Joerg Lahann University of Michigan
StevenR. Little University of Pittsburgh
Samir Mitragotri University of California-Santa Barbara
Matthew Tirrell University of California, Berkeley
Wednesday PM, April 27, 2011
Salons 10-11 (Marriott)
9:30 AM - LL1.1
Intracellular Drug Delivery Using Polymer Nano-needles.
Samir Mitragotri 1 2 , Poornima Kolhar 1 , Nishit Doshi 2 Show Abstract
1 Chemical Engineering Department, University of California, Santa Barbara, Santa Barbara, California, United States, 2 Biomolecular Science and Engineering, University of California, Santa Barbara, Santa Barbara, California, United States
Delivery of drugs into the cellular cytoplasm of target cells represents a major hurdle in treating various diseases, especially when the drug is an siRNA. This challenge can be addressed by encapsulation of cargos in nanoparticles, which can bind to diseased cells and get internalized. However, nanoparticles are typically internalized by cells via endocytosis and are subsequently sequestered in the lysosomes. Various methods have been proposed to enhance the escape of nanoparticles or their cargos from the endosome into the cytoplasm; however, such strategies have yielded mixed results, thereby limiting the effectiveness of the drug. Here, we address this limitation by engineering the shape of nanoparticles into a needle-like form. In this study we utilized needle shaped polystyrene particles fabricated by the film stretching process. We observed that needle-shaped particles exhibit substantially higher cytoplasmic drug delivery compared to their spherical counterparts. Needles caused a higher delivery of siRNA and led to 3 fold higher gene knockdown compared to spherical particles in GFP-expressing endothelial cells. We found that the aspect ratio and the surface modification of the particles influenced the knockdown caused by the particles. Mechanistic studies showed that spherical particles relied only on endocytosis for intracellular delivery, while needle-shaped particles, in addition to endocytosis, induced direct cytoplasmic delivery by permeabilization of the cell membrane. Needles synthesized using PLGA polymer also exhibited a similar knockdown revealing that the knockdown is related to the shape of the particles and not the polymer used. Nano-needles can be functionalized to induce selective permeabilization of target cells. With further research focused on safety and efficacy, these needles may open new opportunities in delivering siRNA and other drugs into cells.
9:45 AM - LL1.2
Micro- and Nanoparticles with Multiple Compartments.
Joerg Lahann 1 Show Abstract
1 Chemical Engineering, Materials Science and Engineering, Macromolecular Science and Engineering and Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States
Compartmentalized particles enable co-presentation of orthogonal sets of properties, thereby offering a broad design space for multifunctional particles. Electrohydrodynamic co-jetting is a simple, yet versatile fabrication technique that can be used to prepare multicompartmental particles. Because particles can be comprised of distinct polymers in different compartments, selective surface modification becomes possible. The latter can result in unidirectional interactions with cells or for colloidal self-assembly. Alternatively, multicompartmental particles may offer new routes towards targeted drug delivery.
10:00 AM - LL1.3
Controlled Degradation of Janus Particles.
Sangyeul Hwang 1 , Joerg Lahann 1 2 3 Show Abstract
1 Chemical Engineering, U of Michigan, Ann Arbor, Michigan, United States, 2 Biomedical Engineering, U of Michigan, Ann Arbor, Michigan, United States, 3 Materials Science and Engineering, U of Michigan, Ann Arbor, Michigan, United States
Unique architectures of anisotropic particles having two or more micro/nano-sized compartments and/or surfaces with different morphology, size, material, and/or chemistry shed light on various fields such as self-assembly, sensor, and catalysis. Some recent studies for such new class of colloidal materials include self-assemblies of magnetic Janus particles, regio-specific chemical modification and cell binding of bicompartmental particles, self-propulsion of surface-coated Janus particle via a site-specific reaction, emulsifier based on amphiphillic particle, and etc. Another potential usefulness of Janus particles is in area of drug delivery. Even though the reported research is rare, interest and demanding are highly arising, which encourage us to develop bicompartmental particles that can make use of controlling drug release.To achieve this goal, a designed particle can have asymmetric chemical properties in two different compartments, enabling to discriminate degradation rates of two compartments. One of plausible ideas to construct such anisotropic particle is to introduce non-equivalent chemical solubility, stability, and/or reactivity of each compartment. On condition that two different drugs can be respectively and locally loaded in two compartments of the same particle, and one of compartments is readily water soluble while the other is relatively slow, then releasing rates of two drugs in the particle would be controlled by the degradation rates of two different polymeric compartments. Herein, we report anisotropic particles with different compartments that can differentially degradable because of distinguishable crosslinking densities of two compartments in the particles. In this study, electrohydrodynamic co-jetting is employed to create a bicompartmental particle comprising interpenetrating polymer networks in which each compartment has different amount ratio of a chemically crosslinkable polymer (poly(acrylic amide-co-acrylic acid), water-soluble molecule partially interlaced in the network (poly(ethylene oxide)), and two different fluorophores as drug models (fluoroscein isocyante-dextran and rhodamine B isocyanate-dextran).
