Jinwoo Cheon Yonsei University
Hedi Mattoussi Naval Research Laboratory
Christof M. Niemeyer Universitaet Dortmund
Geoffrey Strouse Florida State University
PP1: Synthesis, Functionalization and Bio-interfacing of QDs and Nanoparticles
Monday PM, November 26, 2007
Room 203 (Hynes)
9:30 AM - **PP1.1
Nanocrystal Quantum Dots for Biomedical and Biological Imaging.
Moungi Bawendi 1 Show Abstract
1 Department of Chemistry, MIT, Cambridge, Massachusetts, United States
This talk will review background chemistry and photophysics of nanocrystal quantum dots that is relevant to their application in biological and biomedical imaging. We will discuss control of hydrodynamic size, valency, and non-specific binding. Valency, or the number of binding sites per quantum dots, is an important parameter to control. Some applications take advantage of the potential high valency to insure sensitive detection, others require a single binding site per quantum dot, such as for tracking single receptors on the surface of living cells. We will give an example of an in vitro application where one quantum dot is conjugated to a single genetically engineered monomeric streptavidin, to provide a single binding site to biotin for each quantum dot. The issue of overall size of the quantum dot is important for both in vitro and in vivo imaging. For some experiments a hydrodynamic diameter of ~15nm to ~30nm is quite appropriate, but for efficient diffusion into tissue and for renal clearance a smaller hydrodynamic diameter is desired. We will provide specific examples of tuning size and surface characteristic, and showing renal clearance of properly designed quantum dots. We will show that quantum dots can be engineered to be more than passive reporters of their location; that they can also act as sensors of their microenvironment. We will provide an example of a quantum dot based pH sensor that is ratiometric and self-referencing and that is optimized for the biological environment.
10:00 AM - PP1.2
Semiconductor-magnetic Dimers: Synthesis and Comparative Characterisation.
Marco Zanella 1 5 , Andrea Falqui 3 2 , Stefan Kudera 1 4 5 , Liberato Manna 4 , Maria Casula 2 , Wolfgang Parak 1 5 Show Abstract
1 Physik, Philipps-Universität Marburg, Marburg Germany, 5 Biophysik, LMU, Muenchen Germany, 3 Departement de Genie Physique, Institut National de Sciences Appliqueés, Toulouse France, 2 Scienze Chimiche, Università di Cagliari, Cagliari Italy, 4 , CNR-INFM-NNL Distretto Tecnologico – ISUFI, Lecce Italy
10:15 AM - PP1.3
Stability of Vesicles Interacting with Functionalized Water-soluble CdSe/ZnS Quantum Dots: Effect of the Charge, Size and Chemical Coating.
Aurelien Dif 1 , Michele Baudy-Floch 1 , Etienne Henri 2 , Franck Artzner 2 , Maxime Dahan 3 , Valerie Marchi-Artzner 1 Show Abstract
1 Chemistry Department, University of rennes 1, Centre national de la Recherche Scientifique, C.N.R.S. UMR 6226, Rennes France, 2 Physik department, University of rennes 1, Centre national de la Recherche Scientifique, C.N.R.S. UMR 6626, Rennes France, 3 Physik department, Ecole Normale Supérieure, Centre national de la Recherche Scientifique, C.N.R.S. , Paris France
10:30 AM - PP1.4
DNA-templated Inorganic Nanoparticles: Synthesis, Properties, and Potential Applications.
Jong Hyun Choi 1 , Kok Hao Chen 1 , Michael Strano 1 Show Abstract
1 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Semiconductor and magnetic nanoparticles have unique optical and magnetic properties due to quantum confinement effects, and a variety of promising approaches have been devised to interface the nanomaterials with biomolecules for bioimaging and drug delivery applications. We present a novel scheme of synthesizing fluorescent and magnetic nanoparticles (NPs) using DNA oligonucleotides with various sequences. The quantum yield of fluorescence NPs depends on the DNA sequence used. The bonding chemistry between DNA and NP is studied using FTIR, suggesting that the carbonyl group of DNA base passivates the NP surface. The secondary structure of DNA is also involves in stabilizing the nanocrystals. Strong coordination of DNA on NPs provides the chemical stability, leading to high quantum yields. In vitro cytotoxicity of DNA-templated NPs is investigated with mouse fibroblast cells using hemacytometry and MTT assay, and the QDs are found to be non-toxic under the experimental conditions. Anti-cancer aptamer functionalized NPs are proposed as proliferation inhibitors, and their efficacy is examined with human breast cancer cells. The new synthesis scheme devised in this work should be valuable in designing and constructing a multifunctional drug delivery and imaging agent for biological systems.
10:45 AM - PP1.5
CdxZn(1-x)S:Mn/ZnS Alloy Semiconductor Core-shell Multimodal Qdots.
Soumitra Kar 1 , Swadeshmukul Santra 1 Show Abstract
1 NanoScience Technology Center and Department of Chemistry, University of Central Florida, Orlando, Florida, United States
Fluorescent quantum dots (Qdots) have demonstrated their potential in diagnostic bioimaging applications in vitro1. For in vivo bioimaging applications, however, the embodiment of additional properties such as paramagnetism into the same fluorescent probe is highly desirable. These multimodal probes would benefit in vivo disease diagnosis and surgical guidance based on their ability to be detected in multiple modes (i.e. optically and magnetically). Thus synthesis of bright multimodal Qdots is a mater of great interest to a broad area of scientific community from Physics to Bioscience. Owing to their wide band gaps, the II-VI group semiconductors such as CdS and ZnS served as good host materials for various kinds of foreign elements as dopant. Out of the different transition metals, manganese usually occupies substitutional sites in the (Cd or Zn) lattice as a divalent ion. The excitation and decay of manganese ion produces an yellow/orange luminescence at approximately 590 nm.2,3 This emission peak is generally associated with a transition between 4T1 and 6A1 energy levels. Also, the presence of the Mn2+ ions within the host Qdots introduces the paramagnetic property. Recently we have developed bright yellow-emitting CdS:Mn/ZnS core-shell Qdots4,5 with absorption maxima at 355 nm. This excitation wavelength is in the UV range, limiting their wide application in cellular imaging. In the present study, we have developed core-shell alloy semiconductor with CdxZn(1-x)S core and ZnS shell. This design allowed fine tuning of excitation band-gap, covering a wide range (from 2.4 eV to ~4 eV). When doped with Mn, these alloy Qdots emit bright yellow/orange light. In this presentation, we will describe successful fabrication of CdxZn(1-x)S:Mn/ZnS alloy semiconductor core-shell Qdots using a water-in-oil microemulsion technique. References:(1)Yang, H.; Santra, S.; Walter, G. A.; Holloway P. H., Adv. Mater., 2006, 18,2890.(2)Bhargava, R.N.; Gallagher, D.; Hong, X.; Nurmikko, A., Phys. Rev. Lett. 1994, 72, 416.(3)Biswas, S; Kar, S; Chaudhuri, S. Journal of Physical Chemistry B, 2005, 109 17526.(4)Yang, H.; Holloway P. H. Appl. Phys. Lett., 2003, 82, 1965.(5)Santra, S.; Yang, H.; Holloway P. H.; Stanley, J. T.; Mericle, R. A., J. Am. Chem. Soc. 2005, 127, 1656
11:30 AM - **PP1.6
Interfacing Cells with Colloidal Nanoparticles.
Wolfgang Parak 1 Show Abstract
1 Faculty of Physics, Philipps Universitaet Marburg, Marburg Germany
Two ideas for applications in which colloidal nanoparticles are used to interface cells will be discussed. Colloidal nanoparticles and in particular their surface chemistry will be discussed. A nanoparticles based FRET system for the detection of intracellular ions will be reported. An alternative system for the detection of intracellular ions based on polymer capsules / nanoparticles based will be describedInorganic hydrophobic nanoparticles of different materials can be transferred into aqueous solution by coating them with an amphiphilic polymer. Functional groups can be directly introduced in the polymer by reacting them to the backbone. This offers a very general route to water-soluble nanoparticles of high colloidal stability, with good size distribution, and with a variety of functional groups that are directly embedded in the polymer shell without the need of post-bioconjugation.Reference: C.-A. J. Lin, R. A. Sperling, J. K. Li, T.-Y. Yang, P.-Y. Li, M. Zanella, W. H. Chang, W. J. Parak, "Design of an amphiphilic polymer for nanoparticle coating and functionalization", submitted to SMALL.A FRET-pair based on colloidal quantum-dot donors and multiple organic fluorophores as acceptors is reported. In contrast to similar systems which are used as biosensors and detect specific changes of the donor/acceptor-distance under the influence of analyte binding, our nanoparticle design seeks to optimize sensors that detect spectral changes of the acceptor at fixed donor/acceptor distance. This approach allows for relatively small acceptor-donor distances, and thus for high energy transfer efficiencies, while simultaneously permitting high colloidal stability.Reference: M. T. Fernández-Argüelles, A. Yakovlev, R. A. Sperling, C. Luccardini, S. Gaillard, A. Sanz Medel, J.-M. Mallet, J.-C. Brochon, A. Feltz, M. Oheim, and W. J. Parak,"Synthesis and characterization of polymer-coated quantum dots with integrated acceptor dyes as FRET-based nanoprobes", submitted to NanoLetters.Polyelectrolyte microcapsules have been loaded with a pH sensitive, high molecular weight SNARF-1-dextran conjugate. SNARF-1 exhibits a significant pH-dependent emission shift from green to red fluorescence under acidic and basic conditions, respectively. The spectral properties of the dye were found to be largely retained after the encapsulation. Upon ingestion of SNARF-1-filled capsules by breast cancer cells or fibroblasts, the pH change of the local capsule environment during transition from the alkaline cell medium to the acidic endosomal/lysosomal compartments could be observed. By incorporating magnetic and fluorescent colloidal nanoparticles into the capsule-shell a novel type of multiplexed sensor system was developed.Reference: O. Kreft, A. Muñoz Javier, G. B. Sukhorukov, and W. J. Parak, "Microencapsulated Ion-Sensor as Novel Tool for In-Situ pH-Measurements", submitted to Chemistry of Materials.
12:00 PM - PP1.7
Biocompatible Quantum Dots Capped With Compact Multifunctional Ligands.
Kimihiro Susumu 1 , Igor Medintz 2 , Thomas Pons 1 , Hedi Mattoussi 1 Show Abstract
1 Optical Sciences Division, Code 5611, Naval Research Laboratory, Washington, District of Columbia, United States, 2 Center for Bio/Molecular Science and Engineering, U.S. Naval Research Laboratory, Washington, District of Columbia, United States
Semiconductor nanocrystals (quantum dots, QDs) offer several advantages for use in biological assay design and imaging. Their successful integration in biotechnology necessitates the preparation of water-soluble QDs that are highly luminescent, stable over a broad range of biological conditions and compatible with simple conjugation techniques. We have previously utilized readily available thioctic acid and poly(ethylene glycol)s (PEG) in simple esterification schemes, followed by reduction of the 1,2-dithiolane to prepare PEG-terminated dihydrolipoic acid (DHLA-PEG) capping substrates. Recently we further developed this scheme to prepare a series of DHLA-PEG ligands having a variety of functional end groups, including biotin and carboxyl groups. DHLA-PEG-biotin for example was prepared by coupling thioctic acid and biotin to the ends of amine-functionalized poly(ethylene glycol) followed by reduction of the 1,2-dithiolane group. Biotin permits the use of the ubiquitous avidin-biotin binding, whereas carboxyl groups allow the use of covalent reaction schemes to attach a variety of bioreceptors to QDs. All ligands are modular and each has a multidentate terminal group for strong anchoring on the QD surface, a PEG segment to promote hydrophilicity and a terminal group for biological linkage.Water-soluble QDs capped with one type or mixtures of the functional ligands were prepared via cap exchange with the native capping ligands. Homogeneous QD dispersions that are stable over extended periods of time and over broad pH range were prepared. Surface binding assay showed that DHLA-PEG-biotin-functionalized QDs strongly interact with NeutrAvidin-modified surfaces. The ability of the QDs functionalized with a mixed DHLA-PEG600:DHLA-PEG400-Biotin ligands to mediate cellular uptake and delivery of specific protein-attached cargoes was also investigated. EDC coupling in aqueous buffer solution was also demonstrated with DHLA–PEG–COOH-functionalized QDs and an amine-terminated energy transfer acceptor dye. We will present and discuss the synthetic routes employed and characterization of the materials prepared using NMR and IR spectroscopy. We will also describe the use of QDs capped with these ligands to design biologically functional assays.
12:15 PM - PP1.8
Silica-Coated Quantum Dots with a Paramagnetic and Pegylated Lipidic Coating as Target-Specific Nanoparticles for Multimodality Imaging Applications.
