cation adsorption grows monotonically with bare cation radius. As ion concentration is increased surface charge is gradually neutralized by specific cation adsorption, hence, suppressing the repulsion due to electrostatic double layer overlap and revealing van der Waals attraction at a concentration specific for each salt. At pH5.5 the largest ion, Cs+, neutralizes the surface at ~0.1 M, K+ at 0.2-0.5 M and Na+ at >0.5 M. At higher salt concentrations, repulsion reemerges due to surface charge reversal by excess adsorbed cations. When attraction dominates, the force curves are practically identical for the three salts, independent of their concentration. The importance of understanding ion-specific effects of these 1:1 salts lies in the fact that living organisms maintain characteristic electrolyte compositions in their different biofluids. For example, the intracellular fluid of mammalian cells is characterized by high level of potassium (~160mM) and low level of sodium (~10mM), while extracellular environments consist of high sodium (~140mM) and low potassium (~4mM) levels. We have found that in ~150 mM NaCl two negatively charged silica surfaces repel each other but at the same concentration of KCl they will attract. The same charged objects may, hence, repel each other in extracellular ionic environment and attract each other in cell like electrolyte composition.[1] M. Dishon, O. Zohar, U. Sivan, Langmuir 25 (5), 2831 (2009)
4:15 PM - **NN1.5
Acidic Domains in DMP1 Functions in the Formation of Calcified Tissues of Bone and Dentin.
Ann George 1
1 , University of Illinois at Chicago, Chicago, Illinois, United States
Show AbstractThe collagenous matrices of bone and dentin are mineralized by precise cell-mediated mechanisms. They have superior mechanical properties due to their complex architecture. Control over biomineral properties can be accomplished by regulation of particle size, shape, crystal orientation and polymorphic structure. It is now well established that unique proteins are present in the extracellular matrix and that their interaction with the collagen matrix control the placement, nucleation, orientation and growth of the mineral crystals. These organic macromolecules can also stabilize an amorphous precursor phase, which plays an important role in biomineralization. Dentin matrix protein 1 (DMP1) is an acidic noncollagenous protein synthesized by the osteoblasts and odontoblasts and localized specifically in the mineralized matrix of bone and dentin. It is now known that DMP1 is a pleiotropic noncollagenous protein which mediates a variety of biological functions including terminal differentiation of osteoblasts and odontoblasts and in the mineralization of the extracellular matrix. Terminal differentiation of these cells is a complex process requiring the integration of numerous signaling and transcriptional networks. The central hypothesis of the proposed studies is that DMP1 plays an important and unique role during maturation of odontoblasts, leading to the formation of mineralized dentin. DMP1 was shown to nucleate and lead to hierarchical assembly of hydroxyapatite in vitro. A high content of aspartic acid and glutamic amino acid residue content is considered to be an important requirement for matrix proteins to nucleate hydroxyapatite. 45Ca-binding assay results demonstrate that DMP1 has high calcium binding capacity, when compared to BSA, which was reported to be a weak calcium binding protein. Results from this study demonstrate that DMP1 binds calcium ions and initiates the formation of a transient amorphous calcium phosphate precursor phase. Subsequent nanocrystals that emerged from this phase were found to expand and aggregate into microscale, plate-shaped hydroxyapatite crystals, with preferred orientation in their c-axis. The Ca/P ratio of the de-novo crystals was determined by Energy Dispersion X-ray to be 1.67±0.02, which was consistent with the chemical formula for hydroxyapatite as Ca10(PO4)6(OH)2. Identification and characterization of functional domains in DMP1 demonstrate that inter-molecular assembly of acidic clusters in DMP1 is essential for the formation of a beta-sheet template for mineral nucleation. Circular dichroism studies of 2 acidic peptides identified in DMP1 demonstrate the formation of intermolecular sheet structures. This protein template induced by calcium could be the structural basis for self-assembly. Results demonstrate that specific acidic clusters in DMP1 provide the molecular design necessary for controlling the formation of c-axis oriented calcium phosphate crystals. Supported by NIH grant: DE 11657
4:45 PM - NN1.6
Biomimetic Growth of Hydroxyapatite at the Surface of Titanium Implants: All Steps Studied by SEM and Cross-sectional TEM.
Egle Conforto 2 , Daniel Caillard 1 , Lenka Muller 3 , Frank Muller 3
2 , Universite de La Rochelle, La Rochelle France, 1 CEMES, CNRS, Toulouse France, 3 , University of Erlangen-Nurnberg, Erlangen Germany
Show AbstractThe chemical affinity between the bone and the implant surface is often searched in the aim of improving osteointegration. Bone is a natural composite material consisting of collagen, hydroxy carbonated apatite (HCA) and water, where the crystallographic c-axes of the plate-shaped apatite crystals are well aligned with the long axes of the collagen fibrils. Thermal plasma spray is often used to recover the implant surface with an apatite layer but this technique cannot guarantee the layer adherence at the interfaces. The biomimetic growth of HCA to the implant surface has as goal to increase the bone-implant chemical affinity and to minimise the risks of surface layer delaminating [1]. The sequence of steps of a chemical treatment having as goal to induce the nucleation and the growth of HCA at the surface of titanium implants was studied by scanning electron microscopy, and for the first time as a function of depth by transmission electron microscopy in cross-section [2, 3]. After an acid etching as the first step, a rough titanium hydride layer is observed on the surface of a titanium substrate, which remains unchanged after subsequent treatments. This layer has surprisingly good mechanical and adhesion properties onto the titanium substrate [2]. In the second step, soaking in NaOH solution induces the growth of nanobelt tangles of nanocrystallized, monoclinic sodium titanate at the surface of the hydride layer, with average composition Na2Ti6O13. After soaking in simulated body fluid (SBF), which is the third step, sodium titanate transforms into calcium titanate by ion-exchange in the monoclinic nanobelt structure, keeping same crystalline parameters. HCA, of a hexagonal structure, then grows and embodies the tangled structure showing a preferential direction growth along its “c”-axis, perpendicular to the substrate surface. This growth behaviour is very similar to that found in the mineral part of mammalian bone, where the c-axes of plate-shaped apatite crystals are well aligned with the long axes of the collagen fibrils. In spite of its low probability of nucleation per unit surface, HCA can grow on Ca-rich titanate because the nanobelt structure offers a very large free surface in contact with the SBF. Although there is no deep interpenetration of HCA and titanate, the anchoring is strong enough to prevent interfacial decohesion.References[1] H.M. Kim, F. Miyaji, T. Kokubo, T. Nakamura, J. Biomed. Mater. Res. 32 (1996) 409.[2] F.A. Müller, L. Müller, D. Caillard, E. Conforto, J. Crystal Growth 304 (2007) 464.[3] E. Conforto, D. Caillard, L. Müller, F.A. Müller, Acta Biomaterialia 4 (2008) 1934.[4] E. Conforto, D. Caillard, B. O. Aronsson, P. Descouts, Phil. Mag. 84 (2004) 631.
5:00 PM - NN1.7
Kinetic Studies of the Demineralization and Deproteination of Bone.
Ana Castro 1 , Ekaterina Novitskaya 2 , Po-Yu Chen 2 , M. del Pilar Sanchez 5 , Gustavo Hirata 3 , Joanna McKittrick 2 4
1 Fisica de materiales, CICESE, Ensenada, Baja California, Mexico, 2 Materials Science and Engineering Program, UC San Diego, La Jolla, San Diego, California, United States, 5 Acuicultura, CICESE, Ensenada, Ensenada, Mexico, 3 Biomateriales, CNyN-UNAM, Ensenada, Baja California, Mexico, 4 Mechanical and Aerospace Engineering, UC San Diego, La Jolla, San Diego, California, United States
Show AbstractThere is an increasing interest on the study of bone demineralization due to the clinical applications of demineralized bones as scaffolds for bone repair and for tissue engineering. On the other hand, research on bone deproteination allows a better understanding of the structural, chemical and synergistic interactions between the mineral and protein phases on bone. In the present work, cortical and cancellous bovine femur bones were demineralized and deproteinated. Demineralization was performed at different temperatures and concentrations of hydrochloric acid. Deproteination was carried out using 6% NaOCl at distinct temperatures. The goal of this work was to calculate the kinetic parameters of the demineralization and deproteination reactions. Demineralization and deproteination were found to follow first-order kinetics. The rate of demineralization increased with both HCl concentration and temperature. Three different stages were clearly identified during the demineralization reactions: a) in the first stage, the rate constant increased as HCl diffused from the periphery to the core of the sample; b) in the second stage, demineralization occurred at steady state, and finally, c) in the third stage, the rate constant diminished. The activation energy for demineralization increased with increasing HCl concentration. Concerning on deproteination, calculations for activation energy are presented based on the rate constant values obtained at different temperatures. This work provides a better understanding of the details of bone demineralization and deproteination reactions.
5:15 PM - NN1.8
Mechanical and Physical Properties of Demineralized Bone.
Ekaterina Evdokimenko 1 , Ana Castro-Cesena 2 , Po-Yu Chen 1 , Joshua Vasquez 1 , Robert Urbaniak 1 , Steve Lee 1 , Joanna McKittrick 1
1 Materials Science and Engineering, UCSD, La Jolla, California, United States, 2 , Centro de Investigación Científica y de Educación Superior de Ensenada, Ensenada Mexico
Show AbstractBone is a hierarchically structured composite material consisting of a biopolymer (type-I collagen) and a mineral phase (carbonated hydroxyapatite). Bone loss (osteoporosis) and demineralization occur as bones aged and are a major cause of bone fractures. The mineral/collagen interaction is important in understanding how this affects the bone fracture. Investigation of the microstructural and mechanical properties of bovine femur bone was carried out on partially demineralized, completely deproteinated, and untreated bone samples.Bone samples were demineralized at different degrees through a controlled process by aging in 0.6N hydrochloric acid (HCl). Demineralization process was quantitatively analyzed by the inductively coupled plasma optical emission spectrometry (ICP-OES). Demineralization reaction was found to be the first order reaction. Bone samples were completely deproteinated by aging in 6 wt.% sodium hypochlorite (NaOCl) solution at 37°C. Structural features of partially demineralized, completely deproteinated, and untreated bone samples were studied by optical microscopy (OM) and scanning electron microscopy (SEM). At the microscale, SEM images showed that the minerals are aligned in a coherent manner, forming a continuous network. The chemical composition changed at different stages of demineralization, its relation to mechanical properties was also examined. Mechanical properties of partially demineralized bone were analyzed on the steady state region, where samples were demineralized uniformly (35 vol.%, 45 vol.% and 55 vol.%). Compression behavior of partially demineralized, completely deproteinated and untreated bone samples were investigated in all three anatomical directions. The radial direction appears to be the strongest and the stiffest bone direction. Moreover, compression tests showed that the sum of the stress-strain curves for completely demineralized and completely deproteinated bone was far lower than that of the untreated bone, indicating a strong molecular interaction between a collagen matrix and a mineral phase. This research is supported by the National Science Foundation grant DMR 0510138 and UC-MEXUS grant.
5:30 PM - NN1.9
Refined Control of Three Dimensional Biomineralization of Hydrogel with Matrix Properties.
Chaenyung Cha 1 , Hyunjoon Kong 2
1 Chemistry, University of Illinois, Urbana, Illinois, United States, 2 Chemical and Biomolecular Engineering, University of Illinois, Urbana, Illinois, United States
Show AbstractExtensive efforts have been made to understand the role of an extracellular matrix in regulating biomineralization in order to ultimately harness the beneficial role of minerals in regulating cellular activities in a three-dimensional (3D) matrix. We hypothesize that density of chemical motifs binding with mineral ions and water diffusivity through a 3D matrix should be controlled in an integrated manner to derive a mineralized matrix advantageous to supporting viability of encapsulated cells. This hypothesis is examined using a hydrogel consisting of poly(ethylene glycol) (PEG), poly(propylene glycol) (PPG), and methacrylic alginate (MA) as a model system, because it allows us to independently control the matrix properties with mass fractions of three polymers of the hydrogel as well as its pore size with lyophilization process. Water diffusivity was controlled with varying the ratio of PEG and PPG to control the hydrophobicity, and charge density was controlled with negatively charged MA. At a high charge density controlled by mass fraction of MA, decreasing water diffusivity of the microporous hydrogel with increasing PPG (hence decreasing PEG) promotes the growth of apatite layers. In contrast, decreasing water diffusivity in nanoporous hydrogel resulted in the formation of calcium carbonate minerals. At lower charge density, the mineral formation was significantly reduced. The extent of mineralization in nanoporous hydrogel was significantly less as compared to microporous hydrogel. The relationship between the hydrogel variables and the degree and type of mineralization is related to the change in supersaturation of mineral ions. The microporous hydrogel which presented the lower water diffusivity and subsequently promoted apatite formation significantly enhances viability of cells incorporated into the mineralized micropores. Overall, the results of this study will be highly useful to better understand the 3D biomineralization process, and further provide a novel strategy of creating a mineralized matrix potentially used in cell therapies and tissue engineering.
Symposium Organizers
John Harding University of Sheffield
Sheng Lin-Gibson National Institute of Standards and Technology
John Spencer Evans New York University
Kiyotaka Shiba Japanese Foundation for Cancer Research
NN2: Assembly I
Session Chairs
Tuesday AM, November 30, 2010
Liberty B/C (Sheraton)
9:30 AM - **NN2.1
Genetic Engineering With Solid-Binding Peptides Broadens the Fields of Biological And Biomimetic Materials Synthesis And Assembly.
Candan Tamerler 1 2 , Mehmet Sarikaya 1
1 Materials Science & Engineering AND GEMSEC, University of Washington, Seattle, Washington, United States, 2 Molecular Biology & Genetics, Istanbul Technical University, Istanbul Turkey
Show AbstractBiological or biomimetic synthesis of nanoinorganics have been a major focus in hard tissue engineering as well as developing a new generation of hybrid materials through environmentally-benign processing. Bio-based molecular building blocks are, therefore, developed for practical water-based pathways to high performance multifunctional engineered materials, molecular self-assembly-based fabrication processes and novel biologically compatible structures. In our approach, we use evolutionary engineering principles to biocombinatorially select, bioinformatically design, and genetically synthesize peptides and multifunctional proteins as molecular tools towards realizing genetically engineered molecular materials. Following the fundamental principles of genetic design, molecular recognition, and biological self-assembly, we can now use recombinant DNA technologies and biochemical conjugation to produce single or multifunctional peptides and fusion proteins that can bind to any solid material (metal, ceramic, semiconductor, mineral) system. Here we provide examples in the use of GEPI, genetically engineered peptides for inorganic materials, as molecular linkers to conjugate nanosystems, probes for targeting and growth modifiers in the processing of materials for designed functions. These peptides are used, e.g., in synthesis processes as catalyzers for controlled formation of nanoscale-inorganic solids and hybrid scaffolds in tissue restoration and regeneration; probes for targeted labeling of cells and tissues; surface linkers for directed enzyme immobilization, and molecular coaters in thin biofilm formation. The presentation will provide an overview of the multidisciplinary approaches on how functional materials can now be biologically generated, starting from the tailored molecules and up to cm-dimensions, hierarchically, using genetically engineered biological building blocks. Research supported by NSF, through GEMSEC, an MRSEC at UW, NSF-BIOMAT and TUBITAK-NSF IRES Joint Projects, and TR-SPO.
10:00 AM - NN2.2
Microtubule Biotemplates for Hybrid Nanostructure Growth.
Erik Spoerke 1 , Bridget Connor 1 , Marlene Bachand 1 , George Bachand 1
1 , Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractMicrotubules (MTs) are dynamically assembled biological filaments ranging in length from a less than a micrometer to more than a millimeter. In their natural cellular environments, these chemically and functionally rich biological nanofibers mediate critical functions ranging from chromosome separation during cell division to the direction of intracellular cargo transport by motor proteins stepping along the lengths of organized MTs. In vitro, we have learned to manipulate the surface chemistry, polymerization, and assembly of these versatile and dynamic MTs with the intention of utilizing them as functional nanoscale templates for biomineralization. In the present work, we describe how controlled polymerization and assembly of MTs can be integrated with biomineralization and biometallization chemistries to create unique hybrid, nanoscale architectures. Not only do these assemblies offer valuable insight into biomediated nanomaterials synthesis, but they provide a biochemical model we may use to expand novel bioinspired strategies for nanomaterials synthesis and assembly to completely synthetic systems. Sandia National Laboratories is a multi program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
10:15 AM - NN2.3
Biomimetic Template Directed Synthesis of One-dimensional Inorganic Nanostructures.