10:15 AM - LL1.4
Self-assembled, Mixed Micelles Composed Of PEG-lipids And Cytotoxic Peptide Amphiphiles For Cancer Therapy.
Matthew Tirrell 1 2 , Matthew Black 1 Show Abstract
1 Department of Bioengineering, University of California, Berkeley, Berkeley, California, United States, 2 Department of Chemical Engineering, University of California, Berkeley, Berkeley, California, United States
Peptides have enormous potential as therapeutic agents due to their ease of rational design and target specificity, but they are limited by low stability and their ability to reach their desired target. Nanoparticles have the potential to overcome these limitations by protecting the peptides during circulation and delivering them to their disease targets. Peptide amphiphiles consist of a biofunctional peptide as the hydrophilic head group and either a single-chain fatty acid or a double-chain lipid as the hydrophobic group, often separated by a polyethylene glycol (PEG) or other spacer to drive self-assembly in aqueous solutions. The resulting micelles display a high density of functional peptides. Mixing different monomers leads to multifunctional mixed micelles with precise control over number and ratio of functionalities without the need for orthogonal chemical reactions. Therefore, multiple therapeutic, targeting, or internalizing peptides can be easily incorporated into the same nanostructure. The membrane disrupting peptide D-(KLAKLAK)2 was utilized as a therapeutic anti-cancer peptide and conjugated directly to a diC16 hydrophobic tail. The resulting peptide amphiphile self assembled into micelles and disrupted the outer membranes of cancer cells within minutes, resulting in necrotic cell death. The peptide amphiphile was mixed with PEG-lipids to form mixed micelles. The mixed micelles had significantly decreased cytotoxicity if the micelles were washed out over short time periods while the cytotoxicity of the peptide amphiphile alone was unaffected, indicating that the PEG was able to shield the anti-cancer peptide amphiphile. However, as the mixed micelles slowly disassembled over 24 hours, the peptide amphiphile regained its cytotoxicity. The slow disassembly allowed the peptide amphiphile to enter cancer cells and initiate apoptosis by disrupting the mitochondrial membranes. This work demonstrates that therapeutic peptides can be incorporated into self-assembled micelles with PEG-lipids and that the way peptides are displayed to cancer cells in nanoparticles can alter their potency and mode of action. Previous work has demonstrated that micelles constructed from peptide-PEG-lipids can deliver imaging agents to cancer in vivo. Future work will include targeting peptides at the end of the PEG chains to specifically deliver these therapeutic peptides to cancer in vivo. This platform has the potential to deliver not only D-(KLAKLAK)2 as a therapeutic to many types of cancers, but also provide a blueprint for an effective way to deliver a wide variety of peptide therapeutics to their disease targets.
10:30 AM - LL1.5
Interrogating the Biotic/Abiotic Interface to Control the Activity of Bio-inspired Nanocatalysts.
Marc Knecht 1 , Ryan Coppage 1 , Dennis Pacardo 1 , Joseph Slocik 2 , Rajesh Naik 2 Show Abstract
1 Chemistry, University of Kentucky, Lexington, Kentucky, United States, 2 , Air Force Research Lab, Wright-Patterson Air Force Base, Ohio, United States
Bio-inspired approaches represent new avenues towards multifunctional materials that employ biomimetic conditions to minimize energy and environmental impacts. While biocombinatorial pathways have isolated peptides with the ability to fabricate specific nanomaterials compositions, the interactions at the bio/nano interface remain poorly understood. This region mediates the activity and could be used to enhance functionality, thus it is important to elucidate these biomolecular surface interactions. In this talk, a description of these interactions will be discussed for biomimetic Pd nanocatalysts. Using peptides, Pd nanoparticles are fabricated that drive C-coupling reactions under energy efficient and eco-friendly conditions employing low catalyst concentrations. The effect of the peptide surface was assessed by using modified peptide sequences that demonstrate a >two-fold enhancement in activity for a single residue substitution. These results indicate that bio-inspired materials may possess desired activity for future catalyst materials where the peptide surface can be tuned to enhance stability and reactivity.