Rolf Koole 1 , Matti van Schooneveld 1 , Karolien Castermans 1 , Jan Hilhorst 2 , Celso de Mello Donega 1 , Daniel Vanmaekelbergh 1 , Arjan Griffioen 2 , Klaas Nicolay 3 , Zahi Fayad 4 , Andries Meijerink 1 , Willem Mulder 4 Show Abstract
1 Condensed Matter & Interfaces, Debye Institute, Utrecht University, Utrecht Netherlands, 2 , Maastricht University and Hospital, Maastricht Netherlands, 3 , Eindhoven University of Technology, Eindhoven Netherlands, 4 , Mount Sinai School of Medicine, New York, New York, United States
A large variety of nanoparticle contrast agents are currently developed to contribute to the field of bio-imaging. The possibility to incorporate/include multiple functionalities for different imaging techniques, and the high payload of contrast generating material per particle are important advantages compared to conventional contrast agents. Furthermore, the surface of nanoparticles can be easily modified to improve bio-compatibility or to attach multiple targeting ligands per nanocrystal. Quantum Dots (QDs) are promising candidates for bio-imaging because of their unique and stable optical properties. Recently, we showed that QDs could be used for multi-modality imaging, by coating the QDs with paramagnetic lipids (for MRI detection). In addition we have shown that they can be targeted to apoptotic and angiogenic cells via the conjugation of suitable ligands.[1,2] However, the cytotoxicity of Cadmium-containing QDs is still an important drawback for bio-applications. To circumvent this problem, we have incorporated the QDs in silica spheres by the reversed micro-emulsion method. In this study we also established the incorporation mechanism of QDs in silica. This enabled us to synthesize highly monodisperse silica particles (Ø 35 ± 2nm) with a single QD incorporated exactly in the centre, while retaining a high quantum efficiency (QE) >35%.The QD/silica particles were coated by hydrophobic ligands, allowing the transfer of these particles into the hydrophobic core of lipidic micelles in water. The lipidic coating consisted of paramagnetic amphiphiles (Gd-DTPA-BSA) and pegylated lipids (PEG-DSPE). The paramagnetic lipids enable the detection with MRI, whereas the pegylated lipids improve the bio-compatibility and circulation half-life of the nanoparticle. In addition, a fraction of maleimide functionalized PEG-DSPE lipids was included to enable the attachment of specific targeting ligands. In this study, we conjugated αvβ3-specific RGD-peptides to the maleimide groups, and found a high specific up-take of the QD/silica/Lipid/RGD-particles by human endothelial cells (HUVEC) in vitro. Untargeted particles did marginally associate with these cells. Due to the high surface area of the silica spheres, about 300 RGD-peptides and 3500 Gd-moieties per particle could be realized. The longitudinal relaxivity (r1) per particle was determined to be 50750 mM-1s-1.The presently reported contrast agent consists of an efficient and stable fluorescent nanoparticle surrounded by a high payload of paramagnetic lipids and targeting ligands, and therefore meets all requirements for target-specific multimodality imaging.Mulder, W. J. M.; Koole, R.; Brandwijk, R. J.; Storm, G.; Chin, P. T. K.; Strijkers, G. J.; deMelloDonega, C.; Nicolay, K.; Griffioen, A. W. Nano Lett. 2006, 6, 1.van Tilborg, G. A. F.; Mulder, W. J. M.; Chin, P. T. K.; Storm, G.; Reutelingsperger, C. P.; Nicolay, K.; Strijkers, G. J. Bioconjugate Chemistry 2006, 17, 865.
12:30 PM - PP1.9
An Expanded Color Palette of Qdot® Nanocrystal Bioconjugates for Use in a Diverse Range of Biological Applications.
John Mauro 1 , Shulamit Jaron 1 , Jason Kilgore 1 , Julie Nyhus 1 , Thomas Steinberg 1 , Yu-Zhong Zhang 1 Show Abstract
1 Biosciences, Invitrogen Corporation, Eugene, Oregon, United States
Applications of semiconductor nanocrystal bioconjugates in studying biological systems include multi-target cell and tissue immunolabeling and microscopic imaging, high sensitivity flow cytometric biomarker detection and immunophenotyping, quantitative multicolor Western blotting and small animal in vivo imaging. An expanded set of uniquely photostable Qdot nanocrystal bioconjugates has been developed and is commercially available for use across a broad range of the visible and near-infrared spectrum (525, 545, 565, 585, 605, 625, 655, 705 and 800 nm-centered emission). The latest additions to this reagent set are 625 nm emitting Qdot streptavidin, goat anti-mouse and goat anti-rabbit antibody conjugates. The Qdot 625 bioconjugates are derived from nanocrystals which are among the brightest fluors ever created, with extremely high light absorbance (molar extinction coefficient at 405 nm of ~14,000,000 M-1cm-1) and near optimal quantum yield (average QY of 90%). In cell and tissue imaging, upon excitation of all nanocrystal bioconjugate colors simultaneously present with near UV or blue light, appropriate spectral deconvolution yields photomicrographs with six or more spatially resolved subcellular zones and structures. In flow cytometry, bright nanocrystal bioconjugates can replace standard dye-based tandem conjugates in multiplexed applications requiring large effective Stokes shifts. Nanocrystal-probed Western blots can reduce the need for use of multiple blots by providing more information using a single multicolor blot. Injected nanocrystals have unique distribution patterns in mice that may be useful for investigating normal and diseased animals by non-invasive imaging. We present examples of use of Qdot nanocrystals and their conjugates in each of these areas.
12:45 PM - PP1.10
Multifunctional Nanoparticles with Paramagnetic and NIR Absorption Properties.
Yongdong Jin 1 , Jingwei Bai 1 , Yu Huang 1 Show Abstract
1 Materials Science and Engineering, UCLA, Los Angeles, California, United States
Over the past decade, magnetic nanoparticles (NPs) have been actively pursued for potential biomedical applications such as magnetic resonance imaging (MRI), hyperthermia agents and targeted drug delivery. In general, magnetic NPs require shell coatings to achieve structure stability, good biocompatibility and the ability of further surface functionalizations. Magnetic-core Au-nanoshell NPs have captured particular attention, due to the combined functions of magnetic and optical properties from both components, which can lead to exciting opportunities for integrated imaging, diagnosis, targeted drug delivery and therapeutics. Au nanoshells have unique near infrared (NIR) plasmon resonance and hence NIR optical absorption, which makes them ideally suited for a variety of biomedical applications, such as photo-thermal cancer therapy4 and whole-blood immunoassays.9 Furthermore, thiol chemistry has been well established for introducing versatile surface functions to Au NP surfaces. However, synthesizing magnetic-core/Au-shell NPs and simultaneously retaining the properties of both components has remained a challenge. In this talk we demonstrate the synthesis of Fe2O3/protein/Au core/shell/shell multifunctional NPs with preserved paramagnetic property and tunable NIR absorption using apoferritin protein cage as biological templates. Biomimetic mineralization produces iron oxide cores with diameters around 8 nm. The formation and NIR absorption of Au nanoshells on the template surface was confirmed by TEM, SAED and optical absorption studies. SQUID magnetometry demonstrated that the iron oxide cores are paramagnetic, and that their magnetic property is retained after coating Au nanoshells. In this structure, the ferritin protein cage functions as a dielectric layer to separate the magnetic core from the Au shell and plays an important role in simultaneously preserving the paramagnetic property of the iron oxide core and the NIR absorption property of the Au nanoshell.
PP2: Interfacing QDs with Bioreceptors, Cells and Redox Complexes
Monday PM, November 26, 2007
Room 203 (Hynes)
2:30 PM - **PP2.1
Electron and Energy Transfer Mechanisms to Switch the Luminescence of Semiconductor Quantum Dots.
Francisco Raymo 1 Show Abstract
1 Chemistry, University of Miami, Coral Gables, Florida, United States
The goal of our research program is the development of luminescent chemosensors based on the unique photophysical properties of semiconductor quantum dots. In this context, we have designed viable strategies to switch the luminescence of CdSe-ZnS core-shell quantum dots in response to target analytes. Our protocols are based on the exchange of either electrons or energy between these inorganic nanoparticles and appropriate organic ligands upon excitation. We have demonstrated that these processes can be exploited to probe pH and protein–ligand interactions. Thus, our fundamental studies can lead to valuable analytical tools for biomedical applications, while contributing to advance the basic understanding of the properties of semiconductor quantum dots.
3:00 PM - PP2.2
Redox Control of Quantum Dot-Bioconjugate Photoluminescence.
Igor Medintz 1 , Thomas Pons 2 , Scott Trammell 1 , Florence Brunel 3 , Philip Dawson 3 , Hedi Mattoussi 2 Show Abstract
1 Center for Bio/Molecular Science and Engineering, U.S. Naval Research Laboratory, Washington, District of Columbia, United States, 2 Division of Optical Sciences , U.S. Naval Research Laboratory, Washington, District of Columbia, United States, 3 Department of Cell Biology and the Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla , California, United States
Colloidal QDs have a large fraction of their atoms arrayed on their surfaces and they are always capped with bifunctional ligands. These ligands along with the surrounding matrix affect the overall photophycial properties of the nanocrystals, due the presence of defect surface states often attributed to dangling bonds and incomplete surface passivation. These nanocrystals are thus sensitive to the presence of additional charges (electrons or holes) in close proximity to the surface, which can alter both photoluminescence and absorption spectra. This has stimulated interest in creating hybrid bio-devices based on potential reversible charge-transfer between a QD and proximal redox active bioreceptors. In order to understand the underlying mechanisms in a controlled manner, we labeled a series of peptides with specific redox-active groups, ratiometrically self-assembled them onto the surface of hydrophilic QDs, and tested their ability to influence the nanocrystal spectroscopic properties, using cyclic voltametry, absorption, steady-state and time-resolved fluorescence. Our results revealed that the presence of proximal redox groups do alter the optical properties of the nanocrystals. In particular we found that PL quenching was pronounced with a clear dependence on the ratio of peptide-to-QD used, only when groups that have favorable redox levels were used. The information we gained from the above experiments was further used to develop sensors specific for the detection of particular enzymes using peptides expressing a specific peptidase-recognized sequences. We will discuss the data within the framework of charge transfer from the redox group to either surface or core states in the QDs. Additional aspects such as type of QD surface-capping used (neutral versus chargeable), core size will also be discussed.
3:15 PM - PP2.3
Exciton-plasmon Interaction in Bio-conjugated Nanocrystals as Sensor Mechanism.
Alexander Govorov 1 , Pedro Hernandez 1 , Jaebeom Lee 2 , Nicholas Kotov 2 Show Abstract
1 , Ohio University, Athens, Ohio, United States, 2 , University of Michigan, Ann Arbor, Michigan, United States
Motivated by recent experiments on nanocrystal superstructures [1,2], we develop theoretical models of sensors based on the interacting metal and semiconductor nanocrystals. In bio-conjugated structures, a sensor mechanism comes from the exciton-plasmon interaction and from special bio-linkers between plasmonic element (gold or silver nanoparticle) and quantum emitter (CdTe nanoparticle or nanowire). The linkers can be sensitive to temperature  or to chemicals  . In the nano-thermometer realized experimentally in ref. , the polymer linker undergoes phase transition with increasing the temperature. Therefore, the spatial separation between metal and semiconductor nanocrystals varies with temperature resulting in variation of emission. In a sensor of proteins , the distance between nanowire and gold nanoparticles depends on the presence of certain molecules (proteins) in a solution. As a result of distance variation, the exciton emission energy becomes sensitive to a protein concentration. We explain the exciton shift in terms of exciton diffusion along the nanowire and exciton energy transfer from nanowire to metal nanoparticles. A theory based on the diffusion and rate equations describes well the experimental data. The rates of energy transfer are calculated using the fluctuation-dissipation theorem. In addition, exciton-plasmon interaction can be tailored by choosing the material system and geometry. For example, it is possible to realize the regimes of strong photon-plasmon and exciton-plasmon interactions. The first occurs in silver-CdTe structures and the second in gold-CdTe complexes. Our study shows that the nano-assemblies with the exciton-plasmon interaction can be used as temperature- and bio- sensors.  J. Lee, A. O. Govorov, and N. A. Kotov, Angewandte Chemie, 117, 7605 (2005) J. Lee, P. Hernandez, J. Lee, A. O. Govorov, and N. A. Kotov, Nature Materials 6, 291 (2007).
3:30 PM - **PP2.4
Preclinical Characterization of Nanomaterial Intended for Cancer Imaging and Therapy.