Mustafa Guler 1
1 UNAM-Institute of Materials Science and Nanotechnology, Bilkent University, Ankara Turkey
Show AbstractMineralized biological materials such as shells, skeleton and teeth encompass biomineralization process. Biomimetic materials exploit biomineralization process to form functional organic-inorganic hybrid nanostructures. In this work, we mimicked the biomineralization process by using self-assembled peptidic nanostructures. We designed and synthesized an amyloid-like peptide self-assembling into nanostructures. The nanostructures were functionalized with chemically active groups to enhance affinity for metal ions. The metal chelating groups were used on the peptide scaffold to accumulate inorganic precursors on the self-assembled peptidic nanostructures. The self-assembly process and template effect were characterized by CD, FT-IR, UV-vis, fluorescence, TGA, SEM and TEM. The self-assembled organic nanostructures were used as a template to form various one-dimensional inorganic nanostructures by addition of appropriate precursors. Herein, a new bottom-up approach was demonstrated to form silica, titania, zinc oxide, zink sulfide ans cadmium sulfide nanostructures that can yield wide opportunities for producing high-aspect-ratio inorganic nanostructures with high surface area. The materials developed in this work have vast potential in catalysis, photovoltaics and semiconductor applications.
10:30 AM - NN2.4
Ice-templated Materials: Structures Aligned by Uni-directional Freezing.
Min Kyung Lee 1 , Hye Seung Lee 1 , Sinwoo Kim 1 , Jonghwi Lee 1
1 Department of Chemical Engineering and Materials Science, Chung-Ang University, Seoul Korea (the Republic of)
Show AbstractDirectional freezing is a simple method to produce aligned porous materials in the form of 2D patterns. A solvent-typically water but also organic solvents-is frozen uni-directionally, and the structures of pores after drying reflect the spaces (templates) occupied by the uni-directionally frozen and aligned crystals of solvents. The freezing process can be carried out in a more controlled manner to orientate the growth of ice crystals in one direction. While the solvent is freezing, the growth of ice crystals expels the nanoparticles (or polymer molecules) to grain boundary region (cryo-concentration). Under these conditions, the nanoparticles (or polymer molecules) were aggregated between the growing ice crystals. The size of ice crystals could be adjusted by varying freezing rate and dispersion concentration. Herein, we show that directional freezing is a simple and flexible method applicable to range of materials (metal-oxide nanoparticle dispersions, polymer colloidal dispersions and polymer solutions). In this approach, SiO2 nanoparticles, TiO2 nanoparticles, poly(tetrafluoroethylene) (PTFE), poly(vinylidene fluoride) (PVDF) and cellulose acetate were used to investigate the relationships between structural properties and freezing conditions. We demonstrated that the free-standing films of 20-200 μm thickness and 50-80 vol% through-thickness porosity could be prepared from precise control of freezing rate and direction, and annealing methods. Also, it was discovered that PVDF crystallized into an oriented ferroelectric β phase by uni-directional freezing, which could potentially enhance ferroelectricity and piezoelectricity. Given the simplicity and diversity of this method, we expect potential applications in a wide range of areas.
10:45 AM - NN2.5
General Mechanism for Gel-Incorporation into Single Crystals.
Lara Estroff 1 , Hanying Li 1 , Zhi Seh 1 , Miki Kunitake 1
1 Department of Materials Science and Engineering, Cornell University, Ithaca, New York, United States
Show AbstractThe phenomenon of matrix-incorporation has been identified in both biominerals and gel-grown crystals, spurring investigation into the mechanisms by which organic matrixes can become incorporated inside of inorganic single-crystals. Here, we expand upon our original studies of calcite single-crystals grown in agarose hydrogels to include other gel-crystal pairs including calcium tartrate tetrahydrate (CTT) crystals grown in silica gels and glycine crystals grown in agarose. For both calcite and CTT, by systematically changing the reactant and gel concentrations, we have demonstrated complete incorporation of gel material as well as complete exclusion of the gel material. Gel incorporation is determined via SEM (both systems), TGA (calcite/agarsoe) and WDS (CTT/silica). Based on these results, a general gel-incorporation mechanism is proposed in which there are two important mechanisms: 1) a balance between a disjoining force that pushes the gel material away, and a hydrodynamic force that couples to the resistance of the gel network to pull the gel towards the crystal; 2) a competition for available ions that occurs between growth fronts screened and unscreened by the gel. These results have led to design criteria for polymer-reinforced crystalline materials with unique structure-property relationships. Insights provided by this work may help to elucidate the formation mechanism(s) and properties of biogenic single crystals with incorporated organic material.
11:30 AM - NN2.6
Formation and Transformation of Calcium Phosphate Precursor Phases During Nucleation and Growth of Hydroxyapatite on Collagen.
Jinhui Tao 1 , J. De Yoreo 1
1 Molecular Foundry, Lawrence Berkeley Lab, Berkeley, California, United States
Show AbstractInteractions between mineral constituents and insoluble organic matrices appear to direct formation of biomineral structures. In bone, apatite crystals are arranged with the (100) face in contact with the collagen, which is thus assumed to control the nucleation stage of apatite formation. However, the influence of collagen on the thermodynamics and kinetics of nucleation are poorly understood. Moreover, the mechanism of apatite growth and the role of soluble proteins in modulating growth following nucleation have not been determined. In this investigation, we are using in situ AFM, high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy and molecular dynamics (MD) to address these gaps in our knowledge.Type-I collagen was physically adsorbed as ordered fibers onto mica surfaces using solutions containing K+ at pH 4.00. Nucleation experiments were performed at pH 7.40 and relative supersaturations S = 9 - 30 with respect to hydroxyapatite (HAP). The number density of mineral nuclei on collagen as a function of time t was measured by AFM and the mineral phase was determined by Raman spectroscopy and HRTEM. At the highest values of S, nuclei consisted of amorphous calcium phosphate (ACP), which quickly transformed to octacalcium phosphate (OCP) before slowly changing to HAP. At lower S, OCP formed first, but eventually transformed to HAP. At the lowest values of S, HAP nucleated directly. The AFM data showed a monotonic increase in nuclei number density vs. both S and t. Based on the relationship between nucleation rate and S, the interfacial free energy of HAP on collagen was determined.MD simulations were performed using GROMACS. The segment (Hyp-Pro-Gly)5 was used to model collagen and was initially placed in a box of water (5 nm×5 nm ×5 nm) with 18 calcium and 12 phosphate ions or 2 calcium phosphate clusters (Ca9(PO4)6). Simulations were run at 298 K and 101.3 kPa for 10 ns. The results indicate carbonyl groups have a tendency to serve as nucleation sites due to their strong binding to calcium ions and calcium phosphate clusters.At low S (S < 20), growth of single crystal HAP seeds occurred on atomic steps with a kinetic coefficient per Ca ion similar to that measured for other inorganic salts like calcite. However, the extremely low solubility (< 0.04 micromolar) resulted in a normal growth rate of less than 25 pm/hr at S =10. At higher supersaturation (S > 20), the mechanism switched to 3D nucleation of ellipsoidal particles on the crystal surface that transformed to triangular islands consistent with the facet orientations of the underlying HAP seed. This resulted in a crystal morphology consisting of oriented sub-grains. Gradual dissolution of the original seed revealed a similar morphology suggesting formation by oriented particle aggregation.
11:45 AM - NN2.7
Mesostructured Calcium Phosphate Nanocomposites from Evaporative Co-assembly with Block Copolymers.
Rui-Qi Song 1 , Lara Estroff 1 , Ulrich Wiesner 1
1 , Cornell University, Ithaca, New York, United States
Show AbstractDespite a growing recognition of the widespread occurrence of nanoparticles assemblies in biominerals and their multiple functions in the skeletal design, mechanical protection, nutrition transportation, and creation of dynamic optics, organizing nanoparticles to biomimetic analogous with three dimensional ordered mesostructures has proved to be challenging. We present results from the evaporative co-assembly of block copolymer and silane-functionalized calcium phosphate sol, leading to the lamellar CaP-12 and cross-linked lamellar CaP-17 hybrid mesostructures with controlled spatial manipulation of nanoparticles over several length scale. Preliminary results demonstrate, while oxygen plasma etch of CaP-17 can produce an ordered mesoporous calcium phosphate-silica nanocomposite with continuous structures and large pores (≥ 100 nm), hydrolysis of CaP-12 leads to ordered lamellar hydroxyapatite-silica mesostructures with 100 nm interlayer spacing distance. The resulting calcium phosphate-silica nanocomposites provide promise for the synthesis of specifically designed material for dental repair.
12:00 PM - NN2.8
Improved Mechanical Stability of Dried Collagen Membrane after Metal Infiltration.
Seung-Mo Lee 1 , Eckhard Pippel 1 , Oussama Moutanabbir 1 , Ilja Gunkel 2 , Thomas Thurn-Albrecht 2 , Mato Knez 1
1 , Max Planck Institute of Microstructure Physics, Halle(saale) Germany, 2 , Institut für Physik, , Martin-Luther-Universität Halle-Wittenberg, Halle(Saale) Germany
Show AbstractFew percent of transition metals impregnated inside some biological organisms in nature remarkably improve such organisms’ mechanical stability. While the lure to emulate them for development of new biomimetic structural materials has been great, the practical advances have been rare due to the lack of proper synthetic approaches. Multiple pulsed vapor phase infiltration proved successful for the preparation of such transition metal impregnated materials with highly improved mechanical stability. The artificially infiltrated metals (Al, Ti or Zn) from gas phase lead to around 3 times increase of toughness (in terms of breaking energy) of natural collagen in a dried state. In addition, the infiltrated metals apparently induce considerable crystallographic changes in the natural collagen. This infiltration approach can be used as guide for the synthesis of novel bio-inspired structural materials.
NN3: Assembly II
Session Chairs
Tuesday PM, November 30, 2010
Liberty B/C (Sheraton)
2:30 PM - **NN3.1
Bio Nano Process: A new Nanodevice Fabrication Process by Biomineralization and Protein Self-organization.
Ichiro Yamashita 1 2
1 Materials Science, Nara Institute of Science and Technology, Ikoma Japan, 2 ATRL, Panasonic, Seika, Kyoto Japan
Show AbstractWe proposed Bio Nano Process (BNP)1), which produces nano-devices by biomineralization and protein self-organization. This is one of wet-nanotechnology processes where protein supramolecules with inorganic materials self-organized into functional structures, or key component of nano devices. We have been developing nanodevices which operate based on the excellent properties of nanoparticles (NPs) and nanowires (NWs). Inorganic NPs and NWs were artificially synthesized employing protein supramolecules having inner cavities. NPs are produced by cage-shaped proteins, apoferritin and Dps protein from Listeria innocua, and NWs are produced by tubular proteins Tobacco Mosaic Virus. The inner cavities work as spatially restricted chemical reaction chambers and homogenous NPs and NWs of metal-complex or semiconductor materials were successfully produced. The selective biomineralization in the cavities needs electrostatic potential difference between inside and outside, and it has been getting clearer that the nucleation site has strong connection with charged amino-acids. 2).The obtained protein supramolecules with NP/NW were let self-organize into functional nano-structures on the substrate. The processes are carried out in aqueous solution and ambient temperature. Arrays of several kinds of NPs on silicon surface were produced and used as charge storage nodes of floating gate memory3). Combination of nano-etching and the BNP was also studied and successfully produced quantum wells with precise size control4) and they are now being applied to quantum well solar cells5). Applying the BNP, we are now developing ReRAM, TFT, biosensors, and other nanodevices. 1) Yamashita, Thin Solid Films 2001, 393, 12-16.2) M. Kobayashi, et al., Nano Lett. 2010 10 (3), 773–7763) A. Miura et. al., Jpn. J. Appl.Phys., 2006, 45, L1-L3.4) Chi-Hsien Huang et. al., J. Appl. Phys., 2009, 48, 04C187-1-04C187-65) Chi-Hsien Huang, et. al., J. Appl. Phys., 2010, 49, 04DL16-1-04DL16-5
3:00 PM - NN3.2
Using Biogenic Silica Nanostructures as Template to Fabricate Metal-alloy and Carbon Nano Materials.
Kai-Chun Lin 1 , B. Ramakrishna 1 , Huang-Chiao Huang 2 , Kaushal Rege 2
1 School of Materials, Arizona State University, Tempe, Arizona, United States, 2 Chemical Engineering Department, Arizona State University, Tempe, Arizona, United States
Show AbstractBiogenic silica nanostructures, derived from diatoms, posses highly ordered porous hierarchical structures and provide flexibility in design due to the availability of a great variety of shapes, size, and symmetries from the over 100,000 known species. These silica cell walls have unique nanostructured patterns in the range from 20 nm to 70 nm that can be hexagonal, rod-shaped, or circular depending on the species. These advantages have been exploited for using these cell walls as a template to fabricate nanotubes or nanorods towards the goal of developing chemical and biological sensors and electrical devices. Results from the study of fabrication of nanotubes and nanorods will be presented for depositing noble metals including gold and silver inside nanoporous diatom cell walls using electrochemical means to form metal alloy nanorods. A similar method based on the deposition of gold by vacuum evaporation on the diatom cell walls was employed for the fabrication of gold nanostructures. We also fabricated carbon nanorods by filling the nanopores of cell walls with sucrose and then converted to carbon by treatment with sulfuric acid. The silica cell walls were sacrificed by using sodium hydroxide solution to yield metallic or carbon nanorods. These structures across a wide length scale regime have been characterized by scanning electron microscopy. We expect to leverage the understanding of the fabrication of composite nanorods by metallic or carbon materials towards designing hybrid devices for applications in sensor technologies and electrical devices.
3:15 PM - NN3.3
Syntheses of Metal and Metal Oxide Particles by Genetically-engineered Protein Templates.
Silke Behrens 1 , Arnon Heyman 2 , Sarah Essig 1 , Wilhelm Habicht 1 , Oded Shoseyov 2
1 Institute for Technical Chemistry, Karlsruhe Institute for Technology, Karlsruhe Germany, 2 The Robert H. Smith Institute of Plant Science and Genetics, The Faculty of Agriculture, The Hebrew University, Rehovot Israel
Show AbstractProtein superstructures have been used to synthesize particles and nanowires, providing unique inorganic-biomolecule hybrids with multifunctional properties derived from both the inorganic and the biological material. We report the synthesis of metal nanoparticles and metal oxide particles using genetically modified stable proteins (SP1). SP1 is expressed during drought in aspen plants (populus tremula) and has an extremely high thermal and chemical stability. Material specific hexapeptides were genetically fused to the N-terminus of SP1 thus obtaining variants with peptidic aptamers facing the inner-pore of the protein ring structure. We here demonstrate chemical processes that allow the synthesis of monodisperse Pd nanoparticles and TiO2 particles in the presence of the genetically-engineered SP1 mutants. The resulting hybrids were investigated, e.g. by electron microscopy (TEM/REM), CD spectroscopy. Our studies demonstrate that these stress-related protein mutants are not only appealing templates for synthesizing monodisperse particles, but also the generated particles provide a mortar to construct novel geometrical architectures of hybrid nanoparticle – protein complexes.
3:30 PM - NN3.4
The Structure-based Color of Natural Petals Discriminated by Polymer Replication.
Seung-Mo Lee 1 , Mato Knez 1
1 , Max Planck Institute of Microstructure Physics, Halle(saale) Germany
Show AbstractThe optical appearance of many flowers in nature relies on their inherent pigments (“chemical color”) as well as on the epidermal cells’ surface structure (“structural color”). The later is created by the combination of appropriate amounts of regular and irregular micro/nano sized features. With a biotemplate approach, we have separated the structural coloration from the chemical coloration by reproduction of a red-rose petal’s intricate surface structure in a pigment-free polymer. From UV-vis reflectance measurements we observed that the hierarchical micro/nanostructures on the red-rose petal surface induce a pronounced effect on the reflectivity of the polymer replica. Namely, the optical reflectance was easily modulated and a filtering effect in a specific wavelength range was added. More notably, it is observed that a variation of the size of the micro/nanostructures on the petal surface leads to an effective modification of the reflectance. These results could provide useful tips for biomimetically designed optical devices, emulating natural petal structures.
3:45 PM - NN3.5
One-pot Synthesis of 1.4 nm Au Nanoparticles on Self-Assembled Rosette Nanotubes.