10:45 AM - LL1.6
Robust Plasma Polymerized-Titania/Silica Janus Microparticles.
Kyle Anderson 1 , Rachel Jakubiak 2 , Rajesh Naik 2 , Timothy Bunning 2 , Vladimir Tsukruk 1 Show Abstract
1 Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 Materials and Manufacturing Directorate, Air Force Research Laboratory, Dayton, Ohio, United States
Janus microparticles can be fabricated from a wide variety of organic and inorganic components. The Janus particle fabrication method employed in this study utilizes two basic steps: partially embedding solid, inorganic micro particles in a masking layer which is readily dissolvable followed by the deposition of a highly crosslinked plasma polymerized nanocoating on the top of the particles via plasma enhanced chemical vapor deposition (PEVCD). Different organic, functionalizing, responsive, and biomolecular materials ranging from acrylic compounds to organometallic molecules and aminoacids were deposited on silica and titania microsphere surfaces. To ensure that only a fraction of the total particle surface area is covered by the plasma polymer the microparticles are embedded into a protective polystyrene film which is removable after the plasma coating is applied. This facile, fast, and scalable selective polymerization approach allows for one-face polymerization, generating functionalized organic-inorganic Janus particles which are robust and can be further converted into a variety of interesting structures. Once created, the coatings can serve as templates for further modification including half-fluorescent, half-metal decorated and half-shelled structures. These can then be applied to an array of applications requiring partially functionalized or anisotropic geometries.
11:30 AM - **LL1.7
Magnetic Particle Imaging: A Novel Medical Imaging Method that Employs Safe, Magnetic Nanoparticle Contrast Agents.
Steven Conolly 1 , Patrick Goodwill 1 , Laura Croft 1 , Justin Konkle 1 , Kuan Lu 1 , Emine Saritas 1 , Arbi Tamrazian 1 , Bo Zheng 1 Show Abstract
1 Bioengineering & EECS, UC Berkeley, Berkeley , California, United States
Introduction: Magnetic Particle Imaging (MPI) [1,2,3] is a novel imaging modality that directly detects Ultra-Small Super-Paramagnetic Iron Oxide nanoparticle tracers (5 to 40 nm core diameter USPIO's) in the body. It has great promise as a safe, noninvasive, nonionizing and high-contrast replacement for the tens of millions of high-risk X-ray and CT diagnostic angiography studies performed annually. Iodinated contrast agents pose significant risk for Chronic Kidney Disease (CKD) patients. Fully 47% of Americans over 70 have CKD. Late-stage CKD patients have very high risk (30-40%) of losing kidney function from a single iodinated contrast injection. Yet tens of millions of CKD patients undergo high-risk iodinated X-ray studies each year, because there is no safer alternative. The MRI agent, Gadolinium, is also unsafe for CKD patients. By comparison, USPIO nanoparticle contrast agents are completely safe for CKD patients. Indeed, USPIOs are now FDA approved to treat anemia in late-stage CKD patients. MPI Technique: The new imaging modality Magnetic Particle Imaging (MPI) uses safe USPIO contrast agents and no ionizing radiation. MPI could be a breakthrough in safe angiography for CKD patients. USPIOs are mapped within the body by the inductive response to a low-frequency (2 to 25 kHz) RF magnetic field. The emitted induction signal gives us a quantitative measure of iron oxide located at the center of a strong (6500 mT/m) magnetic field gradient. All MPI magnets have relaxed (5%) field tolerances, so MPI scanners are far simpler to build than MRI, which requires ultra-precision (1 ppm) magnets. The magnetization in a USPIO's saturates at 600 mT, which is about 20 million times stronger than that detected in clinical MRI. Our Berkeley MPI scanner currently detects 70 nanograms of USPIO, equivalent to 1 mM venous concentration in a human. Hardware improvements could improve sensitivity to below 10 micromolar, enabling safe venous-injection angiography. The contrast of MPI is unprecedented since there is absolutely no signal from background tissue and there is no signal attenuation with depth. Current spatial resolution is about 2 mm; but significant improvement is expected.The Promise of New Nanoparticles: Resolution and SNR in MPI are strongly related to the magnetic properties of the USPIOs. New nanoparticles tailored for MPI could dramatically improve resolution (perhaps 10-fold). Moreover, it is eminently feasible to create UPSIOs that are biologically targeted (e.g., atherosclerosis, inflammation, cancer, etc) to create a truly functional imaging and angiography modality that is completely safe for CKD patients.References:  B. Gleich and J. Weizenecker. Nature, 435:1214, 2005. J. Rahmer, J. Weizenecker, B. Gleich, and J. Borgert, BMC Med. Imaging, 9(1) 2009. P. Goodwill and S. Conolly. IEEE Trans Med Imaging, 29(11), 2010.