Anil Patri 1 Show Abstract
1 , NIH/NCI, Frederick, Maryland, United States
Engineered nanomaterial offer great potential to radically change disease detection, diagnosis, treatment, and prevention. Targeted drug delivery with nanomaterial alters the pharmacokinetics, pharmacodynamics, enhances solubility of hydrophobic drugs and delivers a therapeutic to a disease site with unprecedented specificity. This approach minimizes dosage, which reduces toxicity and side effects, while increasing the therapeutic benefit. There is an urgent need to quickly transition these novel technologies to benefit those that are suffering from insidious diseases such as cancer, while being cautious of the impact their production and use will have on the environment and health.The complex nature of nanomaterial poses challenges in their reproducible synthesis, scale-up, isolation, purification, characterization, along with their in vitro and in vivo safety and efficacy assessment. Addressing these challenges, develop methodologies and standards, requires multi-disciplinary team of scientists, expertise, appropriate instrumentation, methods, and resources. To address these challenges, the National Cancer Institute (NCI) has established the Nanotechnology Characterization Laboratory (NCL) in a formal scientific interaction and collaboration with National Institute of Standards and Technology (NIST) and U.S. Food and Drug Administration (FDA) to help facilitate transition of promising novel technologies to clinic. This presentation will focus on the resources available to cancer researchers at the Nanotechnology Characterization Laboratory (NCL) to conduct pre-clinical characterization and assessment of nanomaterial intended for cancer diagnosis, imaging, and therapy. The research outcome will help the community at large and facilitate development of standard protocols and assay development for regulatory review. Several tools and techniques to evaluate the material properties will be discussed. Standards development activities in collaboration with organizations such as ASTM will be presented.Funded by NCI Contract N01-CO-12400
4:30 PM - **PP2.5
Bioluminescent Quantum Dot Conjugates for Biosensing and In vivo Imaging.
Jianghong Rao 1 , Min-Kyung So 1 , Zuyong Xia 1 , Hequan Yao 1 , Yan Zhang 1 , Yun Xing 1 Show Abstract
1 , Stanford, Stanford, California, United States
Semiconductor quantum dots (QDs) offers attractive optical properties as fluorescence probes for biological imaging and detection. These QDs require external excitation light in order to fluoresce. Here we will present a different type of QD conjugate that can fluoresce via bioluminescence resonance energy transfer (BRET). We conjugated a mutant of Renilla luciferase (Luc8) to the QDs. The formation of the conjugate results in an energy transfer phenomenon between Rluc8 (as the donor) and QDs (as the acceptor) — BRET. Luc8 oxidizes its substrate, coelenterazine, and produces luminescence emission at a wavelength of 460–490 nm. When the QD conjugates are exposed to coelenterazine, the energy released in the oxidation of the substrate is transferred to the QDs through BRET, generating light emission from the QDs. Several methods will be described to prepare the bioluminescent QD conjugates. The BRET ratio varied with the conjugation methods and conditions, and can be as high as 2.30. Examples of this QD-BRET system as QD nanosensors for the multiplex detection of enzyme activity will be presented. The QD conjugates were injected into a nude mouse and gave strong BRET emissions. The long wavelength BRET emissions were more easily detected, especially in deep tissues. Cells labeled with bioluminescent QDs were readily imaged in the lungs after i.v. injection, but were not detectable with fluorescence imaging. We also examined the possibility of multiplexed bioluminescence imaging in vitro and in the living mouse with QDs. Since these QD conjugates can emit light without external illumination, thus the issue of high fluorescent background strong autofluorecence background with fluorescence imaging is avoided. These unique features of BRET-based QDs should open many new avenues for QD-based nanosensor design and imaging in living subjects, especially for imaging biological events at deep tissues in small living animals.
5:00 PM - PP2.6
Self-light Emitting Polymer Nanoparticles for in vivo Imaging of Hydrogen Peroxide.
Dongwon Lee 1 , Sirajud Khaja 1 , Juan Velasquez-Castano 2 , Madhuri Dasari 1 , Carrie Sun 3 , John Petros 3 , Robert Taylor 2 , Niren Murthy 1 Show Abstract
1 Biomedical Engineering, Gerogia Institute of Technology, Atlanta, Georgia, United States, 2 Cardiology Division Department of Medicine, Emory University, Atlanta, Georgia, United States, 3 Department of Urology, Emory University, Atlanta, Georgia, United States
Hydrogen peroxide is a small molecule metabolite in living organisms and plays a fundamental role in cellular signaling pathways that affect cell proliferation and cell death. However, the overproduction of hydrogen peroxide has been implicated in the development of numerous life-threatening diseases, such as atherosclerosis, neurodegenerative diseases, and cancer. Despite the significance of hydrogen peroxide in human health, at present, there are no contrast agents that can image hydrogen peroxide in vivo. Imaging of hydrogen peroxide in vivo has been challenging because of its low concentration and low reactivity in comparison to other reactive oxygen species. Therefore, there is great need in developing contrast agents that can image hydrogen peroxide in vivo, with high sensitivity and selectivity. Here, we present for the first time in vivo imaging of hydrogen peroxide using chemiluminescent nanoparticles based on peroxalate chemiluminescence, which involves hydrogen peroxide oxidation of oxalate esters in the presence of fluorophore. The strategy of hydrogen peroxide imaging using peroxalate chemiluminescence is to develop peroxalate ester polymer nanoparticles that encapsulate fluorescent dyes. Peroxalate ester polymers were synthesized through the reaction of hydroxybenzyl alcohol, octanediol and oxalic chloride. Chemiluminescent nanoparticles were formulated from peroxalate polymers and fluorescent dyes by an emulsion-solvent evaporation method. Chemiluminescent nanoparticles image hydrogen peroxide by performing a three component chemiluminescence reaction; first, hydrogen peroxide diffuses into the nanoparticles and reacts with peroxalate esters to generate a high energy intermediate dioxetane, second, dioxetane chemilcally excites fluorescent dyes through a chemilcally initiated electron exchange transfer mechanism, leading to light emission upon relaxation and imaging of hydrogen peroxide. Peroxalate nanoparticles emit fluorescent light in response to hydrogen peroxide at tunable wavelengths (460-630nm), and have nanomolar sensitivity for hydrogen peroxide and excellent specificity for hydrogen peroxide over other reactive oxygen species. Peroxalate nanoparticles were also capable of detecting hydrogen peroxide in the peritoneal cavity of mice, during an LPS-induced inflammatory response. We anticipate numerous applications of peroxalate nanoparticles for in vivo imaging of hydrogen peroxide, given their high specificity, sensitivity, and deep tissue imaging capability.
5:15 PM - PP2.7
Light Emission Properties and Biological Applications of Lanthanide Doped Oxide Nanoparticles.
Genevieve Mialon 1 , Melanie Moreau 1 , Didier Casanova 2 , Thanh-Liem Nguyen 2 , Antigoni Alexandrou 2 , Thierry Gacoin 1 , Jean-Pierre Boilot 1 Show Abstract
1 Laboratory of Condensed Matter Physics, CNRS, Ecole Polytechnique, Palaiseau France, 2 Laboratory for Optics and Biosciences, CNRS-INSERM, Ecole Polytechnique, Palaiseau France
Rare-earth doped oxides as bulk materials are well known for their numerous applications in light emitting devices. Emission properties of nanoparticles, in association with their small size, open the way to new applications such as the elaboration of transparent luminescent devices or new biological labels. The key issue for such applications is the control of the surface state of the particles in order to preserve their dispersion state, to guarantee a strong emission and/or ensure strong interactions with specific target sites.Our work in this field mainly concerns yttrium vanadate particles (YVO4:Ln with Ln=Eu, Dy and Yb/Er) that are obtained as aqueous suspensions through a simple reaction of coprecipitation . As compared to the bulk material, these particles (10-40 nm in diameter) exhibit the characteristic emission from the lanthanide dopant but with a lower efficiency (quantum yield of 15% and emission lifetime of 0.7 ms). The first part of our work is devoted to the improvement of the emission properties of particles. Our results show that the emission process is altered either by surface hydroxyl groups or by the poor cristallinity of the particles. We show that large improvement can be obtained following an original process which allows recovering the particles as colloidal dispersions after their thermal treatment at 1000°C. In the case of Eu3+ doped particles, quantum yield and emission lifetime were increased up to 40% and 0.8 ms respectively without notable increase of particle size. Moreover, the emission spectrum, either from colloidal suspensions or from single particles fits almost perfectly to the one from the bulk material.The second part of our work is devoted to the surface derivatization of the particles for applications as biological probes . We chose a general scheme involving the coating of the nanoparticles with a thin layer of amino-silane. This process was chosen in order to allow further versatile grafting reactions trough the surface amino groups. This strategy will be detailed in the case of the coupling between our particles and a protein through the use of a homo-bifunctional cross-linker. The quantification of the number of attached proteins was achieved using dual-color microscopy and fluorescently-tagged proteins, by observing the step-like photobleaching of the organic fluorescent tag. The observation of labelled toxins interacting with living cells shows the high potentiality of rare-earth-doped oxide particles as new biological probes.  A. Huignard et al., Chem. Mat. 12, 1090 (2000) ; A. Huignard et al., Chem. Mat. 14, 2264 (2002) E.Beaurepaire et al, Nano Lett. 4, 2079 (2004) ; D.Casanova et al. Appl. Phys. Lett. 89, 253103 (2006); D.Casanova et al., J. Phys. Chem. B, 110, 19264 (2006)
5:30 PM - PP2.8
Fluorescent Silica Nanoparticles as Biological Probes and Sensors.
Andrew Burns 1 , Erik Herz 1 , Jin Hyang Choi 2 , Ethan Chiang 3 , Alexander Nikitin 2 , Barbara Baird 3 , Ulrich Wiesner 1 Show Abstract
1 Materials Science & Engineering, Cornell University, Ithaca, New York, United States, 2 Biomedical Engineering, Cornell University, Ithaca, New York, United States, 3 Chemistry and Biochemistry, Cornell University, Ithaca, New York, United States
Sol-gel silica is an excellent host material for the development of functional hybrid nanoparticles as probes and sensors for biology and nanomedicine. The facile and versatile chemistry of silica allows for the realization of many architectures, tuned to specific applications as well as the incorporation of functional groups including dyes, chelators and polymers. As well, its benign surface chemistry is well-suited to both in vitro and in vivo assays. Our earlier work has shown that particles containing a core of silica-bound dye molecules surrounded by a pure silica shell exhibit exceptional brightness and stability compared to the constituent dyes as a general trend for dyes across the UV/visible spectrum. In addition to in vitro studies, we have applied these nanoparticles to biological questions in vivo, investigating the applications of these particles to clinically-relevant tasks such as sentinel lymph node mapping, as well as in modeling systems such as cell trafficking in metastatic cells. This core/shell design has been further developed as a platform for quantitative ratiometric sensing and imaging of ion concentrations in biological samples. The co-localizaton of reference and sensor dye molecules in separate layers of a core-shell architecture yields quantitative sensors with high surface area for analyte interaction, while protecting the reference signal in the core. We have produced core-shell sensor particles with average radii below 6 nm which are capable of delivering high local concentrations of pH or Ca+2 sensor dye to biological microenvironments which were previously un-reachable by larger probes, such as synaptic vesicles at axon/dendrite junctions.
5:45 PM - PP2.9
A New Route to Synthesize Alloyed Semiconductor Quantum Dots of CdSe1-xTex with Good Thermal Stability and Promising Bio-application.
Kang Sun 1 , Wanwan Li 1 , Bin Xing 1 , Hongjing Dou 1 , Jiebing Wang 1 , Pengfei Zhang 1 Show Abstract
1 State key lab of metal matrix composites, Shanghai Jiao Tong University, Shanghai China
The red to near-infrared (IR) wavelength window (600-900 nm) is rapidly emerging as an important region of the electromagnetic spectrum for biological imaging and detection. Unfortunately, there are relatively few near-IR-emitting organic fluorophores available, and these near-IR-emitting organic fluorophores tend to photobleach and have a narrow absorption profile and broad emission full width at half-maximum (FWHM). These problems limit the use of current organic-based near-IR-emitting fluorophores for ultrasensitive and multiplexed biological imaging and detection. With the introduction of quantum dots (QDs) to the biological community, the ability to design near-IR-emitting fluorescence probes is expected to be rather simple, because the optical emission of QDs can be tuned by size, shape, and composition. Recently, alloyed semiconductor quantum dots of cadmium selenium telluride (CdSe1-xTex) have been developed to achieve continuous tuning of the optical properties without changing the particle size. With red-shifted light emission up to 850 nm and quantum yields up to 60%, this new class of alloyed quantum dots opens new possibilities in band gap engineering and in developing near-infrared fluorescent probes for biological imaging and biomarker detection. However, expensive and toxic phosphines were used as coordinating solvents for the synthesis procedure, which limits the production of CdSe1-xTex QDs in organics to milligram quantities. Therefore, investigations on synthesis of CdSe1-xTex QDs in phosphine-free organics have become important and attractive.Our contribution details a new route to prepare high quality CdSe1-xTex QDs in paraffin liquid at relatively low temperatures (200°C-260°C). Paraffin liquid and oleic acid were used as the solvent and ligand instead of expensive and toxic phosphines of tri-n-octylphosphine (TOPO) and hexadecylamine (HAD). By investigating in detail the effect of changing Te to Se molar ratio of the precursors, the concentration of the precursors, reaction temperature and the quantity of the ligand, it is possible to obtain CdTe QDs with high PL quantum yield (up to 70% at the room temperature), broad emission spectra ranging from 600nm to 820nm and narrow FWHM between 40~50nm. The thermal stability of the alloyed quantum dots was also studied. With temperature increasing from 10 to 60°C, the PL intensity of the prepared CdSe1-xTex QDs declined by less than 20% without any change of the absorption spectra, suggesting that these alloyed QDs have good thermal stability, which is an important property for their bio-applications. Moreover, the as-prepared CdSe1-xTex QDs were successfully embedded into the porous polystyrene (PS) beads capped with carboxylic acid groups to fabricate optically encoded beads, which suggests their promising application in multiplexed bioassays.