Rahul Chhabra 1 3 , Jesus Moralez 1 3 , Jose Raez 1 3 , Takeshi Yamazaki 2 3 , Jae-Young Cho 3 , Andrew Myles 3 , Andriy Kovalenko 2 3 , Hicham Fenniri 1 3
1 Chemistry, University of Alberta, Edmonton, Alberta, Canada, 3 , National Institute for Nanotechnology, Edmonton, Alberta, Canada, 2 Mechanical Engineering, University of Alberta, Edmonton, Alberta, Canada
Show AbstractA one-pot synthesis of 1.4 nm Au nanoparticles on self-assembled rosette nanotubes (RNTs) is described. These RNTs, which are functionalized on their outer surface with well-organized lysine groups, were self-assembled from a guanine-cytosine DNA base analogue called the G^C base.1 Subsequent incubation of the RNTs with a gold precursor followed by reduction resulted in distinct Au nanoparticles on their outer surface that were nearly monodisperse (~1.4 nm) and organized in a helical fashion.2 Overall, these Au nanoparticle loaded-RNTs offer great potential for applications in nanoelectronics, photonics and catalysis where well-defined organization of nanoparticles is a foremost requirement. This paper will discuss the design, supramolecular organization of this hybrid material, and its mechanism of self-assembly and self-organization. 1. Fenniri, H.; Mathivanan, P.; Vidale, K. L.; Sherman, D. M.; Hallenga, K.; Wood, K. V.; Stowell, J. G. J. Am. Chem. Soc. 2001, 123, 3854.2. Chhabra, R.; Moralez, J. G.; Raez, J.; Yamazaki, T.; Cho, J.-Y.; Myles, A. J.; Kovalenko, A.; Fenniri, H. J. Am. Chem. Soc. 2010, 132, 32.
4:30 PM - **NN3.6
Applications of Peptide-based Mineralization to Lithography, Sensor Chips, and 3D Hybrid Nanoparticle (NP) Superlattices.
Hiroshi Matsui 1 , Yoshiaki Maeda 1
1 Dept. of Chemistry, City University of New York-Hunter College, New York, New York, United States
Show AbstractRecently, we developed novel metal/semiconductor mineralization methodology on the surfaces of the bionanowire arrays or silicon substrates bio-catalytically at room temperature when the mineralizing peptides and enzymes were conjugated on these surfaces, and interestingly the size, the inter-particle distance, and the orientation of NP domains could be controlled by conformation and charge distribution changes of these peptides and enzymes. This type of assembly can also be integrated with lithography to create nanoscale metal/semiconductor patterns, called biomineralization lithography. The ability to control the self-assembly of nanoscale materials into complex three-dimensional (3D) architectures from functional building blocks could allow further development of complex device configurations. DNA bionanotechnology has recently been used to precisely assemble 3D shapes from DNAs in small scale, however peptides are another of nature’s building blocks with even more specificity, robustness, and versatility for assembly that can be exploited to design new 3D architectures. In this part, nanoscale peptides and ligand-functionalized nanoparticle hubs were self-assembled into micron scale 3D cube-shaped crystals, creating a physical framework for the proposed biomimetic assembly strategy. In this approach we took advantage of the naturally robust assembly of collagen triple helix peptides and used them as nanowire building blocks for the 3D crystal generation. Using streptavidin-functionalized Au nanoparticles and the alpha 1 chain of type I wild type collagen specifically modified with a biotin moiety in vivo, we created micro-sized cubes with peptide nanowires as frames and Au NPs as joints. SAXS measurement reveals the position of NPs in peptide cage in these cubes, and the structural change of the peptide-NP unit cell by tethering the size of the NP joints created various shapes of crystals. This simple, rapid fabrication protocol produces high yields of 3D materials in controlled shapes, dependent on the design of the NP junctions, with extremely high yields, promising ease and flexibility in manufacturing future functional devices in memory and solar cells. At last, we integrated this bio-inspired crystal growth concept with the peptide nanotube detection platform for the development of ultra-sensitive sensors for heavy metal ions. When peptides with high affinity and specificity to bind target metal ions are implemented with electrochemical transducers, the metallization of these ions by the peptide increases the conductivity between electrodes and hence, this conductivity change can be used as the signal for the detection of the heavy metal ion. The compact design and inexpensive fabrication of the sensor combined with the electrochemical transduction for an easy integration with the circuitry make this sensor an excellent alternative for the in-field detection of ultra-low levels of toxic heavy metal ions
5:00 PM - NN3.7
Synthetic Calcite Spicules with Waveguiding Properties.
Wolfgang Tremel 1 , Filipe Natalio 1 , Timo Schueler 1 , Xiahong Wang 2 , Werner Steffen 3 , George Fytas 3 4 , Werner Mueller 5 , Heinz-Christoph Schroeder 5
1 Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universität, Mainz Germany, 2 National Research Center for Geoanalysis, Tsinghua University, Beijing China, 3 , Max Planck-Institut für Polymerforschung, Mainz Germany, 4 Materials Science and Technology, IESL-FORTH , Heraklion Greece, 5 5Institut für Physiologische Chemie, Johannes Gutenberg Universität, Mainz Germany
Show AbstractSelf-assembly and biomineralization are used in biology for the fabrication of many composite materials. Hexactinellida of the phylum Porifera, the so-called glass sponges of the deep sea, are a prominent example of such a composite containing multiple levels of hierarchical organization. At the lowest level of this hierarchy is the organization of an organic axial filament with respect to silica nanoparticles. This axial filament consists predominantly of silicatein, an enzyme that catalyzes the synthesis of biosilica and additional proteins involved in silica formation. Consolidated silica nanospheres are arranged in about 40 well-defined concentric siliceous layers glued together by an organic matrix to laminated fibers. The assembly of these fibers into bundles, mediated by the laminated silica-based cement, results in the formation of a macroscopic cylindrical cage-like structure reinforced by diagonal ridges. The ensuing design overcomes the brittleness of glass, its principal constituent, and shows excellent mechanical rigidity and stability. Besides their skeletal function these stratified spicules act as optical glass fibers with high- and low-pass filter function, suggesting that they might be involved in a photoreception system.We report the fabrication of 1D fibers made of calcium carbonate (CaCO3). The formation of the synthetic calcitic spicules reported here is mediated by silicatein, a protein that has an inhibitory effect on the development and growth of CaCO3 crystals by interacting with specific faces at its early stages of mineralization leading to the formation of small calcitic crystallites with diameters between 5 and 8 nm. Interestingly, when silicatein is adsorbed, these nanocrystals organize in a unique fashion through protein-protein hydrophobic interactions into a polycrystalline microstructure with a needle-like morphology, a length of several hundred micrometers and an aspect ratio of about 10000 with preferential directional growth. The calcitic wires exhibit a remarkable morphological and structural similarity to Sycon spp. calcitic sponge spicules suggesting an evolutionary homologous biomineralization process that bridges Demosponge and Calcarea classes. An intrinsic photoluminescence with waveguiding properties makes them promising candidates for effective and low-loss waveguide components in the micro- and nanometer range.Free space coupling of laser light was used to study the wave-guiding properties of the spicules and to demonstrate that they are remarkably similar to comercial optical fibers and capable of forming an effective fiber-optical network.
5:15 PM - NN3.8
Synthesis of CuS Wires and Polygonal Crystals on Structured Surfaces.
Yolanda Vasquez 1 , Joanna Aizenberg 1 , Erin Fenton 2 , Victoria Chernow 1
1 Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts, United States, 2 Center for Biomedical Engineering and Department of Chemical and Nuclear Engineering, NMSU, Albuquerque, New Mexico, United States
Show Abstract Copper sulfides have been studied for many years as a potential material for optoelectronic devices and for applications in photovoltaics. Micron scale polymer nanopost arrays were fabricated and rendered superhydrophobic to serve as microenvironments for the crystallization of covellite type Copper Sulfide (CuS). The tips of the posts serve as nucleation sites for the growth of wires (20 µm long and 200-300 nm in diameter) and kinked structures or "polygons". The crystallites were characterized by TEM, SEM, and XRD. From time point experiments, the mechanism resembles that of oriented attachment which is prevelant in formation of mesocrystals in biomineralization.
5:30 PM - NN3.9
Bioinspired 3D Reinforced Composites.
Randall Erb 1 , Rafael Libanori 1 , Andre Studart 1
1 Dept. of Materials/Complex Materials Group, Swiss Federal Institute of Technology - ETH Zürich, Zürich Switzerland
Show AbstractNatural composites like seashells combine soft organic and hard inorganic materials to exhibit both strength and toughness. Additionally, the seashell showcases unique orientation of its inorganic reinforcement to provide significant out-of-plane strength in the third dimension that is not typical in similar planar structures1. 3-D reinforcement remains a challenge in artificial composites due to the limited orientational control of the reinforcing particles. The absence of reinforcement in the out-of-plane direction provides weak compression strengths and often leads to delamination in man-made composites. We report a new method to deliberately control the orientation of reinforcing particles in polymer matrix composites. In this method, magnetic nanoparticles (<0.01vol%) are first attached to the nonmagnetic reinforcing particle of interest via electrostatic forces. The coated reinforcing particles are then suspended in a polymer precursor solution that is subsequently cast on a flat substrate. The application of a low magnetic field in the range 5-500 Gauss leads to effective orientation of the reinforcing particles in the polymer solution. Surprisingly, the field required for orientation is so low that it can even be applied with handheld magnets. The reinforcing particles in the films can be homogeneously distributed or can be locally concentrated using magnetic field gradients. Using this novel processing route, we have prepared a family of advanced composites that exhibit three-dimensional reinforcement and unique mechanical properties. For example, a 9-fold and 3-fold increase were obtained in compressive elastic modulus of polyurethane films containing platelets aligned out-of-plane, as compared to pure polyurethane films and films containing in-plane aligned platelets, respectively. Films exhibiting different platelet orientations can also be combined into layered assemblies of vertical and horizontally reinforced structures similar to those found in seashells and teeth. The resulting bioinspired composite is expected to show an unusual combination of out-of-plane stiffness on the surface and high toughness in the inner layer. References:[1] Bonderer, L. et al. Science 319 (5866) 1069-1073, 2008.
5:45 PM - NN3.10
Size Reduction of Egg Shell Particles: The Effect of Ball Milling and Sonication Time Variation.
Vijaya Rangari 1 , Tarig Hassan 1 , Shaik Jeelani 1 , Rohit Rana 2
1 Materials Science and Engineering, Tuskegee University, Tuskegee, Alabama, United States, 2 Nanocenter, IICT, Hyderabad, Andhrapradesh, India
Show AbstractTarig A. Hassan1, Vijay K. Rangari1, Shaik Jeelani1 and Rohit K. Rana21 Tuskegee University’s Center for Advanced Materials (T-CAM), Tuskegee, AL 360882 Indian Institute of Chemical Technology, Hyderabad, IndiaABSTRACTRecently researchers have shown great interest in synthesizing environmental friendly “green” inorganic materials using bio inspired routes. These bio based nanoparticles are used as fillers in improving material’s physical, mechanical, thermal and chemical properties and will reserve. In this study a novel technique is developed to produce calcium carbonate nanoparticles (CaCO3) from eggshells. Mechanical attrition and sonochemical cavitation methods were used in the size reduction of eggshell materials. Eggshells were cleaned and dried then ball milled in a liquid poly propylene glycol for different times. Milling time was varied from one hour to ten hour to obtain fine particles. Followed the ball milling, fine eggshell particles were irradiated with a high intensity ultrasonic horn (Ti-horn, 20 kHz, and 100W/cm2) at room temperature in the presence of an organic solvent.. DMF, Decalin and THF solvents were used in the sonication process and the sonication times were varied by one hour from one to five hours. The as-prepared bio nanoparticles were tested for their size, structure, surface area and pore size and volume. These bio-nanoparticles will be used as the reinforcing filler in thermoplastic and thermoset polymer to fabricate bio-nanocomposite materials for structural applications in electronic, automotive, aerospace and other military application. The advantages and disadvantages of the synthesis processes have been investigated.
NN4: Poster Session
Session Chairs
Wednesday AM, December 01, 2010
Exhibition Hall D (Hynes)
9:00 PM - NN4.1
Structure and Composition Analysis of an Ultra-hard Magnetic Biomineral in Chiton Radular Teeth.
Michiko Nemoto 1 , Qianqian Wang 1 , Brian Weden 1 , Shinobu Heier 2 , David Kisailus 1
1 , University of California, Riverside, California, United States, 2 , Thermo Fisher Scientific, West Palm Beach, Florida, United States
Show AbstractThrough the course of evolution, nature has evolved efficient strategies to synthesize inorganic materials that demonstrate desirable mechanical properties. These biological systems demonstrate the ability to control nano- and microstructural features that significantly improve mechanical properties of otherwise brittle materials. The fully-mineralized radular teeth of chitons is one of such example of a superior biomineral consisting of a brittle, magnetic iron oxide crystal. Chitons are a group of herbivorous marine mollusks that have evolved ultra-hard and damage-tolerant teeth to graze upon algae growing on and within rocky substrates. Our results from nano-indentation analyses of the teeth of chiton (Cryptochiton stelleri), indicated that it retained largest hardness and stiffness properties of any biomineral. In order to understand the relationship between composition, structure and mechanical properties of the fully mineralized radular teeth, we further conducted detailed structural and compositional analyses of this magnetic biomineral using various microscopy and spectroscopy techniques. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses revealed the rod-like orientation of the magnetite crystallites in the teeth. Furthermore, chitin, a polysaccharide found in the exocuticles of many insects, was detected from the teeth by infrared and raman spectroscopic analyses. We believe that the combination of this organic matrix and hard mineral, constructed in a unique microstructure, yields a damage-tolerant, ultra-hard, magnetic biomineral.
9:00 PM - NN4.10
Novel Artificial Polypeptides with Ability of Silicate Precipitation.
Ippei Fujiyama 1 , Yusuke Matsuda 1
1 Bioscience, Kwansei-Gakuin University, Sanda, Hyogo, Japan
Show AbstractPolypeptides and some biopolymers such as Silaffin and long chain polyamines from diatom shell are known to promote a precipitation of silicic acid in vitro under modest conditions of room temperature, neutral pH, and atmospheric pressure. Clusters of positively charged side-chains or groups are found to occur commonly in these Si biomineralizing molecules. This observation prompted us to create artificial polypeptides using a template polypeptide derived from C-terminus region of a chloroplastic carbonic anhydrase, PtCA1, in the marine diatom Phaeodactylum tricornutum. PtCA1 is localized in the pyrenoid of the chloroplast forming large particles and this complex forming capacity is previously ascribed to the function of the C-terminal amphipathic helix of this enzyme, in which hydrophobic residues emerged every three amino acid. In this study, we introduced basic amino acids in appropriate positions in this amphipathic helix by site-directed mutagenesis to create novel basic polypeptides, which we termed Cationized-Diatom Pyrenoid Forming Factor (CDPF). CDPF constructs were packaged into the expression vector pMAL-p2 and transformed to Escherichia coli TB1 (K12 strain). A lysine type CDPF1 exhibited rapid silica precipitation activities in the presence of 100 mM silicic acid and 80 mM phosphate. Precipitated silica observed under SEM exhibited a spherical ball shaped particles of 300~500 nm. The size of silica ball was highly dependent of CDPF1 concentration and decreased to less than 10 nm as decrement of [CDPF]. These results indicate that newly created CDPF peptide which has both hydrophobic and basic clusters in parallel on one helical structure functions efficiently to precipitate silicate. Details of CDPF1 reaction will be discussed.
9:00 PM - NN4.11
Preparation of Organic-inorganic Liponano-capsules via the Counter-diffusion of Ions Across the Capsule Wall.
Yuuka Fukui 1 , Keiji Fujimoto 1
1 , Graduate School for Science and Technology, Keio University, Yokohama, Kanagawa Prefecture Japan
Show AbstractIntroduction: We employed the layer-by-layer (LbL) deposition of organic biomaterials such as polypeptides and polysaccharides and calcium phophate (CaP) as an inorganic biomaterial on a liposome to produce hybrid nanocapsules (liponano-capsules). In this study, we tried to conduct the controlled precipitation of CaP on the liposome surface and polysaccharide-coated nanocapsules by tuning composition of the capsule wall and reaction conditions such as temperatures and pH. Our aim is that such control in precipitation of CaP over the nanocapsule surface would provide a hybrid nanocapsule with osteoconductivity, bio-inertness, and pH-responsivity. The releasing behaviour and the site-specific targeting of liponano-capsules were also investigated to expand their capability as delivery carriers. Materials and methods: A negatively-charged liposome with the diameter of 100 nm was prepared through combination of freeze-thawing and membrane-extrusion using dilauroyl phosphatidic acid (DLPA) and dimyristoyl phosphatidylcholine (DMPC). Alternative deposition of chitosan (CHI) as a cationic polysaccharide and dextran sulphate (DEX) or DNA as an anionic polysaccharide was conducted onto the liposome surface. We here intended to control production of calcium phosphate (CaP) using nanocapsules as a template for the reaction of calcium ions and phosphate ions. Calcium ions and phosphate ions were compartmentalized into the outer phase and the inner cavity, respectively, to enable the spatial control of CaP formation over its surface via the counter-diffusion of ions across the lipid membrane. Moreover, a “field” for precipitation of CaP on the capsule wall was provided by selection of polysaccharides with the affinity for calcium ions and/or phosphate ions in terms of versatile designs and optimization towards mineralization. As an approach to biomedical applications, we investigated pH-triggered release of DNA from CaP-coated liposome upon dissolution of CaP. Results and discussion: TEM observation showed that the capsule wall of CaP was formed selectively over the surfaces of bare liposomes and DNA-coated nanocapsules by controlling the counter-diffusion of ions, whereas no CaP formation occurred on the surfaces of CHI-coated and DXS-coated nanocapsules probably due to the low affinity of the capsule surface with ions and CaP. From the results of electron diffraction analysis, the CaP wall over the DNA-coated nanocapsules showed higher crystallinity than that over the surface of liposomes. By changing ion species for CaP formation, the wall of CaP could be produced on CHI-coated nanocapsules. We prepared lipo-CaP-DNA by adsorption of DNA onto the CaP-coated liposome and its pH-triggered release of DNA could be observed due to dissolution of CaP at low pH. We are currently studying optimization of the CaP wall towards the bone-targeted delivery system and the gene delivery system.