12:00 PM - LL1.8
Anisotropic, Patchy Microspheres with Soft Protein Islets.
Steven Little 1 2 Show Abstract
1 Chemical Engineering, Bioengineering, and Immunology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 2 , The McGowan Institute for Regenerative Medicine, Pittsburgh, Pennsylvania, United States
Surface anisotropy (i.e. uniform patterns of discrete functional moieties), is a common feature of many natural systems and a hallmark of functional efficiency. Specifically, a given discrete unit, with anisotropy of chemical or physical properties (e.g. adhesion, repulsion, enzymatic reactivity, energy conservation or transfer) will endow function through regular short-range variability, leading to the possibility for longer-range “orderliness”. Examples include (but are not limited to) atoms in the “functional” groups of a molecule, proteins such as enzymes, and even the biological signatures of “patchiness” on cell surfaces during tissue organization and immune responses. For these reasons, discrete, synthetic building blocks that mimic anisotropy seen in nature could increase efficiency in the areas of sensors, opto-electronic devices, modulators, and drug delivery systems. Here, we report a new and robust technique to produce ordered patches around microspheres via combination of solid and liquid-phase deposition. The solid component of this new technique employs the microspheres themselves in proximity to its neighbors to determine the resulting pattern. The organization of the particles with respect to one another may be as simple as particle doublets (one contact point between particles) to lines of particles (2 contact points per particle 180 degrees on opposite poles), to more complex formations that lead to any number of contact points between solid microspheres. The liquid phase component of the processing technique takes advantage of surface tension and dewetting such that solutions of masking material may be localized only to the contact points between microspheres. Any number of patch materials can be used including various polymers and even precipitated sugars, salts and even lipids. We have also recently demonstrated the ability to spontaneously form various microstructures with these anisotropic particles using a ratio of particles with various numbers of patches of biotin using a streptavidin trigger.
12:15 PM - LL1.9
Charged Lipid Cubic Phase Nanogyroids for Molecular Encapsulation.
Cecilia Leal 1 , Nathan Bouxsein 1 , Kai Ewert 1 , Cyrus Safinya 1 Show Abstract
1 Materials Research Laboratory, University of California Santa Barbara, Santa Barbara, California, United States
The controlled transport of chemical solutes to cellular targets generally requires a suitable encapsulation system. One example is the delivery of exogenous nucleic acids into host cells using synthetic or viral carriers. Synthetic cationic lipid (CL) assemblies can efficiently be used for transfer of DNA into cells and more recently we found that the same assemblies can be used to deliver Small interfering RNAs (siRNAs) . siRNAs are short (19-29bp) double stranded nucleic acids that efficiently mediate gene knockdown in mammalian cells. We prepared a charged, 3D ordered CL-siRNA complex fluid system of bicontinuous cubic symmetry in a regime of low CL content . The structures were characterized by Synchrotron X-ray Scattering and the lipid matrix is a double gyroid consisting of periodic nanochannels (mediated by a lipid bilayer) with lattice size dimensions that can be modulated by water content, ranging from 100-200 Å. The incorporation of short nucleic acid molecules such as siRNA can be performed without disruption of the cubic phase. These supramolecular materials can serve as carriers for various drugs, as well as templates for inorganic nanostructures growth. The ability of CL siRNA aggregates to silence genes is strongly correlated with the amount of CL in the complex. Specifically, the number of CL per siRNA must be sufficiently large to pack the nucleic acid while remaining below a limit that induces cell toxicity. The bicontinuous cubic phase consists of membranes with positive Gaussian modulus that readily enhance the formation of transient pores. This fact becomes of major importance for intracellular drug delivery where the main requirement is fusion events between the lipid carrier and the endosomal membrane. The charged nanogyroid siRNA complex was prepared at low CL content and displays minor cytotoxicity and highly specific gene silencing activities.Funding provided by NIH GM-59288, DOE-BES-DE-FG-02-06ER46314 (self-assembly/structure studies), and NSF DMR-0803103.  Bouxsein et al. Biochemistry (2007) 46, 4785. Leal et al. JACS (2010) in press.
12:30 PM - LL1.10
Multicomponent Particle Preparation Using Peptide-controlled Fusion.