PP3: Poster Session: Synthesis, Characterization and Applications in Biology I
Tuesday AM, November 27, 2007
Exhibition Hall D (Hynes)
9:00 PM - PP3.1
FRET-Based Quantum Dot-DNA Molecular Probes for Detection of Avian Flu Virus.
Youngseon Choi 1 , Haejin Kwon 1 , Jeeyong Ryu 1 , Sunhee Lim 1 , Jaeseung Kim 2 , Alexey Dan-Chin-Yu 3 , Rita Song 1 Show Abstract
1 NanoBio Chemistry, Institut Pasteur Korea, Suwon Korea (the Republic of), 2 Medicinal Chemistry, Institut Pasteur Korea, Suwon Korea (the Republic of), 3 Diagnostics, Institut Pasteur Korea, Suwon Korea (the Republic of)
Detection of specific DNA sequence targets in a highly sensitive and quantitative manner is critical in identification of biomarkers in various infectious and genetic diseases. Conventional approaches based on small organic dyes or fluorophore labeled proteins are limited due to the intrinsic background signal giving false positive signal as well as photobleaching. Recently, CdSe/ZnS quantum dots (QD) modified with molecular recognition agents such as oligonucleotides, peptides, and antibodies, have been of great interest as ultrasensitive and specific molecular probes due to their remarkable photophysical properties including high quantum yield, narrow size-tunable photoluminescence, and well-known photostability. Specifically, QDs as FRET donors have been utilized to detect nucleic acids for the potential application to gene expression assay and single nucleotide genotyping. In this study we sought to develop QD-based Taqman® type probe for the sensitive detection of DNA derived from Avian Flu Virus (H5N1). As a proof-of-concept experiment, we designed QD-DNA probes via either ligand exchange reaction or conjugation chemistry. Dye-incorporated oligonucleotides as FRET quencher was attached to CdSe/ZnS QDs, then hybridized with the target DNA. Hybridization of the probe with the target was confirmed by agarose gel electrophoresis and fluorescence spectroscopy, and fluorescence microscopy. FRET efficiency of the probes and the recovery of QD fluorescence upon the enzyme treatment will be investigated with regard to the number of dye-incorporated DNAs per QD and the conditions for enzyme reactions.
9:00 PM - PP3.10
Monolayer Protected Clusters of Gold (AuMPCs): Synthesis and Characterization.
Neerish Revaprasadu 1 , Ndabenhle Sosibo 1 , Robert Tshikhudo 2 Show Abstract
1 Chemistry, University of Zululand, Empangeni, KZN, South Africa, 2 Project AuTek, Mintek, Randburg, Gauteng, South Africa
High affinity thiolate-based ligands have been shown to impart a great deal of stability onto the monolayer protected clusters (MPCs). Due to the extreme stability of the gold-sulfur bond, the ligand forms a protective layer around the gold core and controls the subsequent properties of the resultant clusters.1 The choice of ligand controls the hydrophilicity and biocompatibility of the clusters. Thiolated-poly(ethylene) glycol (PEG) based ligands have found a popular use due to their water solubility and capping power as protective agents on gold surfaces. Many applications in nanobiology and nanomedicine have benefited from the biomolecular conjugates of these AuMPCs. Specific areas such as diagnostics, drug delivery, and gene delivery have taken advantage of the use of specifically tailored MPCs.2Synthesis and characterization of gold monolayer protected clusters capped with different sulfur-based water soluble ligands will be presented. Conjugation of these materials with selected biomolecules such as proteins will be presented. Multiple ligand capping of gold clusters yielding mixed MPCs (MMPCs) will also be presented. Results from techniques such as UV-Vis, TEM and agarose gel electrophoresis will be presented.
9:00 PM - PP3.11
Distribution and Aggregation of Gold Nanorods in Living Cells.
Yasuro Niidome 1 , Keisuke Higashimoto 1 , Yukichi Horiguchi 1 , Naotoshi Nakashima 1 Show Abstract
1 , Kyushu University, Fukuoka Japan
Uptake processes of nanoparticles into targeted cells have been studied to understand and design the functions of the nanoparticles in in vivo and in vitro systems. Gold nanorods are rod-shaped gold nanoparticles which are synthesized in micellar solutions of cationic amphiphiles. Colloidal gold nanorods passivated with phosphatidylcholine were taken up in cultivating cells, and formed aggregates. The aggregates efficiently scattered the light. In addition, the PC-nanorods accumulated in (or on) nuclei without additional modification of the functional molecules such as nuclear localization signal peptides.
9:00 PM - PP3.12
Protein-Nanoparticle Conjugates as a Potential Therapeutic Agents For Treatment of Hyperlipidemia.
Vladimir Reukov 1 , John Barry 1 , Alexey Vertegel 1 Show Abstract
1 Bioengineering, Clemson University, Clemson, South Carolina, United States
Atherosclerosis, the leading cause of death in the developed world, is responsible for more than half of the yearly mortality in the United States. One of the most important risk factors for atherosclerosis is hyperlipidemia, characterized by elevated blood levels of low-density lipoproteins (LDLs). Excessive LDLs can accumulate in the vicinity of a small vascular injury, forming so-called fatty streaks, the first manifestation of atherosclerotic plaque. Hyperlipidemia is often related to the lack of LDL receptors in hepatocytes, which consequently couldn’t recognize LDLs and makes their further metabolism impossible . Here, we show that nanoparticles can be used to enhance delivery of low-density lipoproteins to liver via alternative route of uptake by liver macrophage (Kupffer) cells, which eventually results in their digestion by lysosomes and thus, provides the pathway similar to that of normal LDLs uptake by hepatocytes. Monoclonal antibody to human apolipoprotein-B (Apo-B100, Meridian Life Science Inc., ME) was covalently attached to 100 nm chloromethylated polystyrene latex nanoparticles. Tween 20 was used to remove physically adsorbed enzyme. The amount of the antibody covalently attached to nanoparticles was quantified using fluorescent labeling. To study binding of nanoparticles to LDL, LDLs were FITC labeled, mixed with the suspension of unlabeled antibody-nanoparticle conjugates, and incubated for 2 hours at room temperature. The suspension was then centrifuged at 2,000 g to precipitate only nanoparticles with bound LDLs, but not free LDLs, from the suspension. The supernatant was then removed and fluorescence was measured using a microplate reader, pellet was resuspended in same amount of the buffer. Uptake of fluorescently labeled LDL-nanoparticle complexes by Kupffer cells was studied using a fluorescence microscope. Kupffer cell cultures, harvested from chicken liver, were treated with fluorescently-labeled LDL-nanoparticle complexes and incubated for 4 h at 37°C. The cells were then carefully washed 4 times by 3 mL of PBS buffer (37°C). Suspension of fluorescently labeled free LDLs was used as a control. After washing, cells were investigated with the microscope to determine whether or not binding to macrophages had occurred. After that live/dead cell assay kit was used to check viability of treated Kupffer cells. Future work will focus on utilization of more biodegradable nanoparticles (such as PLA or polyketals) and nanodevices uptake by liver and their toxicity in animal models.
9:00 PM - PP3.13
Facile Fabrication and Near-Infrared Localized Surface Plasmon Resonance Properties of Two-dimensional PS@Au Core/Shell Nanoparticle Arrays, and Their Use as a Ultra-sensitive Bio-sensors.
Zettsu Nobuyuki 1 , Shuhei Uchida 1 , Kazuya Yamamura 1 , Katsuyoshi Endo 1 Show Abstract
1 Recearch Center for Ultra-Precision Science and Technology, Osaka University, Suita, Osaka, Japan
The location of localized surface plasmon resonance (LSPR) peaks in the visible region from an individual gold nanoparticle is instrumental to various colorimetric applications that involve the use of the naked eye to detect color changes. For biological applications that require deeper penetration of near-infrared (NIR) light, to which both blood and soft tissue are highly transparent, a different type of Au nanostructure is required. We demonstrated here facile fabrication and characterization of PS@Au core-shell nanoparticles array through a combination with colloidal self-assembly and atmospheric pressure plasma glow discharge treatment, which find use in application such as in-situ monitoring of bio-medical event in blood. The desired two-dimensional (2D) PS@Au core/shell nanoparticles arrays were prepared in three steps including fabrication of 2D PS nanoparticles array using colloidal self-assembly, size tuning of PS nanopaticles under atmospheric helium (He) plasma glow discharge, and Au vacuum evaporation coating onto the PS nanoparticles array. We found the size and interparticle distance of PS@Au core/shell nanoparticles could be tuned well according to the change of particle shapes. There were two plasmon peaks at ca. 600 nm and 1000 nm, respectively. Decreasing size of PS@Au core/shell nanoparticles shifted the peak position in NIR region to longer wavelength, even though the peak in visible region remained unchanged the position. This suggested the peak at 600nm was contributed to the interaction between the PS@Au core/shell nanoparticles and the Si substrate. To understand this optical feature, we demonstrated Mie theory calculations for an individual PS@Au core/shell nanoparticle with 10nm shall thickness and 160 nm core diameter. The calculation indicated that the particle has an LSPR peak in the NIR region. We need further theoretical analysis such as finite different time domain (FDTD) electrodynamics to explain the SPR perk in visible region. We have further investigated two-dimensional (2D) PS@Au core/shell nanoparticles arrays on Si wafer as potential label-free optical transduction elements in a nanoscale biosensor. We found the LSPR peaks were clearly shifted when immersing the PS@Au core/shell nanoparticles arrays in different dielectric media.
9:00 PM - PP3.14
Synthesis of Monofunctional Gold Nanoparticles and Their Applications.
Qun Huo 1 Show Abstract
1 Nanoscience Technology Center, University of Central Florida, Orlando, Florida, United States
In the bottom-up approach towards nanomaterial development, there are two very important aspects to be addressed: one is the synthesis of nanobuilding blocks and the other one is how to assemble the nanobuilding blocks together into materials or devices with ideal structures, properties and functions. The property of a nanomaterial is not only dependent on individual nanobuilding blocks, but also affected dramatically by the architectural organization of nanobuilding blocks and their interactions. In order to achieve a precise control on the organized nanoassemblies, the chemical structure and functionality of individual nanobuilding blocks such as nanoparticles must be controlled at molecular levels. Recently our group developed a solid phase synthesis method to prepare monofunctional nanoparticles, gold nanoparticles that contain a single chemical functional group on the surface (Chem. Comm. 2004, 518-519; Langmuir 2004, 20, 8343-8351; Chem. Mater. 2004, 16, 3746-3755; J. Am. Chem. Soc. 2005, 127, 8008-8009). Using these molecular nanobuilding blocks, we can synthesize sophisticated nanoparticle/polymer hybrid materials such as “nanonecklaces”, “nanochains” and nanoparticle clusters from very simple and traditional chemical reactions, just like the total chemical synthesis of sophisticated natural organic compounds from smaller molecular units. These materials provide excellent opportunities for one to probe and study the inter-nanoparticle interactions in a quantitative fashion from different dimensions. An example of using this approach to improve the nonlinear optical property of gold nanoparticles will be presented, along with a few other potential applications of gold nanoparticles in different areas.
9:00 PM - PP3.15
Biological Properties of Cancer Cell Labeled with Visible Luminescent Nanocrystalline Silicon Particles and Visualization Observation in Mouse.