9:00 PM - NN4.12
Dissolution Kinetics of Type B Carbonate Apatite Sintered Body.
N. Watanobe 1 , T. Yoshioka 1 , T. Ikoma 1 , T. Kuwayama 2 , T. Higaki 2 , J. Tanaka 1
1 Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology, Tokyo Japan, 2 , Kuraray Medical Inc., Okayama Japan
Show AbstractCarbonate apatite (CAp) is a main inorganic component in bone tissue, in which the carbonate content is 2.3 – 8 wt%. According to substitution sites of carbonate ions into hydroxyapatite (HAp;Ca10(PO4)6(OH)2), the A- (OH-) and B- (PO43-) type CAps have been reported. Gibson et al. described a sintered body of AB-type CAp at lower sintering temperature than HAp to improve the lower biodegradation[1]. The advantages of B-type CAp against HAp are higher solubility in vivo with lower crystallinity compared with A-type CAp and excellent biocompatibility. Furthermore, it has a possibility to control biodegradation rate to change the carbonate contents accompanying with substitution of sodium ions into calcium site of HAp. In this study, we evaluated the sintering process of B-type CAp with differently synthesized CAp powders, and investigated biodegradation rate against the substitution amounts of carbonate and sodium ions. The B-type CAp was prepared by a wet method using Ca(OH)2 suspension and H3PO4 solution including Na2CO3, NaHCO3, and CaCO3 as carbonate sources. From X-ray diffraction measurements, the precipitates were identified as a low crystalline and single phase of apatite. Fourier transform infrared spectra showed that the carbonate ions in apatite obtained was ascribed to the B-type substitution of which amount was determined to be 2 - 10 wt% with a thermogravimetry. The elemental analysis with inductively coupled plasma spectroscopy indicated that the CAp powder using different sodium sources contained about 0.10 - 1.77 wt% of sodium. These results suggested that the sodium ions substituted into calcium site play a charge compensating role for carbonate substitution. The precipitates were mixed with polyvinylalcohol and were uniaxially pressed under the pressure of 98 MPa. The green bodies were then sintered at 700-1200°C in the air. The relative densities of the sintered CAp bodies below 900 °C were relatively larger than those of pure HAp. It suggested that sodium ions could increase the relative density. The discs were immersed in 50mL of 0.08M sodium acetate buffer (pH 5.5) at 25°C for 300min with stirring. The dissolution rates of the CAp discs increased with increasing carbonate and sodium contents. It is concluded that the B-type CAp is a good candidate of biodegradable artificial bone materials.[1] I. R. Gibson and W. Bonfield, J. Biomed. Mater. Res., 59, 697 (2002).
9:00 PM - NN4.13
In vitro Evaluation of Osteogenic Activity of Testosterone Associated to Composites of Biodegradable Polymers into Bioceramic Matrix
Maria Cortes 1 , Kelen Costa 1 , Celia Lanza 3 , Ruben Sinisterra 2 , Joel Passos 2 , Alinne Gomes 2
1 Restorative Dentistry, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil, 3 Cirurgic, Phatology and Clinic, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil, 2 Chemistry Department, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
Show AbstractBioceramic / polymer composites are promising materials for biomedical applications, as they combine the bioactivity of bioceramics with the elasticity of polymers. Furthermore, the Testosterone which is a natural androgen hormone was associated to that composite, in order to play an important role related to the maintenance of the bone mass. Composites scaffolds of polycaprolactone (PCL), poly(lactic acid-co-glycolic acid) (PLGA), bioceramic (BC) (1:3) loaded 10 (wt%) testosterone (T) have been prepared and characterized by FTIR and DRX. The FTIR characteristic spectrums of starting substances are presented in the composites. Results by FTIR verified the presence of the evidence of a new material formation. The PCL/BC and the PCL/BC/T X ray diffractograms composites revealed a crystalline profile; the PLGA//PCL/BC and the PLGA/PCL/BC/T, were amorphous. Osteoblasts were cultivated on PCL/BC, PCL/BC/T, PLGA/PCL/BC and PLGA/PCL/BC/T scaffolds. The adhesion, viability and the cells proliferation were evaluated through SEM and MTT assay, respectively. Osteoblast cells attached to all devices with or without T demonstrating the greatest cell growth. The cell viability and proliferation were significant increased proportionally with the time in the presence of composites loaded T compared to composites without T. After that, the metabolic activity provided by the alkaline phosphatase was evaluated through the BCIP-NBT assay. The alkaline phosphatase produced by osteoblasts cultured with PLGA/PCL/BC/T composite revealed better metabolic activity after 72 h. The testosterone addition had a strong influence in the cellular response related to viability and proliferation. Taken the set of results have been suggesting that the PLGA/PCL/BC/T composite would be well indicated as a device to be applied to the bone tissue engineering.
9:00 PM - NN4.14
Electroless Deposition of Pd and Pt Metal Nanoparticles on Self-asembled Rosette Nanotubes.
Rahul Chhabra 1 2 , Jae-Young Cho 2 , Hicham Fenniri 1 2
1 Chemistry, University of Alberta, Edmonton, Alberta, Canada, 2 , National Institute for Nanotechnology, Edmonton, Alberta, Canada
Show AbstractSelf-assembled rosette nanotubes (RNTs) are a new class of biocompatible materials which are obtained from the self-assembly of a DNA base analogue called the G^C motif.1 In previous studies, we have demonstrated that lysine-functionalized RNTs can nucleate 1.4 nm Au nanoparticles in a well-ordered fashion.2 In order to expand the scope of this study, we are now investigating the formation of platinum and palladium nanoparticles on the RNTs to construct novel RNT-noble metal hybrid materials. These are of particular interest due to their potential for catalysis in an aqueous environment along with numerous applications in nanoelectronics and optics. Interestingly, we have observed that both fresh and aged RNT solutions have the ability to reduce Pt and Pd metal salts to form metal nanoparticles in the absence of reducing agents. Detailed investigations of this reduction process and characterization of the nanomaterials will be presented. 1. Fenniri, H.; Mathivanan, P.; Vidale, K. L.; Sherman, D. M.; Hallenga, K.; Wood, K. V.; Stowell, J. G. J. Am. Chem. Soc. 2001, 123, 3854.2. Chhabra, R.; Moralez, J. G.; Raez, J.; Yamazaki, T.; Cho, J.-Y.; Myles, A. J.; Kovalenko, A.; Fenniri, H. J. Am. Chem. Soc. 2010, 132, 32.
9:00 PM - NN4.15
Understanding the Role of Chemical Functionalities on the Mediation of Calcium Phosphate Biomineralization.
William Miles 1 , Sheng Lin-Gibson 1
1 , NIST, Gaithersburg, Maryland, United States
Show AbstractRecent studies have shown that peptides containing contiguous acidic moieties (i.e., polyaspartic acid) promote interfibrillar mineralization of collagen, leading to structures similar to those observed in bone formation. Similar acidic moieties in contiguous glutamic acid sequences have been identified as the active sites for nucleating hydroxapatite in proteins. Studies have also indicated that for biomineralization proteins where a mineral interaction domain has been identified, the mineral interaction domain apparently adopts an extended structure or ‘random coil’ in solution, suggesting the peptide secondary structure has minimal effect on the mineralization process. However, mineralization of calcium phosphate by molecules containing only carboxylate functional groups does not generally lead to appreciable mineralization or evidence of interfibrillar mineralization. As such, the exact mechanism for acidic peptide-mediated biomineralization remains elusive. This research seeks to elucidate the effects of the specific functional groups on the nucleation of calcium phosphate through the incorporation of polyelectrolyte additives. Carboxyl, primary amine, secondary amine, quaternary ammonium, and poly(amino acid) functional groups were selected as model systems to determine the role of charge and basicity on the nucleation of calcium phosphate. The mineralizing solution consisted of calcium chloride (CaCl2) and potassium phosphate dibasic (K2HPO4) in tris-saline buffer exposed to different polyelectrolytes, and nucleation induction times were determined using dynamic light scattering and the calcium activity was monitored with a calcium ion selective electrode. The resulting particles were image via transmission electron microscopy. As expected, acid groups (particularly carboxylic acids) inhibited nucleation through chelation of calcium ions. Unexpectedly, we found that additives containing only secondary amines significantly catalyzed nucleation, while additives containing only primary amines were found to significantly inhibit nucleation. Additionally, additives containing primary amines showed a significantly larger affinity to the calcium phosphate surface and inhibited crystal growth once nucleation had occurred. Additives containing quarternary ammonium functional groups had no effect on the nucleation kinetics. These results indicate 1) charge alone does not appear to affect the nucleation kinetics significantly, and 2) both the functionality and the calcium phosphate affinity of a specific functional group affects calcium phosphate mineralization behavior. Research is ongoing to determine how various functionalities affect mineralization in the presence of collagen as well as model surfaces. This work is supported by a NIDCR/NIST Interagency Agreement Y1-DE-7005-01.
9:00 PM - NN4.16
A Study on the Physico-Chemical and Biological Properties of Mongol-Altai Moomiyo
Munkhjargal Anu 1 , Jigjiddorj Alimaa 2 , Dashzeveg Rentsenmyadag 1 , Chimed Ganzorig 1
1 Center for Nanoscience and Nanotechnology and Department of Chemical Technology, Faculty of Chemistry, National University of Mongolia, Ulaanbaatar Mongolia, 2 , Monenzyme Research and Production LLC, Ulaanbaatar Mongolia
Show AbstractMain objectives of our study are to determine the physico-chemical and biological properties of Moomiyo (Tibetan nomenclature: brag shun).Moomiyo is an “exudate” that oozes out of cracks in the Mongol Altai rocks and cliffs in the summer months. It is composed of organic plant material that is thought to have been compressed by rock for thousands of years. After it is collected, it is naturally purified and processed into a potent, high-quality extract.Moomiyo is extremely rich in plant-source organic minerals, contains more than 40 kinds of complexed minerals and trace elements. Moomiyo is astoundingly rich in nutrients, antioxidants, amino acids, and anti-bacterial, anti-viral and anti-fungal phytochemicals.The main active components in Moomiyo are macromolecules known as fulvic acids. Mongol-Altai mountain Moomiyo contains up to 19% of fulvic acids. Fulvic acids are one of nature’s most astounding and miraculous molecular substances, perhaps rivaling DNA in its importance to life on this planet. The mixture of humic and fulvic acids has proven to be a powerful organic poly-electrolyte antioxidant in nature.Morphological study of raw materials containing moomiyo is studied using atomic force microscopy and scanning electron microscopy, and the elemental analysis is performed using X-ray diffraction spectrometer.Spray dried extract of Moomiyo is examined by using molecular spectroscopic techniques such as UV-visible spectroscopy, infra-red spectroscopy as well as gas chromatography-mass spectroscopy. Biological properties including antibacterial property is studied by using general microbiological techniques.
9:00 PM - NN4.2
Controlled Fabrication of Moth Eye Mimetic Nanopillar Arrays and Their Optical Properties.
Hyuneui Lim 1 , Seungmuk Ji 1 , Wan-Doo Kim 1
1 Nature inspired mechanical systems, Korea institute of machinery and materials, Daejeon Korea (the Republic of)
Show AbstractThe 2-D periodic nanopillar array is a great potential in a 2-D grating and a photonic crystal waveguide. In nature, the moths have these arrays on corneal surface of eye as antireflective surfaces to prevent themselves from the attacking of predator. We demonstrate that moth eye mimetic transparent 2-D periodic nano-pillar arrays on quartz by plasma etching technique using colloidal nanoparticles mono-layer as a mask. This technique called colloidal lithography is controllable and simple lithographic technique due to simplicity of mask pattern generation. The control of size, height and shape of nano-pillars is performed by adjusting size of nanoparticles and etching conditions to investigate the influence of nano-pillar structure on optical properties.It is found that the light scattering is increased at visible range depending on the height and size of nanopillar even though the size of nanopillar is smaller than the wavelength of the incident light. The reflectance spectrum shows red shift with increase of the height of nanopillar owing to the increasing optical interface. Therefore, the color of reflected light on moth eye surface controlled by adjusting height of nano-pillar is exhibited for the applications on wavelength selective LED or solar cells.
9:00 PM - NN4.3
Self-assembly Organic-inorganic Hybrid of Porphyrin Rod or Oxyanions by Water-soluble Building Blocks of Magnesium Phyllosilicate.
Young-Chul Lee 1 , Ji-Won Yang 1
1 Chemical & Biomolecular Engineering, KAIST, Daejeon Korea (the Republic of)
Show AbstractLayered inorganic-organic composite materials based on 2:1 trioctahedral phyllosilicates have been synthesized and characterized for a variety of applications, such as ion exchange, catalysis, and the construction of nanoscale assemblies. Recently, several reports on the synthesis and characterization of organically-modified derivatives of magnesium phyllosilicate have appeared because of their wide applicability in areas such as wrapping of biomolecules and drug delivery system. This hybrid material are members of a family of 2:1 organo-modified trioctahedral phyllosilicates with structures similar to that of natural talc and has unique properties because this organoclay composed of water-soluble cationic organic building blocks in water media, resulting in self-assembled with negative charged organic or inorganic materials owing to high density of amine functional group of organoclay. Herein we tried wrapping of porphyrin rod, which was meso-tetrakis(4-sulfonatophenyl)porphyrine (TPPS) units induced porphyrin rod structure (J-aggregate, below pH 4), stabilized with magnesium phyllosilicate (organoclay) due to electrostatic interaction. Constructs with J-aggregate by organoclay itself and oligomer (low molecular weight) of organoclay showed different sheathed morphology and steric effect with retention of optical property. Beyond to application of organic materials, this organoclay was used for wrapping of toxic pollutants with oxyanions such as As, Cr, CN by self-assembly process for water-treatment. Within a few minute, all oxyanions were precipitated and showed high removal capacity compared with other adsorbents reported. Therefore, this nanoscale assembly using this organoclay will be suggested a novel removal means for negative charged environmental contaminants as water-treatment as well as increase in stability of organic/biomaterials.
9:00 PM - NN4.4
WITHDRAWN 11/09/10 New Salts of Amino Acids with Dimeric Cations.
Vahram Ghazaryan 1 , Michel Fleck 2 , Aram Petrosyan 1
1 , Institute of Applied Problems of Physics, Yerevan Armenia, 2 , Institute of Mineralogy and Crystallography, University of Vienna, Vienna Austria
Show AbstractAmong salts of amino acids there are compounds with the composition 2A.HX, which consist of dimeric A...A+ cations with short symmetric or asymmetric hydrogen bonds between zwitter-ionic and protonated moieties. Phase transitions of different nature are possible as a result of the variation of temperature and/or pressure. The best-known example is diglycine nitrate, which is ferroelectric below phase transition temperature. Salts of optically active amino acids that enforce noncentrosymmetric crystal structures are interesting also as nonlinear optical materials. In the present contribution we report the preparation of 20 new salts with dimeric cations from aqueous solutions, including compounds of glycine [2Gly.HBF4 (P-1, Z=6), 2Gly.HClO4 (P-1, Z=10)], betaine [2Bet.HBF4 (C2/c, Z=4)], β-alanine [2β-Ala.HBr (C2/c, Z=4), 2β-Ala.HBF4 (C2/c, Z=4)], L-phenylalanine [2L-Phe.HCl, 2L-Phe.HBr (P21, Z=4), 2L-Phe.HBF4, 2L-Phe.H2C2O4 (a=5.555(1)Å, b=13.530(3)Å, c=14.646(3)Å, α=71.98(3)°, β=88.04(3)°, γ=86.75(3)°, P1, Z=2), 2L-Phe.H2SeO3 (a=11.0507(4)Å, b=12.8611(5)Å, c=12.8611(5)Å, α=107.867(2)°, β=110.392(2)°, γ=90.017(2)°, P1, Z=4)], L-alanine [2L-Ala.HCl (a=5.084(1)Å, b=19.371(4)Å, c=10.958(2)Å, β=90.217(4)°, P21, Z=4), 2L-Ala.HBr], L-threonine [2L-Thr.HCl], L-valine [2L-Val.HCl, 2L-Val.HBr (a=11.480(1)Å, b=5.222(1)Å, c=12.062(1)Å, β=96.776(4)°, P21, Z=2)], L-leucine [2L-Leu.HBr (a=11.529(1)Å, b=5.247(1)Å, c= 15.105(1)Å, β=108.032(4)°, P21, Z=2), 2L-Leu.HClO4)] and L-proline [2L-Pro.HCl (a=b=12.8188(4)Å, c=16.0876(7)Å, P41212, Z=8), 2L-Pro.HBr (a=b=12.8482(6)Å, c=16.4126(7)Å, P41212, Z=8), 2L-Pro.HBF4 (a=16.4126(7)Å, b=7.3654(4)Å, c=12.6730(9)Å, b=90.088(1)°, P21, Z=2)]. The prepared salts are characterized by IR and Raman spectroscopy. Some of them are grown in form of good quality single crystals, which allowed the determination of their crystal structure. For noncentrosymmetric phases, the nonlinear optical activities are assessed by second harmonic generation powder tests.