Hana Robson Marsden 1 , Itsuro Tomatsu 1 , Alexander Kros 1 Show Abstract
1 Leiden Institute of Chemistry, Leiden University, Leiden Netherlands
Membrane fusion has an overarching influence in living organisms. The fusion of sperm and egg membranes initiates the life of a sexually reproducing organism. Intracellular membrane fusion facilitates molecular trafficking within every cell of the organism during its entire lifetime, and virus-cell membrane fusion may signal the end of the organism’s life. Considering its importance, surprisingly little is known about the molecular-level mechanism of membrane fusion. Due to the complexity of a living cell, observations often leave room for ambiguity in interpretation. Therefore we recently developed an artificial model system composed of two complementary lipidated peptides to increase our understanding of controlled fusion processes between liposomes.(1,2) In both the life sciences and bioengineering, controlled membrane fusion has many possible applications, for example in drug delivery, gene transfer or chemical microreactors. In recent years the field of microreactor technology has drawn serious attention as a way to improve many organic synthesis methods with regards to increased yields and reduction of waste compared to traditional methods. Rapid mixing and efficient heat transfer allow the use of highly concentrated reagents thereby minimizing waste. Vesicles have been used as mini-laboratories to study confined chemical reactions, sometimes under biologically relevant conditions. The drawback so far is that the reagents have had to be premixed before the vesicles are assembled. The current state of the art in the field of controlled fusion between vesicles(1) now opens up the possibility to add and mix the content of different vesicles, expanding the scope of nanoreactor based applications. Thus, controlled vesicle fusion has the potential to be used as a fast, cheap and elegant alternative for complex microfluidic reactions in aqueous solutions.Current research in our group is aimed at utilizing this pair of coiled-coil peptides(1,2) to prepare multicomponent systems in which we control the interaction of liposomes with other nanosized objects (e.g. polymersomes(3), soft hydrogels, silica nanoparticles) resulting in multicomponent particles.References:1: H. Robson Marsden, N.A. Elbers, P.H.H. Bomans, N.A.J.M. Sommerdijk, and A. Kros. A Reduced SNARE Model for Membrane Fusion. Angewandte Chemie Int. Ed. 2009, 48, 2330–2333.2: H. Robson Marsden and A. Kros. Coiled coil self-assembly in synthetic-biology space: inspiration and progress. Angewandte Chemie Int. Ed. 2010, 49, 2988-3005.3: H. Robson-Marsden, J.W. Handgraaf, N.A.J.M. Sommerdijk, A. Kros. Combining Solid-Phase Peptide Synthesis with Ring Opening Polymerization: Synthesis and Self-Assembly of Poly(γ-benzyl L-glutamate)-block-Coiled Coil Peptide Copolymers, J. Am. Chem. Soc. 2010, 132, 2370–2377.
LL2: Biomimetic Particles and Drug Delivery
Wednesday PM, April 27, 2011
Salons 10-11 (Marriott)
2:30 PM - **LL2.1
Engineering Vesicles for Vaccines and Immunotherapy.
Darrell Irvine 1 2 Show Abstract
1 Materials Science & Engineering/Biol. Engineering, MIT, Cambridge, Massachusetts, United States, 2 , Howard Hughes Medical Institute, Chevy Chase, Maryland, United States
Lipid vesicles have long been of interest for drug and vaccine delivery, but liposomes generally have relatively poor stability in serum and their simple structure leaves limited room for engineering their properties. To gain access to a broader range of chemical and physical properties, we recently devised Interbilayer-Crosslinked Multilamellar Vesicles, or ICMVs. These lipid-based capsules are formed by synthesizing multilamellar liposomes, stabilized by the introduction of covalent crosslinks connecting tightly stacked lipids bilayer-to-bilayer within the vesicle walls. Using an aqueous self-assembly and chemical reaction-driven process, we show how these capsules enable the efficient loading and retention of both hydrophilic protein antigens (in the aqueous core) and lipophilic molecular adjuvants (in the vesicle walls). By sequestering both adjuvant and antigen molecules within the particle structure in this way, we found that these lipid particles form an extremely potent vaccine for both humoral and cellular immunity, eliciting up to ~30% antigen-specific CD8+ T-cells for a single epitope and strong IgG responses in mice. Notably, unlike live vaccine vectors that often must be used in so-called “heterologous” prime-boosting regimens due to anti-vector immunity, this pathogen-mimetic nanoparticle vaccine could be repeatedly administered, boosting both CD8+ T-cell and antibody responses on each immunization. In addition, these particles show promise as carriers of recombinant proteins for cancer immunotherapy, and application of ICMVs as carriers for adjuvant drugs in adoptive T-cell therapy of cancer will be briefly described.