Keisuke Sato 1 2 , Masaki Hiruoka 2 , Kenji Hirakuri 2 , Kohki Fujioka 3 , Kenji Yamamoto 3 Show Abstract
1 Quantum Beam Center, National Institute for Materials Science, Tsukuba, Ibaraki, Japan, 2 Department of Electronic and Computer Engineering, Tokyo Denki University, Hikigun, Saitama, Japan, 3 Department of Medical Ecology and Informatics, International Medical Center of Japan, Shinjuku, Tokyo, Japan
Luminescent semiconductor nanoparticles such as cadmium sulfide (CdS) and cadmium selenide (CdSe) have been widely studied for application to biomedical engineering fields. These nanoparticle materials, however, have some problems for the safety to living organism, and the fluidity and excretion in living organism due to the increase of the particle size. Therefore, it is expected to develop the new nanoparticle materials with some features of non-toxic and minimal particle size. We have been fabricated the nanocrystalline silicon (nc-Si) particles, which continuously emits from red light up to blue light by reducing the size to 2.5nm or less. In this paper, biological properties of the cancer cell labeled with the nc-Si particles and the visualization observation in mouse will be discussed.HeLa cell was seeded in multi-well culture plate at a density of 5 × 104 cell/well and then was cultured in minimum essential medium (MEM) supplemented with 10 % fetal bovine serum at 37 °C in a 95 % O2-5 % CO2 humidified atmosphere for 48 hours. After that, the some well including the HeLa cell was added the MEM containing the nc-Si particles with a size of 2.5 nm and was cultured at 37 °C in a 95 % O2-5 % CO2 humidified atmosphere for 48 hours. The concentration of nc-Si particles added in the HeLa cell was varied from 2×10-4 μM to 200 μM. Moreover, the nc-Si particles were also directly injected into the lymphatic vessel of mouse by syringe. The injection concentration of nc-Si particles was 4.5 mg.The nc-Si particles were engulfed in the HeLa cell with a progress in the culture term. The viability of HeLa cell was very high for englobement concentration of nc-Si particles up to 200 μM. Moreover, strong red luminescence could be obtained from the HeLa cell with the nc-Si particles by irradiation of UV light. On the other hand, the nc-Si particles stably and smoothly flowed to the lymph node with the strong emission of red light after injection into the lymphatic vessel.
9:00 PM - PP3.17
Silicon Nanocrystal Conjugation to Streptavidin.
Jonghoon Choi 1 2 , Peter Niarhos 1 , Nam Sun Wang 1 , Vytas Reipa 2 Show Abstract
1 Chemical and Biomolecular Engineering, University of Maryland, College Park, Maryland, United States, 2 Biochemical Science, National Institute of Standards and Technology, Gaithersburg, Maryland, United States
The high affinity and specificity of avidin–biotin interactions are used for diverse applications in immunology, histochemistry, and in situ hybridization. Silicon nanocrystals (SNs) have been recently recognized as efficient and biocompatible fluorescence tags. We have covalently attached photoluminescent SNs to streptavidin. Selective conjugation of SNs to a target protein is accomplished through a multistep surface modification of SNs. In the first step, alkane monolayer is attached to freshly prepared hydrogen terminated SNs through photo catalyzed hydrosilylation. Alkane provides a chemical linkage to the hetero bifunctional cross linker (4-azido-2,3,5,6,-tetrafluorobenzoic acid, succinimidyl ester), and stabilizes the nanoparticle against oxidation in aqueous environment. Next, an open end of bifunctional cross linker is reacted with streptavidin, and forms an amide linkage by way of succinimidyl ester reaction. Gel electrophoresis with fluorescence detection of the conjugate mixture shows distinct separate bands, corresponding to the free and multiparticle tagged streptavidin. Streptavidin functionality was tested by allowing the tagged protein to interact with biotinylated micro beads that displayed efficient photoluminescence after separation and thorough washing. Bright conjugate photoluminescence combined with the low SNs cytotoxicity offers an attractive fluorescence labeling platform for biological assays.
9:00 PM - PP3.18
Self-assembled Organic Nanoparticles for Immunofluorescence Labeling.
Hyong-Jun Kim 1 , Jiseok Lee 3 , Tae-Hoon Kim 5 , Taek Seung Lee 5 , Jinsang Kim 1 2 3 Show Abstract
1 Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States, 3 Macomolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States, 5 Advanced Organic Materials and Textile System Engineering, Chungnam National University, Daejon Korea (the Republic of), 2 Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States
Fluorescence labeling is a very important analytical technique for probing the structure of living cells. Since the introduction of the semi-conducting quantum dot, many researches have been focused on inorganic quantum dots for immunofluorscence labeling due to their high quantum yield, high molar extinction coefficients, broad absorption with narrow light emission, and good photo physical and chemical stability. Despite of these promising properties of semi-conducting quantum dots for fluorescence labeling, cyto-toxicity is a critical problem in any living cell or animal experiments. Alternative choices are dye-loaded latex particles and dye-doped silica colloids having improved photostability compared to conventional dye molecules. However, dye-loaded particles also have a critical limit of brightness due to the self-quenching when high density of dyes present at the nanoparticle surface. Thus, developing highly emissive, biocompatible, and chemically readily modifiable luminescent materials is strongly desired.In this presentation we will describe the development of highly emissive and highly photo-stable organic nanoparticles for immunofluorescence labelling. We developed a new benzoxazole molecule and self-assemble them with functionalized diacetylene molecules to obtain well organized spherical nanoparticles with 80nm diameter. The nanoparticles show largely enhanced green fluorescence having the quantum yield of 38% compared to the 3% in a solution. Intermolecular hydrogen bonding through J-aggregation is likely the origin of the high quantum yield of the nanoparticles. The benzoxazole nanoparticles were assembled with biotin-functionalized diacetylene molecules and used to selectively bind to patterned avidin on a solid substrate to demonstrate its application for the immunofluorescence labeling. Recognition-induced fluorescence development in the PDA passivation layer produce additional red emission providing the unique dual color emission capability to the PDA-oxadiazole nanoparticles.
9:00 PM - PP3.19
Synthesis of Cu-In-S Fluorescent Nanocrystals.
Kousuke Watanabe 1 , Masato Uehara 2 , Hiroyuki Nakamura 2 , Hideaki Maeda 1 2 3 Show Abstract
1 Department of Molecular and Material Sciences, Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, Fukuoka Pref., Japan, 2 , National Institute of Advanced Industrial Science and Technology (AIST), Tosu, Saga Japan, 3 , JST, CREST, 4-1-8 Hon-chou, Kawaguchi, Saitama, Japan
Semiconductor nanocrystals (NCs) have received much attention due to their many applications particularly as fluorescence tags for biological molecules, and as tunable LEDs. The colloidal II-VI type semiconductor NCs are easily produced in organic solvent because they favor ionic bonding. However, most of II-VI type semiconductor NCs which are used in visible and near-infrared fluorescence include toxic elements. Therefore, we focused on the chalcopyrite materials. Chalcopyrite I-III-VI2 semiconductors such as CuInS2 and CuInSe2 are direct transition semiconductors which favor ionic bonding just like the II-VI type materials. These materials have a wider range of choices for elements. In addition, their properties have been investigated intensively, particularly in relation to their application as photovoltanic components of solar cells. CuInS2 (CIS) has a band gap energy of 1.5eV and is expected to show photoluminescence (PL) from visible range to near-infrared range by quantum effect. In this study, we synthesized CIS fluorescent NCs by heating organic metal complex, and investigated the relationship between optical and structural characteristics of the synthesized CIS NCs. The raw material solution was prepared by separate dissolution of copper iodide (I) and indium iodide (III) in oleylamine, and thioaceteamide in trioctylphosphine. The dissolved components were mixed together and the mixture was used as the raw material solution. This raw material solution was subjected to different reaction conditions such as heating from 160 to 240 °C for 3 to 60 sec using a microreactor. In several runs, the products were immersed in an organic solvent containing Zn2+, Cd2+ or Ag+ and heated at 180 °C as a post-treatment.In all product solutions, we observed the red light emission at ambient temperature by irradiation with black light. In the optical spectra, the absorption and PL emission peak was shifted to longer wavelength with an increase in synthesis temperature. The PL emission peak varied from 620 to 680 nm. The maximum quantum yield (QY) of 6% was obtained under the reaction condition of 200 °C for 10 sec. The crystal phase of all products was confirmed as tetragonal phase by XRD. The average sizes obtained from HRTEM observations ranges from 2.5 to 3.5 nm.Furthermore, we successfully improved QY of CIS NCs by our post treatment procedure, that is, by re-heating the CIS NCs dispersed in organic solvent containing a particular metal salt (Zn2+, Cd2+ or Ag+). The observed effects of metal ions to nanocrystal properties varied. In the case of zinc or cadmium, considerable improvements from the original 6% QY to higher yields of 25 - 35% were observed.
9:00 PM - PP3.2
Stability, Cytotoxicity, and Cell-uptake of II-VI Semiconductor Nanoparticles.
Andrea Salcher 1 , Marija Nikolic 1 , Tatjana Achenbach 2 , Horst Weller 1 2 Show Abstract
1 Physical Chemistry, University Hamburg, Hamburg Germany, 2 , Center for Applied Nanotechnology, Hamburg Germany
Colloidal II-VI semiconductor quantum dots, especially in their advanced form as core-shell and core-shell-shell nanocrystals, are very promising materials in Biomedicine. They are used as target diagnostic cancer-imaging agents, as aids to optically guided surgery, as smart drug-delivery systems, and as biosensors. Compared to conventionally used organic fluorophores, these nanoparticles have a variety of advantages such as narrow emission spectra, broad absorption spectra, a tunable emission according to their size, and above all their excellent resistance to photobleaching. Much progress has been made in this field recently, however the toxicity and the uptake of the nanoparticles into cells are only partially investigated[1,2].We present highly monodisperse CdSe/CdS core-shell and CdSe/CdS/ZnS core-shell-shell nanocrystals synthesised in organic solvents at high temperatures[3,4]. In order to use them in Biomedicine they have to be water soluble. We developed a method to bring them into water by ligand exchange with modified poly(ethyleneoxide). For the purpose of near-infrared fluorescent probes for in vivo molecular imaging alloyed semiconductor nanoparticles (e.g. cadmium selenide telluride) have been produced following the well-established CdSe synthesis. Our results demonstrate that a partial ion exchange can be successfully used to tune the optical and electronic properties.First results in activating and conjugating the nanoparticles to biological molecules and in vitro experiments using cell-culture models will be shown.References: Bruchez et al, Science, 1998, 281, 2013. Hardman, Environmental Health Perspectives, 2006, 114, 165. Mekis et al., J. Phys. Chem. B, 2003, 107, 7454. Eychmüller, J. Phys. Chem. B, 2000, 104, 6514. Nikolic et al., Angew. Chem. Int. Ed., 2006, 45, 6577.
9:00 PM - PP3.20
Surface Enhanced Raman and Infrared spectroscopy (SERS and SEIRA) of Ibuprofen Intercalated Hybrid Bilayer Nanoshells.
Carly Levin 1 , Janardan Kundu 1 , Benjamin Janesko 1 , Gustavo Scuseria 1 , Robert Raphael 2 , Naomi Halas 1 2 3 Show Abstract
1 Chemistry, Rice University, Houston, Texas, United States, 2 Bioengineering, Rice University, Houston, Texas, United States, 3 Electrical and Computer Engineering, Rice University, Houston, Texas, United States
9:00 PM - PP3.4
The Effects of Chemical Functionalization vs. Biological Functionalization on Nanoparticle Binding Affinity.
Julia Patrone 1 , James Crookston 1 , Huong Le 1 , Jason Benkoski 1 , Jennifer Sample 1 Show Abstract
1 RTDC, JHU Applied Physics Laboratory, Laurel, Maryland, United States
Due to their small size, high diffusivity, and chemically active surfaces, nanoparticles share much in common with water-soluble proteins. These similarities have generated great interest in using biofunctional nanoparticles as a route to deliver targeted therapeutics. Already nanoparticles have found applications in the hyperthermia of tumors, personal care lotions, and tissue scaffolding. Our study focuses on the targeting of such nanoparticles to specific biological sites. It therefore seeks to identify the factors that control the migration and capture of nanoparticles within living systems. In particular, we examine the affinity of anti-collagen coated magnetite nanoparticles for collagen IV-coated surfaces and for epithelial tissue culture cell line. The studies are performed in vitro within microfluidic devices that are designed to mimic various fluid flow patterns within the body. We find, in this case, a large background signal due to nonspecific binding. Further examination shows a correlation between chemical functionality (e.g., surface charge, hydrophilicity) that suggests that a balanced approach between biological functionality and chemical functionality may reduce the background from nonspecific binding to acceptable levels.
9:00 PM - PP3.5
Designed Fabrication of Multifunctional Nanomaterials for Biomedical Applications.