9:00 PM - NN4.5
WITHDRAWN 11/09/10 Mixed Salts of Amino Acids as a Mine of New Materials.
Vahram Ghazaryan 1 , Michel Fleck 2 , Aram Petrosyan 1
1 , Institute of Applied Problems of Physics, Yerevan Armenia, 2 , Institute of Mineralogy and Crystallography, University of Vienna, Vienna Austria
Show AbstractOver the last years salts of several amino acids (L-arginine, L-histidine, etc.) have been intensively investigated as nonlinear optical (NLO), pyro- and piezoelectric materials. These compounds represent simple salts, i.e. they contain only one definite type of anion. Mixed salts of amino acids with different anions are of considerable interest not only from chemical and structural points of views, but also in regard to the properties that can be controlled by appropriate choice of anions. Several properly characterized mixed salts of amino acids have been obtained and described, viz. (L-Lys+...L-Lys2+).2Cl(-).ClO4(-) [1], (L-Lys+...L-Lys2+).2Cl(-).NO3(-) [2]), 2L-Orn2+.Cl(-).NO3(-).SO4(2-) [3], irrespective of their NLO properties. Fifteen possible formation mechanisms of mixed salts of amino acids were proposed, including two mechanisms discovered in [1-3]. Using them as a guide we obtained more than 30 new mixed salts of L-arginine, L-histidine, L-lysine, L-ornithine, formed by eight mechanisms, including two known [1-3] out of the fifteen proposed: 2A+.X(1).X(2), 3A+.2X(1).X(2), A2+.X(1).X(2), 2A2+.2X(1).X(2).X(3), 2A2+.3X(1).X(2), 2A2+.X(1).X(2).Y(2-), 2A2+.2X.Y(2-), (A+...A2+).2X(1).X(2). A+ and A2+ are singly and doubly charged cations of above mentioned amino acids, X stands for different anions (F, Cl, Br, NO3, BF4,ClO4) and Y(2-) is SO4(2-). The obtained crystals have been characterized by IR and Raman spectra. The crystal structures have been determined for salts grown in form of single crystals with good quality. The preliminary examination by powder second harmonic generation tests showed that the following crystals: L-His2+.NO3(-).BF4(-), L-Arg2+.NO3(-).F(-), L-Arg2+.NO3(-).BF4(-) β-form, L-Lys2+.Cl(-).BF4(-), L-Arg2+.NO3(-).ClO4(-) γ-form, 2L-Orn2+.2Cl(-).SO4(2-) and 2L-Orn2+.Cl(-).NO3(-).SO4(2-) display strong SHG.[1] N. Srinivasan, B. Sridhar, R.K. Rajaram, Acta Crystallogr. E57, o875-o877 (2001).[2] N. Srinivasan, B. Sridhar, R.K. Rajaram, Acta Crytallogr. E57, o888-o890 (2001).[3] S. Ramaswamy, B. Sridhar, V. Ramakrishnan, R.K. Rajaram, Acta Crystallogr. E60, o768-o770(2004).
9:00 PM - NN4.6
WITHDRAWN 11/09/10 Nonlinear Optical Crystals Based on L-nitroarginine and L-nitrohistidine.
Ruben Apreyan 1 , Hayk Petrosyan 1 , Armen Atanesyan 1 , Aram Petrosyan 1
1 , Institute of Applied Problems of Physics, Yerevan Armenia
Show AbstractOver the last years, crystalline salts of L-arginine and L-histidine have been intensively investigated as nonlinear optical (NLO) materials. One may expect that L-nitroarginine and its salts will show stronger NLO properties than L-arginine due to the introduction of an electron-acceptor nitro group, in addition to the existing electron-donor amino group. However, contrary to expectation, the NLO activity of L-nitroarginine (L-NNA) and its known L-NNA.HCl.H2O crystalline salt [1] turned out to be lower than that of L-arginine (L-Arg) and L- Arg.HCl.H2O. For clarification of the reasons we investigated L-nitroarginine and its salts in more detail. We discovered a new crystalline form of L-nitroarginine (β-form L-NNA), which in contrast to known powdered form (designated by us as α-form) can be obtained in form of single crystals [2]. Determination of crystal and molecular structures showed that β-form of L-NNA has a zwitterionic nitrimine molecular structure and not the nitroamine structure as supposed previously. Moreover, the new β-form of L-NNA shows expected high NLO properties (I2ω/I2ωKDP =10 by SHG powder test). We prepared new salts by reaction of L-nitroarginine with various acids (HBr, HI, HNO3, HIO3, HClO4, HBF4, H3PO4, H2SO4). As in case of L-arginine and L-nitroarginine one could expect that L-nitrohistidine would display higher NLO effects compared to L-histidine. The crystal of L-nitrohistidine is known in form of monohydrate (L-NH.H2O) and its crystal structure has been determined irrespective to its NLO properties [4]. Comparative investigation of L-histidine and L-NH.H2O showed that introduction of nitro group significantly increases NLO activity (I2ω/I2ωKDP=4.3) .[1] N. Okabe, Y. Kohyama, K. Ikeda, S. Sunano, Acta Crystallogr. C50(1994) 2041-2043.[2] R.A. Apreyan, H.A. Karapetyan, A.M. Petrosyan, J. Molec. Structure 874(2008) 187-193.[3] R.A. Apreyan, H.A. Karapetyan, A.M. Petrosyan, J. Molec. Structure 875(2008) 272-281.[4] X. Solans, M. Font-Altaba, Acta Crystallogr. B37(1981) 2111- 2114.
9:00 PM - NN4.7
The Effects of Substrate Conductivity and Patterned-spacing on Protein Self Assembly.
Xiaolan Ba 1 , Elaine DiMasi 2 , Yizhi Meng 1 , Miriam Rafailovich 1
1 Materials Science and Engineering, Stony Brook University, Stony Brook, New York, United States, 2 National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York, United States
Show AbstractPernodet et al (Pernodet 2003) have previously shown that large amounts of protein will adsorb and even self assemble into fibrils on Sulfonated Polystyrene (SPS) coated Silicon wafers, when the degree of sulfonation exceededs 12%. When SPS films, with 33% sulfonation (SPS33) were spun cast onto Si wafers with a 20nm thick layer of Au, only a monolayer of proteins was adsorbed, even though the surface in contact with the protein was unchanged. In order to exclude the possibility that the SPS33 was in a different conformation due to interactions with the different substrates, we also conducted the same experiments where we coated Si wafers of different conductivities with 20nm of SPS33. We found that for conductivities less than 0.005 Ω.cm, similar to metals under ambient conditions, no fibers were formed, whereas fibers formed in all samples with resistivity above C=0.1 Ω.cm. And large fibers formed at C=5×103 Ω.cm. Hence even though the protein solutions were exposed to surfaces with covered with polymer films of identical the charges, and chemical composition, the charge of the substrate determined the protein adsorption. In order to eliminate all other sources, such as incubation temperature, we also made patterned substrates, where an Au grating was imprinted onto Si surfaces. Separate grating were formed with spacing of 20 microns and 2.5 microns, and a single grating where the pattern is continuously reduced from 50microns to 10 microns was also produced. The gratings were all covered with SPS33. The results showed unambiguously that only a single layer adsorbed onto the areas where Au was underneath, and a much larger amount of protein was adsorbed onto the areas where Si was beneath the SPS33 coating. Furthermore, in the large areas, where the Si spacing exceeds 20microns, the standard lattice was observed. As the Si area was decreased the lattice became progressively more distorted, till the protein from a sinusoidal like pattern, which further reduced to a straight wire when the Si segments were below 2.5 microns. All fibers were then exposed to biomineralizing solutions, and the effects of fiber morphology on the biomineralized deposits were explored. These results indicate that substrate image charges, possibly created by the approaching charged molecules, as well as the dielectric constant of the polymer coating can play a role in protein adsorption, as well as templating the biomineralization process.
9:00 PM - NN4.8
Simulating Nucleation and Growth in Calcium Carbonate.
John Harding 1 , Colin Freeman 1 , David Quigley 2 , Mingjun Yang 3 , Susan Stipp 3 , Dorothy Duffy 4
1 Engineering Materials , University of Sheffield, Sheffield United Kingdom, 2 Chemistry, University of Warwick, Coventry United Kingdom, 3 Nanoscience Center, University of Copenhagen, Copenhagen Denmark, 4 Physics and Astronomy, University College London, London United Kingdom
Show AbstractThe nucleation and growth of biominerals is controlled by organic molecules or molecular arrays. This control can determine the mineral phase, orientation of growth and shape of the resulting crystal. For many biominerals, including calcium carbonate, the initial phase is thought to be amorphous, with controlled crystallisation coming later. We show how atomistic simulation can demonstrate these effects. Simulations of nanoparticles of various sizes in water, both alone [1] and in the presence of proteins [2] show the importance of surface interactions in determining the particle phase (and the barrier between phases). Metadynamics simulation methods [3] are used to overcome the problem of reaching the timescales that are typical for nucleation processes. We also use these methods to investigate the mechanism of templating in the growth of oriented calcite crystals on self-assembled monolayers [4]. The results show that the control of the crystal orientation is not simply a matter of epitaxial matching; the flexibility of the chains in the monolayer is of fundamental importance.Individual molecules (proteins, peptides and polysaccharides) can also affect crystal morphology through their binding to various surfaces and steps. We calculate absorption energies of these molecules for a number of cases [4] and demonstrate the importance of the water structure in determining whether or not binding will occur and the configuration of the binding molecule at the surface. We have estimated the entropy of binding using thermodynamic integration for small molecules and show that the most important term comes from the disordering of the water displaced by the binding molecule. However, although this effect is significant (up to 30 Jmol-1K-1 per water molecule displaced), it is not large enough to change basic picture arrived at from consideration of the energy alone. [1] D. Quigley and P.M. Rodger, J. Chem. Phys. 128 (2008) 221101.[2] C.L. Freeman, J.H. Harding, D. Quigley and P.M. Rodger, Angew. Chim. Int. 49 (2010)[3] A. Laio and M. Parrinello, Proc. Nat.Acad. Sci. 99 (2002) 12562.[4] D.Quigley, C.L. Freeman, P.M. Rodger, J.H. Harding and D.M. Duffy, J. Chem. Phys. 131 (2009) 094703.[5] M. Yang, S.L.S. Stipp, and J.H. Harding Cryst. Growth Des., 8 (2008) 4066.
Symposium Organizers
John Harding University of Sheffield
Sheng Lin-Gibson National Institute of Standards and Technology
John Spencer Evans New York University
Kiyotaka Shiba Japanese Foundation for Cancer Research
NN5: Characterization
Session Chairs
Wednesday AM, December 01, 2010
Liberty B/C (Sheraton)
9:30 AM - **NN5.1
Impact of Carboxylated Molecules on Cation Hydration Dynamics:Implications for Calcification.
Laura Hamm 1 , Adam Wallace 2 , Patricia Dove 1
1 Geosciences, Virginia Tech, Blacksburg, Virginia, United States, 2 Earth Science Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show Abstract Biomolecules rich in aspartic acid (Asp) are known to play a role in biomineral morphology and polymorph selection, and have been shown to greatly enhance the growth kinetics of calcite. The mechanism by which these compounds favor calcification may be related to their effects upon cation solvation; dehydration of the cation is considered the rate limiting step for crystal growth and ion hydration dynamics are thought to be important in mineral growth and dissolution processes. To understand the impact of carboxylated molecules on the solvation dynamics of cations, we investigated the influence of Asp on the water exchange rates of cations. The reactive flux method was employed to calculate water exchange rate constants for four biologically relevant divalent cations (Mg, Ca, Sr, Ba). Residence times were also determined directly for Ca, Sr and Ba, ions which have relatively fast rates of water exchange. Exchange rates were then recalculated after introducing Asp into the system. All simulations were carried out with the LAMMPS software employing the TIP3P model of water, CHARMM22 force fields, and ion-water potential parameters from Åqvist. Water exchange rate calculations reproduce the expected solvation trends based on cation radius. The energy barrier for water escape from the primary hydration shell is greatest for Mg and smallest for Ba, and water residence times within the first shell increase in the order: Ba < Sr < Ca < Mg. In the presence of Asp, formation of contact ion pairs (CIP) and solvent separated pairs (SSIP) between Ca, Sr or Ba and a carboxylate group increases the frequency of water exchange events in the primary hydration sphere of the cation. No exchange of waters in the primary sphere of Mg is observed on the time scale of the simulations, regardless of interaction with Asp. The results demonstrate that soluble biomolecules exhibit kinetic effects upon cation solvation and support the idea that carboxylated molecules promote partial cation dehydration.
10:00 AM - NN5.2
Insights into Templated Nucleation of Biominerals.
Michael Nielsen 1 2 , Jonathan Lee 3 , Qiaona Hu 4 , James De Yoreo 1
1 , Lawrence Berkeley Lab, Berkeley, California, United States, 2 , University of California, Berkeley, Berkeley, California, United States, 3 , Lawrence Livermore National Lab, Livermore, California, United States, 4 , University of Michigan, Ann Arbor, Michigan, United States
Show AbstractOne of the challenges in understanding templated growth of biominerals is probing the early events that determine the nucleation pathway and final mineral structure. Much research has been conducted in biomimetic systems using organothiol self-assembled monolayers (SAMs) to template calcite nucleation. Recent studies indicate that in many cases, the formation of oriented calcite in these systems follows a complex pathway involving intermediate phases, and that the SAM structure evolves throughout the process. Despite the many advances in knowledge regarding templated nucleation, important aspects of the process remain poorly understood: a quantitative measure of the energetics of directed nucleation, the interactions between the organic molecules and mineral species, and the structural evolution of incipient nuclei. Here we report the use of a constant composition system to measure calcium carbonate nucleation rates on alkanethiol SAM-templates over a range of supersaturation and to quantitatively determine interfacial energies. We find that the choice of flow rate is critical to ensuring uniform nucleation is obtained and occurs on the template. With increasing supersaturation, we show that the initial phase to form evolves from calcite to vaterite to amorphous calcium carbonate (ACC). We also present in situ transmission electron microscopy (TEM) observations of crystal nucleation and growth in solution at nanometer scale and video rates. This capability is enabled by the combination of a custom designed TEM stage and fluid cell. Significantly, the design of the cell and holder ensures temperature and electrochemical control over the reaction environment, which can be used to initiate processes of interest, such as the onset of crystal nucleation. Moreover, the system allows for direct investigation of templated nucleation because the working electrode sits in the path of the electron beam. Our first results show that calcium carbonate nucleates on the electrode via nanoparticles of what appears to be a metastable precursor phase — most likely ACC — followed by consolidation and faceting of the crystalline mass. Finally, we report insights from the use of synchrotron-based near-edge X-ray absorption fine structure spectroscopy (NEXAFS) into the evolution of the SAM during the nucleation process. Based on measurements of SAM monomer orientation, we argue that the ability of the SAM to reorganize during the nucleation process is a key feature of a successful template.
10:15 AM - NN5.3
Guided Wave and Confocal SERS from Optical Chemical Benches and Photonic Diatoms.