3:00 PM - **LL2.2
Biodistribution of Shape and Size Specific Nanoparticles.
Kevin Herlihy 1 , Jillian Perry 1 2 , Marc Kai 3 , Joseph DeSimone 1 2 3 Show Abstract
1 Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States, 2 Lineberger Comprehensive Cancer Center, University of North Carolina , Chapel Hill, North Carolina, United States, 3 Chemical Engineering, North Carolina State University, Raleigh, North Carolina, United States
Nanoparticles have recently gained much momentum as therapeutic agents for cancer. Many researchers have turned to nanoparticles as a solution to deliver drugs with poor solubility or low therapeutic indexes. Nanoparticles also have the ability to alter a biodistribution of a drug. Particle size and shape has been shown to play an important role in biodistribution especially when particles have similar shapes to those found in nature. Herein a top-down particle fabrication technique called Particle Replication In Non-wetting Templates (PRINT®) is used to fabricate unique biocompatible particles in a number of highly tailored shapes and sizes. Particle surfaces were heavily modified with PEG in order to retard the rapid elimination by the Reticuloendothelial System (RES). Particles have been radiolabelled with 64Cu and biodistribution has been mapped as a function of particle shape and size using Positron Emission Tomography (PET). This work should help pave the way towards rational design of target-specific drug delivery through the manipulation of particle shape and size.
3:30 PM - LL2.3
Photonic Bandgap Mixing through a Magnetic Self-assembly of Superparamagnetic Nanocrystal Clusters for Structural Color Mixing.
Hyoki Kim 1 , Eun-Geun Kim 1 , Sung-Eun Choi 1 , Lily Nari Kim 1 , Sunghoon Kwon 1 Show Abstract
1 Electrical Engineering and Computer Science, Seoul National University, Seoul Korea (the Republic of)
In the wings of a butterfly or feathers of a peacock, structural color can be seen from the interaction of light with sub-wavelength structures. A certain wavelength of light cannot travel into such structures, thus corresponding wavelength of light can be seen as a color. Unlike chemical pigments, structural color shows iridescent and metallic color, and also it does not suffer from photo-bleaching as time passes. Due to its unique characteristics, many techniques to fabricate artificial structural color have been reported. However, for the wide use of structural color in various application areas, the basic feature that has to be incorporated might be the capability of broadening the color expression range through color mixing. While color mixing of chemical pigment can be easily achieved by simple mix of multiple color dyes or pigments with different absorption bands, but mix of the structural colors with different photonic band gaps is challenging through conventional fabrication techniques since it requires sophisticated manipulation of nanoscale building blocks. Here, we present novel structural color mixing technique through vertically aligned different photonic bandgap structures using a material whose photonic bandgap can be magnetically tunable and photochemically fixable. The material used for the work is M-Ink, which is three phase system composed of superparamagnetic colloidal nanocrystal clusters (CNCs), solvation liquid, photocurable resin. Superparamagnetic CNCs form to chain-like structure along the magnetic field line, and diffracted color result from the periodicity of chain-like structure. Diffracted color can be tuned through entire visible range simply by varying field intensity. Once desired diffracted color is obtained, corresponding chain-like ordered CNCs structures can be immobilized to the arbitrary morphology by solidifying the photocurable resin through instantaneous exposure of UV whose illumination pattern can be modulated with digital micromirror device (DMD). For the demonstration of photonic band gap mixing, we produced a photonic crystal layer at the bottom using the scheme described above, then we apply different magnetic field to the uncured M-Ink on top of the pre-produced photonic structure. After applying additional magnetic field, we shoot the UV light which passes through the first layer and create second layer of structural color. This sequential magnetic field application for photonic bandgap tuning and UV exposure for photonic crystal fixing technique can significantly reduce the efforts for precisely controlled multiple different photonic bandgap structure layers. Our strategy to create mixed structural color does not need to form structural color very small down to beyond human eye’s resolution. Also, structural color with large area would be easily achievable. The technique has the target applications including optical filters, forgery protection and new design materials.