Jaeyun Kim 1 , Ji Eun Lee 1 , Taeghwan Hyeon 1 Show Abstract
1 National Creative Research Initiative Center for Oxide Nanocrystalline Materials, and School of Chemical and Biological Engineering, Seoul National University, Seoul Korea (the Republic of)
Clever combinations of different nanoscale materials will make it possible to develop new multifunctional nano-biomedical platforms for simultaneous targeted delivery, fast diagnosis, and efficient therapy. In this presentation, I would like to present designed fabrication of multifunctional nanostructured materials based on nanoparticles and nanoporous materials and their bio-medical applications. Multifunctional nanoporous silica spheres embedding uniform magnetite and quantum dot nanoparticles were synthesized (J. Am. Chem. Soc. 2006, 128, 688). The resulting multifunctional nanomaterials have the high surface area and large pore volumes, derived from mesoporous silica, and the superparamagnetic and luminescent properties, come from incorporated nanoparticles. The drug loading and controlled release of them from multifunctional mesoporous silica spheres were demonstrated. A simple, reproducible, and general method of preparing multifunctional nanoparticle assemblies on silica spheres was developed (Angew. Chem. Int. Ed. 2006, 45, 4789). Magnetite nanoparticles synthesized in an organic phase were covalently bonded onto silica spheres through a simple nucleophilic substitution reaction between terminal bromo-groups of ligands of nanoparticles and amino-functional groups of silica spheres. Using these magnetite nanoparticle/silica sphere composites as supports for further assembly of nanoparticles, multifunctional nanoparticle/silica sphere assemblies could be prepared. Nanoparticles of Au, CdSe/ZnS, or Pd were assembled on free residual amino groups of silica spheres. These multifunctional nanoparticle/silica sphere assembly exhibited combined properties of magnetism with surface plasmon resonance, luminescence, or catalysis. Multifunctional magnetic gold nanoshells (Mag-GNS) consisted of gold nanoshells embedding magnetite (Fe3O4) nanoparticles were synthesized and anti-HER2/neu was conjugated to Mag-GNS for targeted MRI and NIR photothermal therapy of cancer cells (Angew. Chem. Int. Ed. 2006, 45, 7754). SKBR-3 cells targeted with Mag-GNS exhibited darker T2-weighted images than control cells, and were rapidly destroyed upon short exposure to femtosecond laser pulses with an NIR wavelength and a low power. Finally, multifunctional polymer nanoparticles for the cancer-targeted MRI and drug delivery were synthesized. The magnetite nanoparticles and the doxorubicin were encapsulated in biodegradable PLGA polymer matrix. The surface of the polymer nanoparticles were functionalized PEG-folic acid conjugate to target the folate receptors expressed on cancer cells (KB cells). The cancer specific targeting of the multifunctional polymer nanoparticles resulted in MRI detection and therapy of the cancer cells. In addition, magnetite nanoparticles loaded in the polymer nanoparticles imparted the magnetic guiding, providing enhanced synergetic cancer-targeting in company with the folic acid targeting.
9:00 PM - PP3.6
Fluorescent and Magnetic Resonance Imaging by Rare Earth Doped Nanoparticles with Garnet Structure.
Ryo Asakura 1 , Hiroshi Sakane 1 , Kunihiro Noda 1 , Tetsuhiko Isobe 1 , Masahito Morita 2 3 , Toshiro Inubushi 2 Show Abstract
1 , Keio University, Yokohama Japan, 2 , Shiga University of Medical Science, Otsu Japan, 3 , PRESTO, JST, Saitama Japan
Organic dyes commonly used for quantitative analysis of protein and imaging of tissue. However, they have some problem such as fading on preservation and observation. Inorganic nanosized phosphors with garnet structure are one of the key materials to break through these problems. We have already reported the glycothermal synthesis of Y3Al5O12:Ce3+ (YAG:Ce3+) nanophosphor of ~10 nm in diameter . Biotinylated YAG:Ce3+ nanoparticles tagged avidin-immobilized microbeads through the specific avidin-biotin interaction and a green emission image was obtained under blue light excitation with a fluorescent microscope .In this work, we focus on nanoparticles with functions of either near infrared (NIR) fluorescence or MR contrasting enhancement and both of them. The transmittance of NIR light through tissues is so high. NIR light hardly induces autofluorescence from tissue. Therefore, we can improve the sensitivity of imaging using excitation and emission in the NIR region. Moreover, a fluorescent-MR contrasting multimodal probe enables us to take fluorescent and MR images using a single probe. Here we synthesize rare earth doped nanoparticles with garnet structure, which work as a NIR fluorescent probe and MR contrast agent, and characterize their properties.Nanoparticles with garnet structure such as Y3(1-x)Gd3xAl5O12 and Gd3Ga5O12 were synthesized from acetates, acetylacetonates and alcoxides and so on by autoclave treatment in a coordinating glycol solvent with a high boiling point, e.g., 1,4-butanediol. The as-prepared and low-temperature heated particles were well-dispersed in water. According to X-ray diffraction profiles, their crystal structure are garnet-type and they contain no byproduct. Moreover, we doped a NIR emission centers such as Yb3+ and Tm3+ into garnet crystal. Yb3+-doped nanoparticles after heating at temperatures over 600 oC show the emission at 1030 nm corresponding to the f-f transition of Yb3+ under the NIR excitation. Nanoparticles containing Gd element were dispersed in agarose gel and T1-weighted MR images depended on their concentration. These nanoparticles are expected to be applied for bioimaging. R. Kasuya, T. Isobe, H. Kuma, J. Katano, J. Phys. Chem. B., 109, 22126 (2006). R. Asakura, T. Isobe, K. Kurokawa, H. Aizawa, M. Ohkubo, Anal. Bioanal. Chem., 386, 1641 (2006).
9:00 PM - PP3.7
Gold Nanocages for Biomedical Applications: Recent Advances.
Sara Skrabalak 1 , Leslie Au 1 , Jingyi Chen 1 , Xingde Li 1 , Younan Xia 1 Show Abstract
1 , University of Washington, Seattle, Washington, United States
Gold nanocages are hollow and porous nanostructures with edge lengths < 100 nm. They are synthesized by the galvanic replacement reaction between Ag nanocubes and HAuCl4. By controlling the amount of HAuCl4 added to the reaction media, the position of the surface plasmon resonance peak of the resultant Au nanocages can be precisely tuned into the near-infrared where the attenuation of light by blood and soft tissue is negligible. Thus, the optical properties of the Au nanocages can be considered for use in biomedical applications. Here, we highlight recent advances in the use of Au nanocages as both optical contrast enhancement and photothermal therapy agents. Our preliminary experiments indicate that Au nanocages do provide enhanced contrast when integrated with optical coherence tomography and can serve as photothermal transducers for the selective ablation of cancer cells. These results suggest that Au nanocages represent a new class of biocompatible nanostructures for cancer detection and treatment.
9:00 PM - PP3.8
Identification of Unamplified Genomic DNA Sequences by Plasmon Resonance on Gold Nanoparticles Using a Novel Thin Film Photodetector.
Rodrigo Martins 1 2 , Pedro Baptista 3 , Leonardo Silva 2 1 , Leandro Raniero 4 , Goncalo Doria 3 5 , Ricardo Franco 5 , Elvira Fortunato 2 1 Show Abstract
1 CEMOP, Uninova, Caparica Portugal, 2 CENIMAT I3N, FCTUNL, Caparica Portugal, 3 CIGMH/SABT, FCTUNL, Caparica Portugal, 4 INMetro, Inst. Nacional de Metrologia, Normalização e Qualidade Industrial , Rio de Janeiro Brazil, 5 REQUIMTE & Departamento de Química, FCTUNL, Caparica Portugal
Nowadays many clinical diagnostic applications require simple and inexpensive assays for detection and quantification of very small amounts of DNA. Standard nucleic acid diagnostics is dominated by fluorescence-based assays using complex and expensive enzyme-based target or signal-amplification procedures. Recently, several colorimetric detection methods for identifying nucleic acid based on the distance-dependent optical properties of gold nanoparticles have been reported, which involve the recognition of the specific target sequence by DNA-modified gold nanoparticle probes. We have developed a novel colorimetric method  enabling for detection of nucleic acid targets in a homogeneous format without target or signal amplification, with a highly improved sensitivity by means of a new optoelectronic detection platform based on an amorphous silicon thin film photodetector. This new optoelectronic detection platform permits the detection of at least 400 fentomole of specific DNA sequences, and was applied to the rapid detection of human pathogens in large variety of clinical samples such as Mycobacterium tuberculosis and of single point mutations (Beta-globin locus). The low cost auto-powered equipment together with its compatibility with microfluidic sample handling and its low complexity will be discussed, together with the optoelectronic performances of the platform developed.
9:00 PM - PP3.9
The Role of Competitive Ion Coordination in the Formation of Metal Nanoparticles Mediated by Block Copolymers.
Alessandro Napoli 1 , Cornelia Palivan 1 , Björn Niesen 1 , Wolfgang Meier 1 Show Abstract
1 Chemistry, University of Basel, Basel Switzerland
We have investigated the formation of gold nanoparticles mediated by amphiphilic block copolymers in water. Block copolymers of hydrophobic poly(propylene sulfide) (PPS) and hydrophilic poly(ethylene glycol) (PEG) form supramolecular aggregates such as vesicles and micelles and offer two distinct chemical moieties (R-S-R, R-O-R) for coordination to Aun+ ions and binding to metallic Au0. Different preparation methods and copolymer architectures have been investigated and characterized by TEM, UV-VIS and IR spectroscopy and coupled to electron spin resonance spectroscopy (ESR) on paramagnetic Cu2+ ions. In a common solvent (e.g. chloroform) the competition between thioethers and ethers is dictated mainly by equilibrium constants with the first favored over the second. In water, a solvent only for PEG, accessibility of thioethers and their oxidation by chloroaurate inverts the situation and different strategies have to be considered to obtain nanoparticles where thioethers act as stable ligands. The results highlight the ultimate role of metal ion complexation in determining the shape and size distribution of metallic clusters stabilized by heteroatom polymeric ligands.The coexistence of a polyether and a polythioether block poses a fundamental question: which atoms are involved in Au ionic species coordination (nucleation) and in the subsequent binding to Au0 clusters. As observed in other block copolymer systems based on polyethers, C-O-C moieties can coordinate Au ions and drive its disproportionation into metallic clusters. The higher affinity of C-S-C for Au ions is here limited in water by the hydrophobic character of the block. Thus the availability of S for gold binding strongly depends on the hydrophilic/lipophilic balance of the block copolymers affecting the aggregate morphology, curvature and critical micellar concentration (CMC), the latter indicating the concentration of non-aggregated copolymer chains. Moreover, it is known that in presence of water chloroaurate catalyzes the oxidation of thioethers into sulfoxides. We have observed such oxidation in certain copolymer architectures and exploited it for one-pot synthesis of gold nanoparticles.
Jinwoo Cheon Yonsei University
Hedi Mattoussi Naval Research Laboratory
Christof M. Niemeyer Universitaet Dortmund
Geoffrey Strouse Florida State University
PP4: Toxicity of and Sensing with Biocompatible Nanoparticles
Tuesday AM, November 27, 2007
Room 203 (Hynes)
9:30 AM - **PP4.1
Physico-chemical Properties of Quantum Dots and their Impact on Cells: the Janus Face of QDs.
Francoise Winnik 1 , Dusica Maysinger 2 Show Abstract
1 Chemistry, Universite de Montreal, Montreal , Quebec, Canada, 2 Pharmacology and Therapeutics, McGill University, Montréal, Quebec, Canada
Nanoparticles, such as luminescent quantum dots, ferrofluids, gold nanoparticles, and polymer micelles, are studied extensively as bioimaging tools for cells and whole organisms and as nano-containers for controlled and/or sustained drug delivery. The staggering variety of such nanoparticles in our environment and laboratories has become a cause for concern. Indeed, only a rather limited number of nanoparticles has actually been assessed in detail, either in vitro or in vivo, for evidence of biocompatibility and safety of use in the laboratory or in daily life. Clearly, there is a need to evaluate the potential threat that nanoparticles might pose to the organism. The overall objective of the work presented is to determine the impact of nanoparticles on cell functions, with a focus on metal nanoparticles, primarily quantum dots (QDs) and on their effects on live cells and animals. Special emphasis will be placed on QDs subcellular distribution, and on the effects of QDs on cellular organelles. Induction of cell death by nanoparticles is discussed in the context of the composition and physico-chemical properties of selected nanoparticles and of the cell status.