Mark Andrews 1 , Jonathan Hiltz 1 , Bruce Lennox 1 , Farshid Hajiaboli 1 , Gursimranbir Singh 1
1 Chemistry, McGill University, Montreal, Quebec, Canada
Show AbstractThe first part of this talk describes how we use silver nanoparticles grafted to multimode waveguides to explore polarization state selected guided wave surface enhanced Raman scattering (SERS) from adsorbed overlayers of p-mercaptoaniline and 4-mercaptopyridine. Proton binding and base titration can be observed with excellent signal to noise on these optical chemical bench constructs. We then explore the binding of coinage metal nanoparticles to the patterned silica surfaces of the Nizschia pennate diatom. Surface decoration is achieved with a silicon alkoxide thiol grafted to the diatom surface, and the binding of molecular adsorbates can be observed by confocal SERS microspectroscopy. Binding of metal nanoparticles to the diatom alters optical field interactions, and the final part of the talk explores a photonic device exhibiting radial periodic patterning built from the silica frustule of Coscinodiscus Wailesii.
10:30 AM - NN5.4
Internal Nanostructure of the Calcitic Prisms of Atrina rigida Imaged by ADF-STEM.
Lara Estroff 1 , Huolin Xin 2 , Hanying Li 1 , Ellen Keene 1 , Miki Kunitake 1 , David Muller 3
1 Department of Materials Science and Engineering, Cornell University, Ithaca, New York, United States, 2 Department of Physics, Cornell University, Ithaca, New York, United States, 3 School of Applied and Engineering Physics, Cornell University, Ithaca, New York, United States
Show AbstractBiogenic single crystals are known to incorporate biomacromolecules, spurring investigations of how large molecules are distributed within the crystals without significantly disrupting the crystalline lattice. In this work, we use annular dark field scanning transmission electron microscopy (ADF-STEM) and electron tomography to characterize the internal structure of calcitic prisms from Atrina rigida. A focused ion beam (FIB) was used to remove slices parallel to, perpendicular to, and at a 45 degree angle to the long axis (c axis) of the prisms. The images and tomographic reconstructions reveal that disk-like patches of organic materials are incorporated preferentially in the ab plane. Slices taken from the outer edges were compared to slices taken from near the center of the prisms, revealing some differences between the distribution of the organic inclusions with position. We have compared the nanostructure revealed by ADF-STEM to the results of etching experiments with acetic acid, water, and EDTA.
10:45 AM - NN5.5
Characterization of the Fluorescence Resonance Energy Transfer of the Two-dimensional Patterned Photosynthetic Proteins.
Rei Furukawa 1 , Mamoru Nango 3 , Morio Nagata 2 , Shinji Nozaki 1
1 , The University of Electro-Communications, Chofu, Tokyo, Japan, 3 , Osaka City Univeristy, Osaka Japan, 2 , Tokyo University, Tokyo Japan
Show AbstractRecent study of the photosynthetic systems had suggested that the two light harvesting complex (complex structure of dye and protein), LH1-RC and LH2 (LH: Light Harvesting; RC: Reaction Center), are distributed in approximately 100 nm diameter domains inside the two-dimensional plane of lipid bilayer. Plants are being able to photosynthesize from the two wavelength regions that correspond to the each dye species, which are passing the harvested energy towards the reaction center by the fluorescence resonance energy transfer (FRET). In this study, we had artificially fabricated such two-dye distributing surface by using the self-assembling monolayer (SAM) technique and characterized the FRET behavior by the fluorescent microscope. The purpose of this study is to characterize the optimum pattern that enables the most efficient energy transfer between the two dyes.The patterned substrate was fabricated by microfabrication lift-off and SAM techniques. A silicon wafer with oxidized surface was coated with a photoresist in 25 microns square resolution using the positive lithography. After developing the photoresist, 10 nm-thick gold layer was sputtered using the e-beam evaporator. Then, the photoresist was rinsed off with the upper gold layer. The obtained substrate with the gold and silicon dioxide alternative pattern was soaked in a solution of thior-functionalized LH1-RC and carboxyl-functionalized LH2. By the surface bonding reaction between the functional groups and the inorganic materials, LH1-RC and LH2 were placed on top of the gold and silicon dioxide, respectively. LH1-RC and LH2 were isolated from the photosynthetic bacteria in advance. The FRET behavior of the obtained substrate was observed using the fluorescent microscope. As a conclusion, we have succeeded in fabricating a two-dimensional pattern of the two light harvesting complex that were isolated from the photosynthetic bacteria and chemically functionalized at the purpose of fabricating the SAMs. The fluorescent microscopic image had shown the FRET behavior observed from this two-dimensional pattern.
11:00 AM - NN5: Chara
BREAK
11:30 AM - **NN5.6
Structural Analysis of Minerals and Organo-Mineral Interfaces in the Exoskeleton of Corals.
Roland Kroger 1
1 Department of Physics, The University of York, York United Kingdom
Show AbstractTo identify the key processes driving the mineral formation in biological systems such as corals it is necessary to systematically study the microstructure from the atomic to the macroscopic scale. State-of-the-art characterisation techniques in Materials Science such as electron microscopy, focused ion beam and X-ray based methods provide a unique access to the structure and chemistry on the different length scales. The centers of calcification in corallites pose one of the most prominent challenges with respect to a fundamental understanding of the exoskeleton formation process in marine organisms. We will demonstrate that the coral mineralization is determined by different processes thought to be a combination of biotic and non-biotic accretion of calcium carbonate.
12:00 PM - NN5.7
Small-Angle X-ray Scattering Study of Readily Controllable Palladium Nanoparticle Formation on Viral Nanotemplates.
Amy Manocchi 1 , Byeongdu Lee 2 , Hyunmin Yi 1
1 Department of Chemical and Biological Engineering, Tufts University, Medford , Massachusetts, United States, 2 X-ray Science Division, Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractA key challenge in nanotechnology is the precise control of transition metal nanoparticle fabrication in order to harness valuable size specific properties that arise at the nanoscale. However, tailoring these nanoparticles is often difficult due to harsh reaction conditions and effects of capping agents or surfactants. Therefore, there is a critical need for facile routes for controllable nanoparticle fabrication. Biological supramolecules, such as viruses, offer attractive templates for nanoparticle synthesis, due to their precise size and shape. In addition, simple genetic modification can be employed to offer additional functionality with precise spacing. In this work we exploit the specificity of genetically modified Tobacco Mosaic Virus (TMV1cys) for readily controllable palladium (Pd) nanoparticle synthesis via simple reductive metallization. TMV1cys, engineered to display one cysteine residue on the surface of each of over 2000 coat proteins, provides precisely spaced thiol groups for preferential nucleation and growth of Pd nanoparticles. Small-Angle X-ray Scattering (SAXS) was employed to provide a statistically meaningful route to the investigation of Pd nanoparticle size ranges formed on the viral-nanotemplates. Specifically, we examine the size range and thermal stability of Pd nanoparticles formed on surface assembled TMV1cys. Further, we investigate the in situ growth of Pd nanoparticles on TMV1cys in solution to better understand and predict nanoparticle growth on these nanotemplates. Lastly, we compare TMV1cys templated particle growth to Pd nanoparticle growth in the absence of TMV1cys. We show that Pd nanoparticles form preferentially on surface assembled TMV1cys in high density in a broad particle size range (4-18nm). Further, we show that Pd nanoparticles are significantly smaller and more uniform when formed on TMV1cys in solution as compared to Pd particle growth in the absence of TMV1cys. Finally, we provide insight into the fundamental Pd growth mechanism through in depth in situ SAXS analysis. We anticipate that this work will have a broad and significant impact on the use of biological supramolecules for the well-controlled fabrication of nanoparticles for a wide range of applications by providing fundamental information on particle growth.
12:15 PM - NN5.8
Characterization of Peptide-surface Adsorption Free Energy by AFM/SPR Correlation.
Robert Latour 1 , Yang Wei 1
1 Bioengineering, Clemson University, Clemson, South Carolina, United States
Show AbstractTo support the design of peptides to control biomineralization, a basic level understanding of peptide interactions with inorganic surfaces is needed. One of the most fundamental properties that characterizes these types of interactions is the free energy of adsorption (FEA). FEA serves to provide both a quantitative measure of how strongly a peptide interacts with a surface as well as a very important experimental value that can be used to evaluate, modify, and validate empirical force field parameters that are needed to develop molecular modeling methods to accurately simulate peptide-surface interactions. While FEA can be readily measured using surface plasmon resonance spectroscopy (SPR) and quartz crystal microscopy (QCM), the application of these methods is limited to materials that can readily form nanometer-scale thin films over the sensor substrates in order to measure peptide adhesion. This requirement, however, is prohibitive for many types of materials. Other techniques, such as atomic force microscopy (AFM), can be used to directly measure the peptide adhesion force to a much broader range of material surfaces by tethering peptides to the AFM tip, contacting the surface, and then measuring the desorption force (DF) as the tip is pulled away. The interpretation of the AFM force signal, however, is complicated by the fact that it can be very difficult to accurately determine the number of peptides that the force signal corresponds to. The objective of this research was to address these limitations by synergistically combining SPR and AFM to develop a method that can be used to effectively determine FEA for peptide interactions for any microscopically flat surface. To accomplish this, we first characterized peptide adsorption behavior to a large set of functionalized alkanethiol self-assembled monolayer (SAM) surfaces that could be used by both SPR (FEA measurement) and AFM (DF measurement), with AFM performed using a standardized method to maintain constant peptide-probe-tip density. A plot of DF vs. FEA revealed a very strong correlation between these two measurements, thus creating a calibration plot to provide effective values of FEA from AFM data for surfaces not amenable for use with SPR. We have demonstrated the application of this method to measure the effective FEA for peptide interactions with inorganic surfaces such as quartz glass and titania, and these same methods can be applied to determine the effective FEA for peptide interactions with any microscopically flat surface.
12:30 PM - NN5.9
Weibull Analysis of Biaxial Flexural Strength of Polycrystalline Hydroxyapatite.
Xiaofeng Fan 1 , Eldon Case 1 , Fei Ren 3 , Yutian Shu 1 , Robert Friederichs 2 , Melissa Baumann 1
1 Chemical Engineering and Materials Science, Michigan State University, East Lansing, Michigan, United States, 3 High Temperature Materials Laboratory, Oak Ridge National Laboratory, Oak Ridge , Tennessee, United States, 2 Materials Science & Metallurgy, University of Cambridge, Cambridge United Kingdom
Show AbstractThe Weibull modulus is a measure of the scatter in the fracture strength in brittle materials. Thus, the Weibull modulus is an important design parameter for mechanical reliability. In this study, hydroxyapatite powders were cold pressed and sintered to obtain groups of at least 20 specimens per group with fixed volume porosity, P, where for the entire set of specimens tested, P ranged from approximately 0.08 to 0.46. The specimens were then fractured in biaxial flexure using a ring-on-ring (ROR) loading fixture. The observed dependence of the Weibull modulus, m, on porosity, P, will be discussed along with the implications of this behavior for biomedical and other applications.
12:45 PM - NN5.10
Materials and Mechanical Design of the Dynamic, Articulating Armor of the Helmet Urchin, Colobocentrotus Atratus.
Elaine Lee 1 , Ting-Ting Chen 2 , Mary Boyce 2 , Christine Ortiz 1
1 Materials Science and Engineering, MIT, Cambridge, Massachusetts, United States, 2 Mechanical Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractThe helmet urchin Colobocentrotus atratus possesses an unusual reduction in spines so that they form a tiling of millimeter-sized, flattened, polygonal set of aboral porous armor plates, each composed of a single-crystal magnesium calcite-based composite. This study investigates the composition, microstructure, mechanical properties, and ball-and-socket articulation mechanism of the armor plates experimentally and computationally, in relation to its protective mechanical function from predatory threats. The outer galleried stereom mesh (pore size ~ 15 microns, vol. porosity ~ 34%) was modeled using elastic three-dimensional finite element analysis that consisted of a microstructurally-based representative volume element and periodic boundary conditions. Various loading configurations were simulated in order to obtain the anisotropic stiffness tensor. The simulations resulted in an approximately orthotropic effective mechanical behavior with the stiffness in the plane transverse to the long axis of the galleried microstructure (E1, E2) less than the axial direction (E3). Parametric simulations were carried out as a function of the solid volume fraction and E1, E2 were found to decrease with increasing porosity, while E3 increases. Spatial gradients in density were also modeled, whereby the density decreases from the ball-and-socket joint region to the outer surface of the aboral plate and the stiffer axial direction gallery structure is aligned along lines that radiate outwardly from the joint and ends perpendicular to the outer surface of the plate, providing a functional directionality to the microstructural arrangement of the aboral plate. This open-pore structure and trabeculae alignment results in a directional strengthening due to inhomogeneous deformations in the porous structure for resistance against blunt impact and containment of penetration into the surface of the plate.
NN6: Modeling and Simulation
Session Chairs
Wednesday PM, December 01, 2010
Liberty B/C (Sheraton)
2:30 PM - **NN6.1
Multiscale Modelling of Hard-Soft Interfaces in Bio-inspired Composites.
James Elliott 1
1 Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, Cambridgeshire, United Kingdom
Show AbstractOne of the key challenges in the simulation of bio-inspired composite systems is to traverse a sufficiently wide range of time and length scales in order to study the effects of changing microstructure on properties. For example, in the case of bone, the packing of apatite crystals in and around macromolecular collagen bundles involves millions of atoms, whereas the most common treatment for osteoporosis is based on the use of small molecules of order tens of atoms in size. Furthermore, in the mesocrystallization model of biomineralization, it has been proposed that when aggregation of biomineral nanoparticles occurs in the presence of organic additives, the additives may act both to change structure of single particles directly, and also to mediate, indirectly, the interaction between particles. In this talk, we address the challenge of simulating hard-soft interfaces in bio-inspired composite materials using a combination of robust generic methods for describing interactions between organic-inorganic phases, a coarse-grained polymer model for rapid relaxation and exploration of chain conformations, and reverse-mapping of atomistic structures onto coarse-grained models. We consider the aggregation of calcite nanoparticles, both in vacuo and solvated in explicit water, and calculate the free energy of interaction (including all solvent degrees of freedom) between a pair of particles as a function of their separation. We also discuss the role of benzyl alcohol as a coupling agent in controlling the growth of titania on carbon nanotubes.
3:00 PM - NN6.2
Molecular Mechanism of Peptide Binding to Silica Surfaces − Experiment and Simulation.
Hendrik Heinz 1 , Siddarth Patwardhan 2 , Fateme Emami 1 , Rajiv Berry 3 , Carole Perry 2 , Barry Farmer 3 , Rajesh Naik 3
1 Department of Polymer Engineering, University of Akron, Akron, Ohio, United States, 2 School of Biomedical and Natural Sciences, Nottingham Trent University, Nottingham United Kingdom, 3 Nanostructured and Biological Materials Branch , Air Force Research Laboratory, Wright-Patterson AFB, Ohio, United States
Show AbstractWe explain the binding mechanism of several point-mutated peptides in aqueous solution to silica surfaces characterized by adsorption measurements, zeta potentials, and molecular dynamics simulation in all-atomic detail. Molecular simulation confirms a tiered ion exchange mechanism on the silica surface to explain binding in agreement with measurements and yields the same trends in adsorption upon mutation of single amino acids in a larger peptide as in experiment. We explain by thorough conformational analysis using advanced visualization techniques, Ramachandran plots, and computed 1H, 13C, and 15N NMR spectral shifts over periods of 20 ns simulation time in independent simulations how cooperative effects in the peptide cause conformational changes that result in the observed variation in adsorption energy as a function of the peptide sequence. Single adsorbed peptides are in close contact with the surface for more than 50% of the time and typically bound to the surface frequently through N-terminal ammonium groups, Lys side chains, and Arg side chains. To a lesser extent, polar residues with capability for hydrogen bonding such as Ser, Asp, and His contribute to peptide adsorption and cumulative effects between such residues appear essential. Meaningful simulations at the molecular level depend on justified models of the silica surface, the use of explicit water molecules at concentrations comparable to experiment, and force fields parameters for silica which reproduce experimentally determined surface and interface energies.
3:15 PM - NN6.3
Toward Simulations of Biological Polymorph Selection.