3:45 PM - LL2.4
Dynamic Shape Control of Anisotropic Particles
Jaewon Yoon 1 , Sahar Rahmani 3 , Laura Chang 2 , Nicholas Clay 2 , Joerg Lahann 2 1 3 Show Abstract
1 Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States, 3 Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States
Numerous techniques have been used to synthesize anisotropic particles, as they have potential advantages in many applications such as multicomponent carriers for drug delivery, molecular imaging, optical device, and potential building blocks for three dimensional self-assembled structures. Attempts have been made to design new particles with breaking the symmetry and introducing anisotropic features such as shape, outer surface, and inner architecture. As one of the straightforward methods to fabricate anisotropic particles, we have previously demonstrated electrohydrodynamic (EHD) co-jetting to produce multicompartmental fibers and particles. Here, we report a new strategy to devise precisely-controlled anisotropic particles using a shape-shifting process through ultrasound treatment. When poly(lactide-co-glycolide) (PLGA) microcylinders were introduced with ultrasound in water, the particle temperature increased and they were converted into spheres due to surface energy effect. Expanding on our previous work, we have successfully combined EHD-co-jetting with this simple shape-shifting, and produced multicompartmental particles with well-defined structures. Moreover, we proceeded to incorporate PLGA with polymers with different properties including poly(methyl methacrylate) (PMMA) and poly(vinyl cinnamate) (PVCi). Shape-shifting of such polymeric particles resulted in various particle shapes, which, in turn, can affect future applications such as particle degradation, functionality, flow properties, and targeted efficiency of biomolecules.
4:30 PM - LL2.5
Two-photon Degradable Nanoparticles for Spatio-temporal Controlled Release in Biomedical Applications.
Adah Almutairi 1 , Jagadis Sankaranarayanan 1 Show Abstract
1 , University of California San Deigo, La Jolla, California, United States
Nanoparticles formulated from photodegradable polymers are useful biomaterials for spatiotemporal controlled release applications. Nanoparticles can be used to encapsulate bioactives for therapeutic and diagnostic applications while photodegradation offers spatial and temporal control over the release of the encapsulated materials (Fomina et al 2010). Moreover two-photon degradation allows for the use of Near IR (NIR) wavelengths of irradiation, which are non-ionizing compared with visible one photon irradiation. Additionally, NIR irradiation afforded by the two photon phenomena is within the tissue transparency window. Here we report the development of a novel two photon degradable monomer that has a high two photon uncaging action cross section. We incorporated the photodegradable moiety at 1mol%, 5mol% and 10mol% into a polyester backbone. We formulated particles from these polymers and encapsulated model proteins in them. We observed that we can control the nanoparticle degradation and thereby protein release based on the degree of incorporation of the photodegradable moiety using both one photon and two photon irradiation.
4:45 PM - LL2.6
Synthetic Nanoparticle-chaperoned Urinary ``biomarkers” for Noninvasive Cancer Diagnostics.
Gabriel Kwong 1 , Geoffrey von Maltzahn 1 , Omar Abudayyeh 1 , Steven Mo 1 , Sangeeta Bhatia 1 Show Abstract
1 Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Dysregulated protease activity underlie many stages in tumor progression, including angiogenesis, tissue invasion, and metastasis. Molecular diagnostic platforms to detect protease activity noninvasively will have broad utility in cancer detection and monitoring. We describe the development of long circulating nanoparticle probes that can survey, sense and report on protease activity by delivering peptide-based substrate libraries to tumors. Within the tumor microenvironment, active proteases cleave cognate peptides from the nanoparticle core, thereby triggering the accumulation of cleavage fragments into urine through renal filtration. These synthetic urinary “biomarkers” are predesigned with dual readouts—molecular dyes for bulk fluorescent detection and mass-encoded for multiplexed quantification by liquid chromatography tandem mass spectrometry (LC MS/MS). In an in vitro screen involving ~50 substrates, we identified 10 peptides with high activity for the matrix metalloprotease family of proteases that are frequently upregulated in tumors. These peptides were coated onto iron oxide nanoparticles, and following administration of these hybrid materials in tumor-bearing (MDA-MB-435/HT-1080) nude mice, we observed a ~2-3 fold increase in urine fluorescence over control animals. To deconvolute individual probes by mass spectrometry, we encoded the 10-plex protease substrate library with stable-isotope variants of the MS standard peptide Glu-fibrinopeptide B (Glufib) such that each individual mass code can be differentiated and quantified by LC MS/MS. In serial monitoring experiments involving multiple injections of the 10-plex peptide-nanoparticle library into pretumor and tumor bearing animals, we were able to detect and quantitate 10-plex mass signatures from urine by LC MS/MS. In nearest neighbor leave-one-out-cross-validation (LOOCV) analysis of the mass signatures, 33/36 urine samples were properly classified as tumor or pretumor samples. This strategy of administering prodiagnostic reagents and analyzing remote reporters is amenable to a broad range of protease-dependent complex diseases such as coagulopathies and liver fibrosis.