10:00 AM - PP4.2
Non-invasive Technique for Intracellular Delivery of Nanosensors into Stem Cells
Karen Fisher 1 2 , Jonathan Aylott 2 , Rhodri Jones 2 , Vesselin Paunov 1 Show Abstract
1 Department of Chemistry, University of Hull, Hull, North Humberside, United Kingdom, 2 School of Pharmacy and Department of Immunology, University of Nottingham, Nottingham United Kingdom
We report a new method for delivery of nanosensors through the membrane of living stem cells. The method is based on using cationic liposomes as encapsulating agents for nanosensors as their membranes naturally fuse with cellular membrane. This makes them prospective vehicles for intracellular delivery of nanosensor probes. Polyacrylamide nanosensor particles were prepared by water-in-oil microemulsion polymerisation where the monomers (acrylamide and N,N-methylene bisacrylamide) and fluorophores are dissolved in water and introduced to the microemulsion as the aqueous phase. The produced nanosensors are spherical polymeric particles with a typical diameter of 50 nm which results in sub-second response times, indeed some sensors respond in the millisecond timeframe. Nanosensors consist of a stimulus-responsive fluorescent probe encapsulated into a porous nanoparticle where the fluorophore and other components of the sensor cannot leak out and contaminate the cell interior, while the signal triggering component (analyte) can freely diffuse through the pores of the nanosensor matrix. Using this versatile methodology a range of pH and oxygen sensitive fluorophores were physically entrapped within the nanoparticles polymeric matrix by binding to high molecular weight dextran molecules. We used the lipid extrusion technique to encapsulate our nanosensor particles within the small liposomes doped with a cationic lipid. The nanosensor suspension was mixed with the cationic liposomes followed by multiple extrusions through a polycarbonate membrane. We used TEM to study the degree of encapsulation of the nanosensors inside the liposomes. We used human mesenchymal stem cells (hMSC) to test the nanosensor delivery method by exposing the cells to liposomes modified with fluorescently tagged lipids and cationic liposomes loaded with fluorescently labeled nanosensors. An increase in fluorescence of hMSC was seen following incubation with PC:PG:FITC DHPE liposomes. We also showed that the nanosensors are successfully delivered into the cell interior after incubation of the hMSC cells with nanosensor loaded liposomes which was confirmed by confocal fluorescence microscopy and other techniques. The developed new method for non-invasive intracellular delivery of nanosensors can find a number of applications for monitoring the local conditions inside cells for a number of cell types. Intracellular delivery of the nanosensors allows important metabolic markers (glucose, oxygen, calcium and pH) to be determined as hMSC differentiation occurs. This information can help to identify differentiation events and trigger the development of new classes of nanosensors to monitor and record the lineage commitments of hMSC.
10:15 AM - PP4.3
Investigation of Quantum Dot Induced Neurocytotoxicity UsingHigh Content Screening Assays.
Edward Jan 1 2 3 , Stephen Byrne 2 , Aine Whelan Whelan 2 , Yurii Gun ko 2 , Yuri Volkov 3 , Nicholas Kotov 1 Show Abstract
1 Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 School of Chemistry, Trinity College Dublin, Dublin Ireland, 3 Department of Clinical Medicine, Trinity College Dublin, Dublin Ireland
10:30 AM - PP4.4
An Atomistic Level Description of the Quantum Dot Organic Ligand Interface by Ab initio Calculations: Effect of Core Structure on Cytotoxicity.
Rodion Belosludov 1 , Hiroshi Mizuseki 1 , Atsuo Kasuya 2 , Yoshiyuki Kawazoe 1 Show Abstract
1 Institute for Materials Research, Tohoku University, Sendai, Miyagi, Japan, 2 Center for Interdisciplinary Research, Tohoku University, Sendai, Miyagi, Japan
Despite the remarkable progress in the photostability and bio-fictionalization of QDs, a large and important limitation of these nanomaterials still exists in their potential high cyclotoxicity [1, 2]. The common strategy for making QD bioconjugates includes both covering the semiconductor core structure by a shell of semiconductor material with a larger band gap followed by a bio cap using different functional molecules which improve the solubility of the QD and provide a specific target to anticancer agents. However, even in this case, cyclotoxicity, correlated with the liberation of free Cd2+ ions due to deterioration of the CdSe lattice, has been observed .The aim of this study is to gain an understanding of the structural morphology of the core as well as the inorganic/organic interface at the atomistic level using highly accurate first-principles calculations in an effort to improve upon the materials currently used in cancer diagnosis. Therefore, one solution to the cytotoxicity problem is to design and synthesize new nanocomposites that are more stable than currently used crystalline QDs. Using first-principles calculations, we have predicted the existence of (CdSe)n (n=33 and 34) nanoparticles of 1.45 nm in size, which were also identified by experiment. These nanoparticles do not adopt the crystal form of CdSe while resembling more closely carbon fullerenes and are remarkably stable . Using these configurations as initial structures, the new shell-core particles (ZnS)28/(CdSe)4 are found to be energetically stable and the outer cage structures based on ZnS are undistorted. We have also found a highly stable nanocluster (CdSe)61 with the same core/shell feature, allowing us to suggest the possibility of an experimental synthesis of fullerene-like structures with a diameter of approximately 2 nm.As a continuation, we investigated the effect of organic ligand binding on the stability of CdSe as well as CdSe/ZnS nanoparticles with both crystalline and fullerene-like structures. There are several ligands such as MAA, DTT, DHLA employed in these calculations. The results show that the interactions of these ligands with crystalline particles are stronger than with fullerene-like particles due to charge transfer between the organic ligand and the metal surface atoms. This leads to a strong distortion of the core surface and in some cases, to decomposition of the crystalline nanoparticle. Moreover, the full covering of QDs can be easily achieved in the case of nanoparticles in comparison to the crystalline forms. Our results indicate that decreasing the size of the imaging agent can possibly lead to biologically inert coverings, making it possible to avoid cellular toxicity. REFERENCES1.I. L. Medintz et al. Nature Materials 4, 435-446, 2005.2.X. Michalet et al. Science 307, 538-544, 2005.3.A.M. Derfus, W.C.W. Chan and S.N. Bhatia, Nano Lett. 4, 11-18, 2004.4.A. Kasuya et al., Nature Materials 3, 99-102, 2004.
10:45 AM - PP4.5
Fluorescence Detection of Proteolysis Using Quantum Dot-protein Substrates.
Aaron Clapp 1 , Igor Medintz 2 , Ellen Goldman 2 , Hedi Mattoussi 3 Show Abstract
1 Chemical & Biological Engineering, Iowa State University, Ames, Iowa, United States, 2 Center for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, District of Columbia, United States, 3 Optical Sciences Division, Naval Research Laboratory, Washington, District of Columbia, United States
Quantum dot (QD)-protein bioconjugates were used as substrates to detect protease activity in solution. This method is based on measurable changes in the fluorescence resonance energy transfer (FRET) efficiency between QDs and surface-bound dye-labeled protein substrates following enzymatic digestion. Using a standard Michaelis-Menten model, we determined values for the Michaelis constant and the maximum enzymatic velocity for several enzyme-substrate pairs. Mechanisms of enzymatic inhibition and inhibitor dissociation constants and were also inferred from the FRET data collected in the presence of inhibitors.
11:00 AM - PP4.6
Live Cell Imaging with Semiconductor and Magnetic Quantum Dots.
S. Tamil Selvan 1 , Alex Lin 1 , Pranab Patra 1 , Chung Yen Ang 1 , Georgia Papaefthymiou 2 , Jackie Ying 1 Show Abstract
1 , Insitute of Bioengineering & Nanotechnology, Singapore Singapore, 2 Department of Physics , Villanova University, Villanova, Pennsylvania, United States
This talk will describe a facile synthesis of a bi-functional nanocomposite system consisting of magnetic nanoparticles (Fe2O3) and semiconductor quantum dots (CdSe QDs) developed in our laboratory. The CdSe QDs were grown onto preformed Fe2O3 cores at a high temperature (300°C) in the presence of organic surfactants, yielding either heterodimers or homogeneous dispersion of QDs around the cores. The resulting magnetic quantum dots (MQDs) exhibited tunable emission properties, and superconducting quantum interference device (SQUID) data illustrated that the MQDs were superparamagnetic. The plain QDs and MQDs (without ZnS capping) were coated with thin layers of silica, and used for the labeling of different live cell membranes (HepG2 human liver cancer cells, NIH-3T3 mouse fibroblast cells, and 4T1 mouse breast cancer cells) through a simple bioconjugation method. 1. S. T. Selvan, P. K. Patra, C. Y. Ang and J. Y. Ying, “Synthesis of Silica-Coated Semiconductor and Magnetic Quantum Dots and Their Use in the Imaging of Live Cells,” Angew. Chem. Int. Ed. (2007), 46, 2448-2452. 2. D. K. Yi, S. T. Selvan, S. S. Lee, G. C. Papaefthymiou, D. Kundaliya and J. Y. Ying, “Silica-Coated Nanocomposites of Magnetic Nanoparticles and Quantum Dots,” J. Am. Chem. Soc. (2005), 127, 4990-4991. 3. S. T. Selvan, T. T. Tan and J. Y. Ying, “Robust, Non-Cytotoxic, Silica-Coated CdSe Quantum Dots with Efficient Photoluminescence,” Adv. Mater. (2005), 17, 1620-1625.
11:30 AM - **PP4.7
Nucleation of Alpha-Synuclein Aggregation in Live Cells by Quantum Dots.
Maria Roberti 1 2 , Thomas Jovin 2 , Elizabeth Jares-Erijman 1 Show Abstract
1 Organic Chemistry, University of Buenos Aires, Buenos Aires Argentina, 2 Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Goettingen Germany
We exploited the multivalency of streptavidin-conjugate QDs to assemble artificial nucleation centers that exert a biological impact on a cellular event of interest, namely the aggregation of alpha-synuclein (AS). AS is an abundant and natively unfolded pre-synaptic protein (14 kDa) involved in the pathogenesis of Parkinson’s disease, which is characterized by the formation of aberrant, amyloid-like deposits of this protein. There is growing evidence indicating that cytotoxicity of effect on motor neurons is due to the oligomerization of AS, and many efforts are devoted to decipher both the physiological function and the mechanisms underlying the pathological self-association of AS. In previous work1, we fused AS with a 12-aa peptide bearing a tetracysteine tag (CCPGCC) for binding fluorogenic biarsenical compounds (e.g. FlAsH, ReAsH). Extensive characterization of the recombinant protein (AS-C4) indicated that the biophysical, biochemical and aggregation properties matched those of the wild-type protein, in vitro and inside cells. We show here that AS-conjugated QDs can act as nucleation seeds that induce the aggregation of FlAsH-labeled AS-C4. We were able to track simultaneously the fate of both the nucleation seeds and the bulk protein through fluorescence spectroscopy and microscopy in vitro and inside cells (loaded by microinjection). We evaluated the ability of QDs as initiators for alpha-AS aggregation from two aspects: their effective concentration in the aggregation mixture, related to the probability of forming nucleation points, and the modulation effect of different AS-QD loading ratios.. Fluorescence imaging of amyloid formation in living cells by a functional, tetracysteine-tagged alpha–synuclein; MJ Roberti, CW Bertoncini, R Klement, EA Jares Erijman, and TM Jovin; Nature Methods 4, 345 - 351 (2007).
12:00 PM - PP4.8
Spectral Barcoding of Polystyrene Beads Using Multicolored Quantum Dots for High-Throughput Screening Applications.
Shyam Vaidya 1 , Lane Gilchrist 1 , Charles Maldarelli 1 , Alexander Couzis 1 Show Abstract
1 Chemical Engineering, City Collge of the City University of New York, New York, New York, United States
The focus of this presentation is the development of optically barcoded polymer beads for use in high-throughput, multiplexed screening applications such as protein microarrays or flow cytometry. Luminescent semiconductor nanocrystals (or quantum dots (QDs)) with different emission wavelengths (colors), and encapsulated in different compositions in polystyrene (PS) beads are used to define an optical barcode. The encapsulation is undertaken by copolymerizing the PS beads with hydrophobically capped, core-shell, CdSe/ZnS QDs, using a spraying suspension polymerization procedure. Liquid styrene monomer, containing a thermally activated free radical initiator and dispersed QDs in a prescribed composition, is sprayed as microdroplets (10-100 microns in diameter) into an aqueous solution. The microdroplets are then polymerized by heating, and the beads subsequently recovered. Confocal laser scanning microscopy (CLSM) images of the nanocrystal luminescence in the bead interior indicate that the QDs are segregated into inclusions distributed throughout the bead. CLSM and fluorimetry measurements of the emission spectra of PS beads embedded with three color QDs in varying concentrations are reported which verify that distinguishable optical barcodes derived from the spectral scans of these QD can be obtained by this technique. The emission spectra also indicate Forster Resonance Energy Transfer (FRET) from the lower wavelength to the higher wavelength emitting QDs, providing evidence that the QDs are situated within nanometers of each other in the inclusions. The addition of non-luminescent nanocrystals, such as silica or iron oxide, along with the QDs to separate the QDs from one another in the inclusions and reduce the energy transfer is also reported. We also report the assembly of the encoded beads onto a substrate surface as a microarray. Beads with an encapsulated iron oxide nanoparticle are spread into a monolayer on a substrate surface, and a magnetic field is applied underneath the surface to affix the microbeads to the substrate. The surface has been previously passivated with a polyethylene glycol oligomer to prevent nonspecific adsorption of biomolecules in an assay. This assembly is a prototype to host biological probes such as peptides, and antibodies. (In addition, by coating the beads with bilayers and sequestering membrane receptors in the bilayers, this platform can be used for the display of difficult to present membrane receptors which require a lipid environment to retain their biological binding ability.) In the bead-formatted microarray, binding of a target to a probe is detected in the usual manner for microarrays by the luminescence of a fluorescent label on the target. By reading the code on the bead lit by this label, the identity of the probe molecule binding the target can be obtained.