David Quigley 1 , Matt Bano 2 , Paolo Raiteri 3 , Julian Gale 3 , P. Mark Rodger 2
1 Department of Physics, University of Warwick, Coventry United Kingdom, 2 Department of Chemistry, University of Warwick, Coventry United Kingdom, 3 Nanochemistry Research Institute, Curtin University of Technology, Perth, Western Australia, Australia
Show AbstractThe processes by which organisms preferentially nucleate and grow metastable crystal polymorphs is still poorly understood. The role of molecular simulation in generating insight into these processes has yet to be fully realised, despite considerable recent progress in simulating orientational control [1] and enhancement of crystal stability [2] by organic molecules.In order to study thermodynamic polymorph control, one must perform simulations which sample from multiple phases accessible to a growing nucleus, and determine which is most probable under the applied conditions (e.g. presence of organic scaffolds or additives). Two fundamental limitations of molecular simulation must be addressed to achieve this. Firstly, models of ionic solids do not typically reproduce the relative thermodynamic stability of mineral polymorphs. This is largely due to difficulties in routinely computing free energy differences at high temperatures where quasi-harmonic approximations fail. To address this deficiency, we have adapted the lattice-switching Monte-Carlo method [3] to mineral systems, and used this to asses the efficacy of fitting models to enthalpy differences in reproducing relative free energies [4] leading to a much improved model for calcium carbonate. Secondly, sampling from the configurations available to a nucleus involves advanced sampling methods to overcome the fundamental timescale limitations of molecular dynamics. Approaches based on biasing of collective variables (CVs), such as metadynamics, have proved effective [5]. However these studies have required large numbers of CVs resulting in very costly calculations. Alternative CVs will be presented, including a promising approach based on the quantification of particle topology. The relative merits of these new CVs will be discussed, and simulations of polymorphic transitions in nanoparticles will be presented.Simulating kinetic control of polymorph selection presents further difficulties which will also be discussed.[1] D. Quigley, P. M. Rodger, C. L. Freeman, J. H. Harding and D. M. Duffy J. Chem. Phys., 2009, 131, 094703[2] C. L. Freeman, J. H. Harding, D. Quigley and P. M. Rodger Angew. Chem., 2010[3] A. D. Bruce, N. B Wilding and G. J. Ackland Phys. Rev. Lett., 1997, 79, 3002[4] P. Raiteri, J. D. Gale, D. Quigley and P. M. Rodger J. Phys. Chem. C., 2010, 114, 5997[5] D. Quigley and P. M. Rodger J. Chem. Phys., 2008, 128, 221101
3:30 PM - NN6.4
The Significance of Entropy for Molecular Binding at Mineral Surfaces.
Colin Freeman 1 , John Harding 1 , P. Rodger 2
1 Engineering Materials, University of Sheffield, Sheffield United Kingdom, 2 Chemistry, Warwick Univeristy, Coventry United Kingdom
Show AbstractThe binding of biomolecules to materials requires careful consideration of the complex interface [1]. There are the roles of different functional groups within the molecule, the surface chemistry and ordering of the ions within the material and in many cases the impact of water [2]. Analysing all these interactions involves both enthalpic and entropic changes that must be defined if a free energy of adsorption is to be calculated.Direct calculation of the entropic contribution with molecular dynamics is not possible since entropy is not an average property of the system. Extensions to the thermodynamic integration method have been suggested to extract the entropy from this free energy simulation [3].We examine the adsorption of several molecules onto calcite surfaces varying in size from a methanoic acid to the protein ovocledin-17. In each case we analyse the methods of binding and the effect on the molecule, surface and solvent. We conclude this analysis with estimates of the free energy of adsorption and the role of entropy in binding for the solvent and molecule.[1] Freeman C.L., Harding J.H., Quigley D.Q. Rodger P.M., Angew. Chem. Int. Ed., 49, (2010) [2] Freeman C.L., Asteriadis I., Yang M., Harding J.H., J. of Phys. Chem C , 113, (9), (2009), 3666[3] Smith D.E., Zhang L., Haymet A.D.J., J. Am. Chem. Soc. 114, (1992), 5875
4:15 PM - **NN6.5
Modulation of Crystal Growth by Mineralized-tissue Proteins.
Graeme Hunter 1 , Brian Chan 1 , Harvey Goldberg 1 , Bernd Grohe 1 , Susanna Hug 1 , Mikko Karttunen 1 , Gilles Lajoie 1 , Jason O'Young 1 , Kem Rogers 1
1 , University of Western Ontario, London, Ontario, Canada
Show AbstractProteins are known to control many aspects of biomineralization, including the nucleation, type, growth habit and orientation of crystals. We are studying two proteins that prevent the calcification of soft tissues, osteopontin (OPN) and matrix gla protein (MGP). In general, our approach is to synthesize peptides based on sequences in these proteins and use physical techniques (confocal microscopy, scanning electron microscopy, autototitration) and molecular dynamics (MD) simulations to study their interactions with the biominerals hydroxyapatite (HA) and calcium oxalate monohydrate (COM) (Grohe et al., J. Amer. Chem. Soc. 129, 14946, 2007; Azzopardi et al., PLoS One 5(2), e9330, 2010). Synthetic peptides OPN65-80 (pSHDHMDDDDDDDDDGD) and OPN220-235 (pSHEpSTEQSDAIDpSAEK) are potent inhibitors of HA growth in a constant-composition/seeded growth system. Both peptides preferentially adsorb to the {100} face of COM, which is the most basic face developed, inhibiting growth in the corresponding <100> direction. Less-acidic peptides do not adsorb to HA or COM, and do not affect crystal growth. To study the mechanism of face-specific adsorption, we created MD simulations of {121} steps on {100} and {010} faces of COM. Virtual peptide EEEEEEEEEEEEEEEE adsorbs to a {121} riser in preference to an {010} base, but adsorbs to a {100} base in preference to a {121} riser. MD was also used to study the interactions of 14-amino-acid peptides of MGP to the {100} face of HA. MGP1-14, which contains 3 phosphoserines and 1 γ-carboxyglutamic acid (gla), was predicted to adsorb rapidly to the {100} face. MGP29-42 and MGP43-56, which each contain 2 gla, adsorb more slowly, while the remaining (not post-translationally modified) peptides exhibit no interaction. Simulation of the adsorption of full-length MGP in its predicted tertiary structure shows a mode of interaction with the {100} face of HA involving both the phosphorylated N-terminus and the gla-rich helix. Based on these findings and related studies by others, we propose that the interaction between mineralized-tissue proteins and biological crystals has the following characteristics. Proteins containing clusters of high negative charge density, resulting from acidic amino acid content and/or post-translational modification, adsorb to Ca-rich crystal planes in a process that is primarily electrostatic rather than stereochemical in nature (Grohe et al., Langmuir 25, 11635-11646, 2009). These proteins inhibit biomineral growth by adsorbing to either base or riser of growth steps, depending on which lattice plane is more basic; thus, anionic proteins most effectively inhibit the growth of faces that are cationic or contain growth hillocks with cationic step risers. Supported by the Canadian Institutes of Health Research, the Natural Sciences and Engineering Research Council and the Shared Hierarchical Academic Computing Network.
4:45 PM - NN6.6
Probing the Local Environment of Magnesium in Apatites: A Combined Experimental-computation Study.
Danielle Laurencin 1 , Almora Barrios Neyvis 2 , Nora de Leeuw 2 , Christel Gervais Stary 3 , Christian Bonhomme 3 , Franck Fayon 4 , Steffen Kraemer 5 , Alan Wong 6 , Mark Smith 7
1 Institut Charles Gerhardt de Montpellier, UMR 5253, Universités de Montpellier 1 et 2 - ENSCM - CNRS, Montpellier France, 2 Department of Chemistry, University College London, London United Kingdom, 3 Laboratoire de Chimie de la Matière condensée de Paris, UMR 7574- Université Pierre et Marie Curie, Paris France, 4 CEMHTI (Conditions Extrêmes et Matériaux : Haute Température et Irradiation), UPR3079 CNRS, Orléans France, 5 LNCMI (Laboratoire National des Champs Magnétiques Intenses), UPR3228 CNRS, Grenoble France, 6 CEA Saclay, IRAMIS/SCM/LSDRM, Gif sur Yvette France, 7 Department of Physics, University of Warwick, Coventry United Kingdom
Show AbstractThe mineral phase of bone is mainly composed of a calcium phosphate called hydroxyapatite. Its composition differs from that of stoechiometric apatite, Ca10(PO4)6(OH)2, by the presence of different ionic substituents, both anions like (CO3)2-, and cations like Na+, Mg2+ and Sr2+… Each one of these ions plays an important role on the biological front, magnesium being for example capable of stimulating osteoblasts. Because of their biological importance, it is not surprising that these minority ions are present in materials elaborated for bone substitution, such as calcium phosphate based ceramics[1] and bioglasses.[2] However, the link between the structural role of these ions, in particular at the organic/inorganic interface, and their biological effect has seldom been established. This is particularly true in the case of cationic substituents, and it thus appears necessary to analyze and compare the local environment of minority cations in biomaterials and natural bone tissue, in order to help develop more efficient biomaterials.Recently, solid state NMR has started to emerge as one of the techniques of choice to describe the local environment around cations like Ca2+ and Na+ in both synthetic and natural apatites.[3-5] However, for trace elements like Mg2+, solid state NMR is more difficult to use, notably because magnesium-25 is a low-gamma isotope of low natural abundance. Here, we will show how the combination of high resolution 25Mg NMR experiments (performed at high magnetic fields - 14.1, 17.5, 19.6 and/or 30 T) and DFT calculations can shed light on the role of magnesium in synthetic apatites and biological tissues.--------------------------------------------------------------------------------References :[1] Gomes, S.; Renaudin, G.; Jallot, E.; Nedelec, J.-M. Appl. Mat. Interf. 2009, 1, 505.[2] Soulie, J.; Nedelec, J. M.; Jallot, E. Phys. Chem. Chem. Phys. 2009, 11, 10473 [3] Laurencin, D.; Wong, A.; Dupree, R.; Smith, M. E. Magn. Reson. Chem. 2008, 46, 347. [4] Laurencin, D.; Wong, A.; Dupree, R.; Hanna, J. V.; Smith, M. E. J. Am. Chem. Soc. 2008, 130, 2412.[5] Laurencin, D.; Wong, A.; Chrzanowski, W.; Knowles, J. C.; Qiu, D.; Pickup, D. M.; Newport, R. J.; Gan, Z.; Duer, M. J.; Smith, M. E. Phys. Chem. Chem. Phys., 2010, 12, 1081.
5:00 PM - NN6.7
Control of Adhesion of Amino Acids and Peptides to Metal Surfaces by Molecular Epitaxy and Induced Charges.
Hendrik Heinz 1 , Ras Pandey 2 , Rajiv Berry 3 , Joseph Slocik 3 , Barry Farmer 3 , Rajesh Naik 3
1 Department of Polymer Engineering, University of Akron, Akron, Ohio, United States, 2 Department of Physics, University of Southern Mississippi, Hattiesburg, Mississippi, United States, 3 Nanostructured and Biological Materials Branch, Air Force Research Laboratory, Wright-Patterson AFB, Ohio, United States
Show AbstractThis paper explains selective adsorption of amino acids on various metal surfaces such as {111}, {100}, and {110} of gold and palladium on the basis of advanced molecular simulation techniques under conditions close to experiment. The results are in agreement with a wide range of experimental data and suggest molecular epitaxy on the metal surfaces as a concept to tune the interaction of peptides versus solvent with metal surfaces by design. In essence, three factors determine the affinity of a biomolecule or of a surfactant to a metal surface in solution in the absence of covalent (non-thiol) bonding: (1) the surface energy of the metal, (2) the degree of time-averaged epitaxial fit of the solute to the surface in comparison to the solvent, (3) induced charges and entropy effects. The high surface energy of metals, which exceeds that of oxidic surfaces, leads to locally very deep wells in surface potential and thus promotes an epitaxial mechanism of adsorption of polarizable atoms (C, N, O) in organic molecules. Induced charges play a less important role, approximately 10-20% of epitaxial contributions on metal {111} surfaces. In absence of favorable epitaxy of peptides on metal {100} surfaces in aqueous solution, however, induced charges can play a dominant role to promote moderate adhesion with a partial water interlayer between the metal surfaces and charged peptides.Heinz et al. J. Am. Chem. Soc. 2009, 131, 9704.Heinz et al. J. R. Soc. Interface 2010 (in press).
5:15 PM - NN6.8
Hierarchical and Size Dependent Mechanical Properties of Silica Nanostructures Inspired by Diatom Algae.
Andre Garcia 1 2 , Dipanjan Sen 1 2 3 , Markus Buehler 1 2
1 Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Laboratory for Atomistic and Molecular Mechanics, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractBiology implements intriguing structural design principles that allow for attractive mechanical properties—such as high strength, toughness, and extensibility despite being made of weak and brittle constituents, as observed in biomineralized structures. For example, diatom algae contain nanoporous hierarchical silicified shells, called frustules, that provide mechanical protection from predators and virus penetration. These frustules generally have a morphology resembling honeycombs within honeycombs, meshes, or wavy shapes, and are surprisingly tough when compared to bulk silica, which is one of the most brittle materials known. However, the reason for the enhanced mechanical properties has remained elusive. Here we propose that one reason for the superior mechanical properties lies in the geometric arrangement, size, and shape of the silica structures. By carrying out a series of molecular dynamics simulations with the first principles based reactive force field ReaxFF, the mechanical response of the structures is elucidated and correlated with underlying deformation mechanisms. Specifically, it is shown that when concurrent mechanisms occur, such as shearing and crack arrest, toughness is optimally enhanced; and is observed with the hierarchical assembly of foil elements into a mesh structure, which could not be achieved in foil structures alone. For wavy silica, unfolding mechanisms are achieved for increasing amplitude, and allow for greater ductility of up to 270% strain. Furthermore, these deformation mechanisms are governed by the size and shape of the structure. Our results demonstrate that including higher levels of hierarchy are beneficial in improving the mechanical properties and deformability of intrinsically brittle materials. The findings reported here provide insight into general material design approaches that may enable us to transform a brittle material like silicon or silica into a ductile, yet strong and tough material, solely through alterations of its structural arrangement at the nanoscale, achieved through a merger of the concepts of structure and material.
Symposium Organizers
John Harding University of Sheffield
Sheng Lin-Gibson National Institute of Standards and Technology
John Spencer Evans New York University
Kiyotaka Shiba Japanese Foundation for Cancer Research
NN7: Applications - Medical Devices
Session Chairs
Thursday AM, December 02, 2010
Liberty B/C (Sheraton)
10:00 AM - NN7.1
Silk/Silica Biomaterials for Bone Tissue Regeneration.
Aneta Mieszawska 1 , David Kaplan 1 , Carole Perry 2 , Bruce Rutherford 3
1 Biomedical Engineering, Tufts University, Medford, Massachusetts, United States, 2 School of Biomedical and Natural Sciences, Nottingham Trent University, Nottingham United Kingdom, 3 Department of Oral Biology, University of Washington, Seattle, Washington, United States
Show AbstractSilk/silica chimeric proteins were studied as new biomimetic nanocomposites for bone repair and tissue engineering. Spider dragline silk consensus repeats represent a hydrophobic self assembling domain of a chimera that forms highly stable (beta-sheet) secondary structures with outstanding mechanical properties. The hydrophilic silica forming domain derived from the silicatein protein of a diatom offers fine control over silica formation for material mineralization. Recombinant DNA techniques were used to design protein fusions with control or tailored nanocomposite material features with tunable performance towards new bone formation. These fusion proteins provide an approach for nanoscale materials assembly leading to well-organized composite structures with control of organic-inorganic interfaces to optimize material features. The impact of modifications at the molecular level in the organic phase (silk repeats), as well as different chemistries in the silica precipitating domains (chemically designed peptides), were assessed for their influence on material properties such as morphology, structure, and mechanics of biomaterials formed from these proteins. The studies indicate successful formation of nanocomposites with useful mechanical properties, control of different silica morphologies, and biocompatibility. Outcomes were assessed by interactions of human mesenchymal stem cells (hMSC) with the bioengineered nanocomposites towards osteogenesis differentiation. For comparison, blended protein biomaterials of silk fibroin with different sized silica nanoparticles were also assessed in similar cell based assays.
10:15 AM - NN7.2
Construction of Nanostructured Hydroxyapatite-coated Genipin-chitosan Fluorescent Bone Scaffold and Differentiation of Rat Bone Marrow Stem Cell on It.