12:15 PM - PP4.9
Visualization and Sizing of Nano-particles in Liquid Solution Through the Independent yet Simultaneous Tracking of their Brownian Motion.
Andrew Malloy 1 , Bob Carr 1 Show Abstract
1 , NanoSight Ltd, Salisbury United Kingdom
A nanoparticle tracking analysis system is described which allows nanoscale particles in a suspension to be visualised (but not imaged) and simultaneously but individually sized with higher particle size distribution resolution than other light scattering techniques . Sample pre-treatment is minimal requiring only dilution with a suitable solvent to an acceptable concentration range (between 10^5 and 10^10 per ml depending on sample type). Accurate and reproducible analyses can be obtained from video of only a few seconds duration and the results allow particle number concentration to be recovered. Given the close to real-time nature of the technique, particle-particle interactions are accessible as is information about sample aggregation and dissemination. All particle types can be measured and in any solvent type providing that the particles scatter sufficient light to be visible (i.e. are not indexed matched). The minimum detectable size measurable depends on particle refractive index but can be as low as 10nm for high refractive index materials such as colloidal silver. The technique is robust and low cost representing an attractive alternative or complement to higher cost and more complex methods of nanoparticle analysis such as photon correlation spectroscopy or electron microscopy that are currently employed in a wide range of technical and scientific sectors. Finally, the technique uniquely allows the user a simple and direct qualitative view of the sample under analysis (perhaps to validate data obtained from other techniques such as PCS) and from which an independent quantitative estimation of sample size, size distribution and concentration can be immediately obtained.
12:30 PM - **PP4.10
Luminescent Lanthanide-ion Doped Nanoparticles as Single-Biomolecule Labels and Oxidant Sensors.
D. Casanova 1 , T. Nguyen 1 , D. Giaume 2 , G. Mialon 2 , M. Moreau 2 , T. Gacoin 2 , J. Boilot 2 , A. Alexandrou 1 Show Abstract
1 Laboratoire d'Optique et Biosciences , CNRS-INSERM, Palaiseau France, 2 Laboratoire de Physique de la Matiere Condensee, CNRS, Palaiseau France
We have recently demonstrated that lanthanide-ion doped oxide nanoparticles are an alternative class of biological fluorescent probes particularly attractive for single-molecule tracking applications . They are synthesized directly in water, present high photostability and no blinking, narrow emission linewidths independent of nanoparticle size, and long excited state lifetimes which are useful for retarded detection schemes  and FRET applications .In the case of Y0.6Eu0.4VO4 nanoparticles, we have demonstrated that the size of each nanoparticle can be calculated from its luminosity measured with optical microscopy . This is confirmed by the good agreement between the nanoparticle size distribution obtained from transmission electron microscopy measurements and the one calculated from luminosity histograms of individual nanoparticles. Small sizes down to 13 nm are detectable. Such an in situ size determination is important for assessing the perturbation of the biomolecule behavior induced by the nanoparticle label. After functionalization of these nanoparticles with guanidine or amine groups we can target sodium channels  or, more generally, amine and sulfhydryl groups on proteins, respectively. In addition, these nanoparticles are sensitive H2O2 detectors. We have shown that excitation of the nanoparticles at the 7F0,1-5D2 Eu3+ transition (466 nm) induces a reduction of Eu3+ ions to Eu2+ and a decrease of the nanoparticle luminosity at the 5D0-7F2 Eu3+ transition (617 nm). The presence of H2O2 induces the reverse process: oxidation of Eu2+ ions to Eu3+ and an increase of the nanoparticle luminosity at 617 nm. This luminescence recovery of single nanoparticles is remarkably linear with H2O2 concentration in a very broad range from 1 µM to 500 µM. Single Y0.6Eu0.4VO4 nanoparticles can thus be used as local, quantitative H2O2 sensors. The reversibility of the Eu2+ oxidation opens the possibility of following time-dependent H2O2 concentrations involved in various cell processes. Lanthanide-doped nanoparticles are therefore bifunctional labels allowing simultaneous biomolecule tracking and H2O2 sensing. E. Beaurepaire, V. Buissette, M.-P. Sauviat, D. Giaume, K. Lahlil, A. Mercuri, D. Casanova, A. Huignard, J.-L. Martin, T. Gacoin, J.-P. Boilot, A. Alexandrou, Nano Lett. 4, 2079 (2004).  D. Casanova, D. Giaume, T. Gacoin, J.-P. Boilot, A. Alexandrou, J. Phys. Chem. B. 110, 19264 (2006). D. Casanova, D. Giaume, E. Beaurepaire, T. Gacoin, J.-P. Boilot, A. Alexandrou, Appl. Phys. Lett. 89, 253103 (2006).
PP5: Nanoparticle-Nanoparticle and Nanoparticle-Bioreceptor Interactions
A. Paul Alivisatos
Tuesday PM, November 27, 2007
Room 203 (Hynes)
2:30 PM - **PP5.1
Plasmon Rulers for Measuring Dynamical Distance Changes in Biological Macromolecular Assemblies.
Paul Alivisatos 1 Show Abstract
1 Materials Sciences, Univ of CA-Berkeley, Berkeley, California, United States
The intensity and spectral signature of light scattering from Au nanocrystals depends strongly upon their separation. This phenomenon can be used to construct a spectroscopic ruler for monitoring the assembly and deformations of macromolecular complexes. More advanced arrangements consisting of groups of several nanocrystals are also under construction.
3:00 PM - PP5.2
Direct Attachment of Recombinant Poly-histidine Tag Proteins to Gold Nanoparticles.
Joshua Kogot 1 , Timothy Logan 1 2 , Geoffrey Strouse 1 Show Abstract
1 Dept. of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida, United States, 2 , Institute of Molecular Biophysics, Tallahassee, Florida, United States
The interface of biology and nanomaterials provides a mechanism for the further development of molecular beacons, drug delivery agents, optical sensors, and elucidation of biomolecule structures. Hence, a critical understanding about any perturbing effects that nanoparticles may have on the “normal” structure and function of biomolecules is necessary. A protein with an N-terminal poly-histidine tag is bound to the surface of a sub-2nm gold nanoparticle to understand the effect on biomolecule structure and function. Using techniques such as NMR, fluorescence, absorbance, and CD spectroscopy it is possible to determine changes in protein structure and loss of functionality due to direct attachment of the biomolecules to the gold nanoparticle surface. Biophysical methods such as CD spectroscopy and 2D-NMR are used to monitor global and local structure changes to the His-tag protein during incubation with the gold nanoparticles. Fluorescence spectroscopy and 2D-NMR both provide evidence for a single, covalent attachment of the protein to the gold nanoparticles. Protein functional studies by direct ligand binding, and the absence of widespread 2D-NMR chemical shift perturbations with the gold nanoparticles, suggests little or no loss in function upon incubation. Overall, protein binding to gold nanoparticles via a poly-histidine tag provides a useful bio-nano assembly mechanism for an effective covalent attachment using a common recombinant protein modification.
3:15 PM - PP5.3
Kinetics of Metal-Affinity Driven Self-Assembly between Proteins/Peptides and CdSe-ZnS Quantum Dots.
Kim Sapsford 1 , Thomas Pons 1 , Igor Medintz 1 , Florence Brunel 2 , S. Higashiya 3 , Philip Dawson 2 , Hedi Mattoussi 1 Show Abstract
1 Optical Sciences Division and Center for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, District of Columbia, United States, 2 Departments of Cell Biology & Chemistry and the Skaggs Institute of Chemical Biology, The Scripps Research Institute, La Jolla, California, United States, 3 Department of Chemistry, SUNY Albany, Albany , New York, United States
3:30 PM - **PP5.4
Multifunctional Nanoparticles for Dual Mode Imaging and Therapy.
Kimberly Hamad-Schifferli 1 Show Abstract
1 Biological and Mechanical Engineering, MIT, Cambridge, Massachusetts, United States
Multifunctional particles have generated a great deal of interest for disease therapy. A single particle that has the multiple functions of targeting a specific site, can be imaged by one or more means, and deliver drugs or treatments would impart new capabilities in disease treatment. We describe an approach toward multifunctional nanoparticles using use sub-nanometer metallic clusters encapsulated in dendrimers. The cluster possesses unique physical properties which can be exploited for imaging by both magnetic relaxation (MR) and fluorescence microscopy. This allows imaging on two lengthscales, the macroscopic and the molecular. Furthermore, the encapsulating dendrimer imparts enhanced biological properties such as cellular uptake and low cytotoxicity. The dendrimer endgroups can be chemically modified with targeting moieties such as peptides or antibodies, and the overall molecule can package DNA for gene delivery. Synthesis, physical characterization, and imaging of the clusters will be discussed, along with preliminary work in biological applications. In addition, will discuss how we are exploring how to link nanoparticles to biomolecules without negatively impacting the linked biomolecules. By probing the structure of the protein when linked to a particle, we are gaining an understanding of how to optimally achieve conjugation, and thus are constructing design rulesfor nanoparticle interfaces to biological systems.
4:30 PM - **PP5.5
Core-Shell Silica Nanoparticles as Fluorescent Labels and Sensors for Bioimaging: C Dots.
Ulrich Wiesner 1 Show Abstract
1 , Cornell University, Ithaca, New York, United States
5:00 PM - PP5.6
``Adenovirus-Magnet" Hybrid Nanoparticle for Magnetic Resonance Imaging of Target Specific Gene Delivery.
Jae-Hyun Lee 1 , Young-wook Jun 1 , Jinwoo Cheon 1 Show Abstract
1 Chemistry, Yonsei University , Seoul Korea (the Republic of)
5:15 PM - PP5.7
Structural Studies of Covalent Site-specific Nanoparticle-Cytochrome C Conjugates.
Marie-Eve Aubin-Tam 1 , Kimberly Hamad-Schifferli 2 1 Show Abstract
1 Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Nanoparticle-protein conjugates have broad range of applications in biological sensing, imaging, assembly, delivery and control of enzyme activity. Covalent site-specific labeling is highly desirable because protein orientation can be controlled, and bioconjugate stability could be maintained over a wide range of ionic strength and pH. It also enables choosing labeling sites that will not interfere with the protein structure and function. However, site-specific covalent labeling remains a challenge because of multiple possible interactions at the interface between proteins and nanoparticles. Furthermore, those non-specific interactions are likely to distort the protein structure.We report site-specific covalent labeling of Yeast cytochrome c with Au and CoFe2O4 nanoparticles via a specific surface cysteine. The site of attachment can be controlled by using mutants of cytochrome c having a single cysteine at various positions on the surface of the protein. The protein structure is characterized with circular dichroism spectroscopy and redox properties by optical absorption. As a control for non-specific attachment, we link Horse Cytochrome c to nanoparticles via electrostatic adsorption. We find that the nanoparticle surface chemistry, the nanoparticle material, the nature of the protein-nanoparticle linkage, and the position of the labeled site have significant effects on the structure of nanoparticle-cytochrome c complexes[1,2]. This behavior can be rationalized by considering interactions between the nanoparticle and amino acids in the vicinity of the labeled cysteine. Molecular dynamics simulations of nanoparticle-protein conjugates are providing more detail on the source of structural disturbance as a function of the nanoparticle labeling positions.These results are significant for applications which utilize proteins adsorbed on surfaces or nanostructures. We find that for improved activity of proteins, particular caution should be taken to impede strong non-specific bonding between the protein side-chains and the nanoparticles. M.-E. Aubin-Tam and K. Hamad-Schifferli, "Gold nanoparticle-cytochrome c complexes: the effect of nanoparticle ligand charge on protein structure" Langmuir, 2005, 21, 12080 - 12084. M.-E. Aubin-Tam, H. Zhou, and K. Hamad-Schifferli, "Site specific labeling of cytochrome c with magnetic nanoparticles," 2007, submitted.
5:30 PM - PP5.8
Correlation of Collagen Receptor Distribution and Extracellular Matrix Deformation Using Gold Nanorods.
Sarah Baxter 1 , Katherine Langley 4 , John Stone 3 , Nidhi Kumar 2 , Mary Morales 2 , Christopher Robinson 5 , Catherine Murphy 3 , Edie Goldsmith 2 Show Abstract
1 Mechanical Engineering, University of South Carolina, Columbia, South Carolina, United States, 4 Biomedical Engineering, University of South Carolina, Columbia, South Carolina, United States, 3 Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina, United States, 2 Cell and Developmental Biology and Anatomy, University of South Carolina, Columbia, South Carolina, United States, 5 USC NanoCenter, University of South Carolina, Columbia, South Carolina, United States
It has been well-established that cellular response to mechanical environment is critical to cell/tissue function. In particular cell surface receptors, which directly connect cells to their surrounding extracellular matrix(ECM), facilitate the translation of mechanical tension outside the cell into biochemical signals and reactions within the cell. Subtle variations in the local mechanical environment, between cells and ne