Hong Liu 1 , Guancong Wang 1 , Lin Zheng 2 , Hongshi Zhao 1 , Junying Miao 3
1 state Key Laboratory of Crystal Materials, Shandong University, Jinan, Shandong, China, 2 School of Medicine, Shandong University, Jinan, Shandong, China, 3 College of Life Science, Shandong University, Jinan, Shandong, China
Show Abstract The demands for various biomedical bone implants to repair bone defects caused by bone fractures, osteoarthritis, osteopoosis or bone cancers become urgent because of increase of the world’s population, number of vehicles and environmental pollution. However, conventional tissue replacements, such as autografts and allografts, could not meet the quantity or performance demand necessary for today’s patients. Tissue engineering opens a new door for solving the current implanting problem by designing and preparation of bone scaffold.Normally, bone tissue engineering scaffold is a porous structured polymer or protein/hydroxylapatite (HAp) composite. Chitosan, a degradable native macromolecular polymer, is one of the most important substances for construction of bone scaffold. However, glutaric dialdehyde, normally used for preparation of HAp/Chitosan bone scaffold as crosslinker, is of toxic, which probably caused problems when the implant is embeded in human body. An ideal scaffold, particular porous biodegradable polymer/hydroxyapatite composites, should posses hierarchical porous structures to achieve desired mechanical function and mass transport (permeability and diffusion) properties, have cell selective interface to conduct cell attachment and regulate cell functions, and allow facile image and tracking properties. In this study, to construct a hydroxyapatite (HAp) coated genipin-chitosan conjugation scaffold (HGCCS) with well-defined HAp nano-structured surface, we have developed a simple and controllable approach that allows construction of a 2-level 3-dimensional networked structure with fluorescent property and enhanced strength. Using a nontoxic cross-linker (genipin) and a nano-crystallon induced biomimetic mineralization method, we have assembled high-strength HAp nano-network structure on the chitosan framework. More importantly, herein we first study the fluorescent property and 3-dimensional microstructure of HGCCS by confocal laser scanning microscopy (CLSM). This fluorescent scaffold without toxicity also permits convenient investigation of biomaterial biodegradability and monitoring of bio-degradation processes. Furthermore, the result of rat bone marrow stem cells (BMSCs) proliferation shows that HGCCS has high biocompatibility. Excitingly, through SEM and CLSM studies, we found that the HAp nano-network and nanostructures on the surface of chitosan channel can influence the morphology, proliferation and cytoskeleton organization of rat BMSCs, which opens a new research avenue to control stem cell lineage commitment for bone tissue engineering. To explore the possibility of application of this materials as a bone tissue engineering scaffold, the effect of surface biomimetic apatite nanostructure of chitosan/nano-hydroxyapatite scaffold on protein adsorption and osteogenic differentiation of rat bone marrow stem cells was investigated.
10:30 AM - NN7.3
Biodegradable Hydrogel-based Composites.
Jijun Huang 1 , Qiang Fu 1 , Manuel Houmard 1 , Grace Lau 1 , Eduardo Saiz 2 , Antoni Tomsia 1
1 Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 2 Center for Advanced Structural Ceramics, Department of Materials, Imperial College London, London United Kingdom
Show AbstractHydrogel-based organic-inorganic materials are increasingly attracting interest as bone tissue scaffolds. These scaffolds should provide good cell adhesion, mineral binding, and mechanical properties matching surrounding tissues. There have been recent developments in the field showing that poly(2-hydroxyethyl methacrylate), pHEMA, based hydrogels and their composites with hydroxyapatite are promising biocompatible materials for bone fillers and to build tissue engineering scaffolds, particularly for applications under low- and medium-load bearing conditions. The hydrogel-based composites are easy to cut and machine and show a remarkable resistance to compression and cyclic loading, even when the concentration of hydroxyapatite approaches 80 wt%. However, pHEMA based hydrogels are not biodegradable, and thus have limited applications.We have recently initiated our research efforts to create biocompatible, biodegradable, pHEMA-based hydrogels and composites. Our goal is to build a new series of porous, three-dimensional scaffolds using these materials. We purposely design the hydrogels to enhance cell adhesion, mineral binding capability, and biodegradability. This was done by tuning their macromolecular chain structures to include specific co-monomers and a biodegradable crosslinker, N, O-dimethacryloyl hydroxylamine. After synthesizing a series of pHEMA type hydrogels that will exhibit different biodegradation rates, composites are prepared using different approaches, including pre-mixing with calcium phosphate powders, electrophoresis, or bio-inspired biomineralization. In this work, we will demonstrate how we tuned the macromolecular structures of hydrogels to achieve biodegradability. The static and dynamic mechanical properties of the materials are also analyzed and related to their composition and microstructure. The results are used to discuss the possible applications of this class of materials in bone repair. This work was supported by the National Institutes of Health/National Institute of Dental and Craniofacial Research (NIH/NIDCR) Grant No. 1 R01 DE015633.
10:45 AM - NN7.4
Robocasting of Bioactive Glass Scaffolds for Load-bearing Bone Regeneration
Qiang Fu 1 , Eduardo Saiz 2 , Antoni Tomsia 1
1 Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 2 Center for Advanced Structural Ceramics. Department of Materials, Imperial College of London, London United Kingdom
Show AbstractThe development of novel biodegradable scaffolds for the treatment of bone defects is the subject of intense research. A successful scaffold will guide cell-attachment, proliferation and tissue regeneration while maintaining adequate mechanical strength. Diverse techniques such as replica template, emulsion, freeze casting etc, have been used to build porous scaffolds. However, most of them offer only a very limited control of the porosity and are not suited to fabricate materials with complex shapes. Direct write assembly or robocasting is a computer guided micro-extrusion process that permits the printing of ceramic scaffolds with very complex geometries and architectures following a computer design and with spatial resolutions that can go down to submicron levels. Robocasting inks can be processed both from ceramic powders or sol-gel precursors and have to flow under stress and recover enough stiffness when the stress is released, bearing the weight of the printed part. Water-based inks are preferred as they are safer and the content of organics that should be burned out during sintering is much reduced.Bioactive glasses are a very attractive material to build tissue engineering scaffolds. Because the composition of the glass can be easily tuned they offer the possibility of formulating materials with different biodegradation rates tailored for specific applications. In addition, it has been proposed that the dissolution products of the glass may play an active role on osteoblast behavior. The use of computer-aided fabrication to build materials based on bioactive glasses is a challenging problem due to their reactivity, bioactive glass powders tend to be unstable in water-based inks. Here we used glasses in the SiO2-CaO-MgO-K2O-Na2O-P2O5 system to prepare bioactive glass scaffolds for potential use in load-bearing situations by robotic assisted deposition. The stability of these glasses combined with a careful control of the particle size distribution allows the formulation of ceramic inks using thermally reversible hydrogels. The inks can flow through nozzles as thin as 30 μm. The resulting glass scaffolds exhibit compressive strengths up to 136 MPa, comparable to cortical bone, and porosity of ~60%. In vitro evaluation of the scaffolds in simulated body fluid (SBF) indicated excellent bioactivity. The results demonstrate that bioactive glass scaffolds fabricated by the direct write assembly technique may serve as good candidate for the fabrication of structures to support repair and regeneration of load-bearing bone defects. This work was supported by the National Institute of Health (NIH/NIDCR) grant No. 1 R01 DE015633
11:00 AM - NN7: App
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11:30 AM - NN7.5
In Vitro Mineralization of Preosteoblasts in Poly (D, L-lactide-co-glycolide) Inverse Opal Scaffolds Reinforced with Hydroxyapatite Nanoparticles.
Sung-Wook Choi 1 , Yu Zhang 1 , Stavros Thomopoulos 2 , Younan Xia 1
1 Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri, United States, 2 Orthopaedic Surgery, School of Medicine, Washington University in St. Louis, St. Louis, Missouri, United States
Show AbstractInverse opal scaffolds made of poly(D, L-lactide-co-glycolide) (PLGA) and hydroxyapatite (HAp) were fabricated using cubic-closed packed (ccp) lattices of uniform gelatin microspheres as templates and evaluated for bone tissue engineering. The scaffolds exhibited a uniform pore size (213 ± 4.4 μm), a porosity of ~75%, and an excellent connectivity in three dimensions. Three different formulations were examined: pure PLGA, HAp-impregnated PLGA (PLGA/HAp), and apatite (Ap)-coated PLGA/HAp. After seeding with preosteoblasts (MC3T3-E1), the samples were cultured for different periods of time and then characterized by X-ray microcomputed tomography (micro-CT) and scanning electron microscopy (SEM) to evaluate osteo-inductivity in terms of the amount and spatial distribution of mineral secreted from the differentiated preosteoblasts. Our results indicate that preosteoblasts cultured in the Ap-coated PLGA/HAp scaffolds secreted the largest amount of mineral, which was also homogeneously distributed throughout the scaffolds. In contrast, the cells in the pure PLGA scaffolds secreted very little mineral that was mainly deposited around the perimeter of the scaffolds. These results suggest that the uniform pore structure and favorable surface properties could facilitate the uniform secretion of extracellular matrix from cells throughout the scaffold. The Ap-coated PLGA/HAp scaffolds with uniform pore structure could be a promising material for bone tissue engineering.
11:45 AM - NN7.6
Fist Principles Study of Hydroxyapatite (HA) Surfaces and Ti(O2)/HA Interfaces.
Alexander Slepko 1 , Alexander Demkov 1
1 Physics, The University of Texas at Austin, Austin, Texas, United States
Show AbstractA carbonated form of hydroxyapatite (HA) [Ca10(PO4)6(OH)2] is one of the most abundant materials in mammal bone. It crystallizes within the spaces between tropocollagen protein chains and strengthens the bone tissue. The mineral content of a typical human bone increases with age and reaches a maximum value in males and females at different ages. From this peak value the mineral content starts to decrease leading to diseases such as osteomalacia (loss of bone mineral). An emergent application of HA is, therefore, bone repair and replacement. Although HA is bioactive it is a brittle material and by itself does not meet the requirements of a suitable bone replacement. Therefore, Ti and its alloys were primary candidates for implants for several decades combining high mechanical strength and biocompatibility. However, recently new approaches were sought to initiate a faster biological response, improve adhesion between the bone and the implant, provide a scaffold for bone growth and support the bone healing process by guiding bone tissue over the implant’s surface (osteoconduction). To meet these demands coating techniques were developed to cover the metallic implants in thin layers of HA. Such bioactive implants allow newly formed bone tissue to grow into any surface irregularities. Theoretically, little is known about HA/Ti and HA/TiO2 interfaces and experimental investigation is difficult. Using density functional theory, we analyze the electronic properties, surface energetics and reactivity of HA for different orientations and terminations using the frontier orbital approach. Using HA slabs with highly reactive surfaces we build atomistic models of Ti/HA and TiO2/HA interfaces. We study the effect of interface stoichiometry on adhesion properties between Ti and TiO2 on one side and HA on the other side and analyze the influence of adding Si on the adhesion of HA to Ti and TiO2.
12:00 PM - NN7.7
A Novel Concept for Optimizing Surface Topographical for Bone Implant.
Gillian Munir 1 , Xiang Li 1 , Lucy Di Silvio 2 , William Bonfield 3 , Mohan Edirisinghe 1 , Jie Huang 1
1 Department of Mechanical Engineering, University College London, London United Kingdom, 2 Biomaterials, Biomimetics and Biophotonics, King's College Dental Institute, London United Kingdom, 3 Department of Materials Science and Metallurgy, University of Cambridge, Cambridge United Kingdom
Show AbstractMetal implants have been used to serve mankind for over a century. Due to the inherent properties of metal, they can never mimic natural bone, however studies have shown altering surface chemistry and topography positively impacts cellular response and therefore increasing the life time of the implant. Thus, the concept of a novel nano-sized silicon-substitute hydroxyapatite (nanoSiHA) coated implant material with 3-D surface topographies, able to guide bone tissue remodeling, has become attractive. However, the processing techniques for such materials are still lacking. Recently, a reported novel technique, template-assisted electrohydrodynamic atomization (TAEA) spraying, is of considerable interest. The TAEA process evolves from electrohydrodynamic atomization spraying,, an electric-drive jet-based deposition method and inherits a range of advantages, such as ambient processing, low-cost and easy-setup. In this study, a more systematic approach has been employed to control the patterns produced by TAEA and the subsequent cellular response from the pattern. Nano-sized SiHA suspension (3%wt) was used as the raw material with commercial pure Ti as the substrate. The TAEA process setup is shown in Figure 1a. NanoSiHA suspension was syringed to the needle at a flow rate of 4µl/min, and a cone-jet patterning mode achieved with the applied voltage between the needle and the ground electrode set at 4.5-5.5kV. Copper templates with different shape and dimensions were placed on the surface of Ti. The patterned Ti samples were heat-treated at 600°C. The biological responses of human osteoblast (HOB) cells to linear track and pillar nanoSiHA patterned Ti was investigated. The attachment and orientation of HOB cells on nanoSiHA coated Ti were examined using SEM and confocal microscopy. NanoSiHA particles were distributed, forming a uniform and ordered topography on the Ti surface. The spaces between the islands were kept constant and varied only by a few micrometers, and by using the same template, the shape and size of islands in the entire coating was consistent.HOB cells attach to the nanoSiHA distributed in the line patterns, and thus are effectively guided by linear nHA patterns on Ti substrate as shown the SEM and confocal microscopy images. We systematically elucidated a new method for the creation of nanoSiHA deposition with abundant defined micro-scale surface topography with bioactive material. The in-vitro study demonstrated that cell response can be effectively controlled and orientated on this novel implant materials surface. This is a significant step forward in the new generational implant research for engineering bone remodeling.
12:15 PM - NN7.8
Induction of Dental Pulp Stem Cell Differentiation by Polymeric Substrates.
Aneel Bherwani 1 , Chung-Cheh Chang 2 , Aaron Akhavan 3 , Joseph Spiegel 3 , Vladimir Jurukovski 2 4 , Elaine DiMasi 5 , Miriam Rafailovich 2 , Marcia Simon 1
1 Oral Biology and Pathology, Stony Brook University, Stony Brook, New York, United States, 2 Materials Science, Stony Brook University, Stony Brook, New York, United States, 3 , Ramban Mesizta High School, Cedarhurst, New York, United States, 4 Biology, Suffolk Community College, Selden, New York, United States, 5 National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York, United States
Show AbstractIn-vitro, dental pulp stem cells (DPSC) can undergo odontoblast, osteoblast, neuronal and adipogenic differentiation dependent upon substrate and soluble mediators. We have previously shown that substrate mechanics plays a role in DPSC differentiation on elastomeric substrates. In the current study we evaluated the impact of a rigid but biocompatible polymer, polymethylmethacrylate (PMMA) and additionally compared film morphology. The following substrates were prepared: [1] 200 nm films spun cast on HFX-Si wafers, annealed for 24-hours at 170oC under a vacuum of 10-4 Torr, [2] 5 µm electrospun PMMA onto 200 nm films, annealed for an additional 30-minutes to secure the fiber onto the PMMA surface and [3] 10 µm electrospun PMMA onto 200 nm PMMA surface and re-annealed. DPSC were obtained from pulp tissues of extracted wisdom teeth under protocols approved by the Stony Brook University Internal Review Board. Primary cells were isolated by enzymatic digestion and used from 3rd-5th passage. For experiments on differentiation, cultures were grown in alpha-MEM supplemented with 10% fetal bovine serum, 0.2 mM L-ascorbic acid 2-phosphate, 2 mm glutamine, 10 mM beta-glycerol phosphate either with or without 10 nM dexamethasone. After 21-days samples were examined using confocal microscopy of cells stained with Alexafluor 488-linked phalloidin and propidium iodide, and by scanning electron microscopy (SEM) and Energy dispersive X-ray Analysis (EDAX). No significant differences in actin filament organization were observed for cells grown on PMMA with or without dexamethasone. Odontoblast and osteoblast markers are being evaluated by RT-PCR. DPSC were found to biomineralize on PMMA in the absence of dexamethasone. Data from SEM-EDAX showed formation of mineralized matrix comprising calcium, phosphorous, oxygen and carbon. The effect of morphology will be discussed.
12:30 PM - NN7.9
Moderate-intensity Static Magnetic Field Promotes the Biomineralization of Osteoblast-like Cells.
Xiaolan Ba 1 , Yizhi Meng 1 , Elaine DiMasi 2 , Miriam Rafailovich 1
1 Materials Science and Engineering, Stony Brook University, Stony Brook, New York, United States, 2 National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York, United States
Show AbstractMagnets have been clinically used as an “induction source” in various bone or orthodontic treatments. However, the mechanism and effects of magnetic fields remain unclear. We undertook the present investigation to study the effects of static magnetic fields (SMF) on extracellular matrix (ECM) development and cell biomineralization on negatively charged polymers. In this in vitro study, MC3T3-E1 osteoblast-like cells were exposed to 150 mT SMF in a vertical direction to the dish for up to 28 days. The effects of SMF on cell morphology, proliferation and orientation were characterized by confocal laser scanning microscopy (CSLM). To monitor the subtle changes of cells and ECM protein fibers during the initial stage of biomineralization, atomic force microscopy (AFM) and shear modulation force microscopy (SMFM) were used to characterize the morphology and mechanical property. The late-stage of mineralization was characterized by scanning electron microscopy (SEM) and grazing incident X-ray diffraction (GIXD). The data, thus far, shows that in the presence of the SMF the modulii of the osteoblasts is higher, than the modulii of cells not exposed to the SMF. GIXD indicates that more biomineralized produces are produced in the culture exposed to SMF. These results are consistent with proposed SMF therapies for bone healing. Results from other protein assays correlated to the biomineralization sequence will be presented in order to try to understand the underlying mechanism.