5:00 PM - LL2.7
In-situ Fabricated Polymeric Microrobot Using Programmable Heterogeneous Magnetic Nanoparticle Self-assembly.
Jiyun Kim 1 , Su Eun Chung 1 , Sung-Eun Choi 1 , Sunghoon Kwon 1 Show Abstract
1 Electrical engineering, Seoul National University, Seoul Korea (the Republic of)
The controlled locomotion of polymeric microrobots in a liquid environment is of interest both fundamentally and for biological applications. Several previous works have shown that the use of external magnetic fields is effective for moving millimeter and micrometer scale microcomponent using composite material comprised of magnetic nanoparticles and polymeric matrix. However, the difficulty in controlling and fixing the magnetic nanoparticle dispersion limits the elaborate motion control of microstructure because magnetic nanoparticle distribution determines magnetic anisotropy of polymer matrix. Therefore, new polymeric material system and fabrication method is required to build polymeric magnetic microstructure for complex 3-dimensional actuation. Here, we introduce 3-dimensionally creeping polymeric microrobot using new magnetic nanocomposite material system and in-situ fabrication method. The key idea is the combination of the self-assembly behavior of magnetic nanoparticles with spatially modulated maskless lithography. Magnetic nanoparticles tend to align along the magnetic field line and this alignment can be fixed in polymeric microstructure using maskless photolithography determining the magnetic anisotropy of the polymeric microstructure in a shape independent manner. We fabricate microrobot by repetitively tuning the nanoparticle assembly and fixing the assembled state via photopolymerization to program heterogeneous magnetic anisotropy. To guarantee the uniform assembly of magnetic nanoparticle and increase magnetic property controllability, we use chemically modified superparamagnetic nanoparticle. One crucial advantage of our system is that magnetic properties of polymeric microstructure, such as magnetic anisotropy or the amount of magnetization, are programmable. As mentioned above, the fixed alignment of magnetic nanoparticles in multiple polymerized regions creates heterogeneous magnetic anisotropy in the actuator. This enables a homogeneous magnetic field to independently actuate each component with the relative initial direction of chains determining the final configuration of the actuator. The microrobot is composed of four bodies which have different assembled states of magnetic nanoparticles. It shows various configurations according to the direction of the applied magnetic field line because each body bends towards the magnetic field line direction. By choosing the appropriate configurations, we show the creeping movement of 3-dimensional microlooper in a liquid environment. Our approach greatly simplifies the manufacturing process and also offers effective rules to design the improved magnetic microrobots for diverse microsystem applications.
5:15 PM - LL2.8
Supramolecular Nanostructures Designed for High Cargo Loading Capacity and Kinetic Stability.
Yi-Yan Yang 1 , Chuan Yang 1 , Jeremy P. K. Tan 1 , Amalina Attia 1 , Wei Cheng 1 , Shaun Lim 1 , Alshakim Nelson 2 , James Hedrick 2 Show Abstract
1 , Institute of Bioengineering and Nanotechnology, Singapore Singapore, 2 , IBM Almaden Research Center, San Jose, California, United States
The major obstacles for micellar drug-delivery systems are the lack of kinetic stability (when exposed to infinite dilution after their in vivo administration) and low cargo capacity of amphiphilic or hydrophilic drugs. Approaches such as covalently crosslinking the core or shell of premixed micelles, utilizing noncovalent interactions including hydrophobic and ionic interactions as well as stereocomplexation have been proposed to improve stability. Strategies designed to enhance the cargo loading levels have been less pervasive. Typically these strategies involve increasing the size of the hydrophobic block (although this strategy can adversely increase the size of the overall micelle-cargo complex), or enhancing carrier-cargo complexes using noncovalent interactions through molecular recognition to improve loading levels. Herein, we describe novel mixed micelles formed from urea- and acid-functional polycarboantes through acid-urea interactions to (1) address kinetic stability of micelles in ultra-dilute conditions, and (2) enhance loading levels of micelles for amphiphilic drugs.Urea- and acid-functional polycarbonates were synthesized by organocatalytic ring-opening polymerization of urea- and acid-functional carbonates using methoxy poly(ethylene glycol) (PEG) as a macroinitiator. These functional amphiphilic polycarbonates had a well-defined structure and narrow molecular weight distribution. Doxorubicin (DOX) was used as a model amphiphilic anticancer drug. The acid-functional polycarbonate sequestered DOX into micelles with high loading levels due to the acid-amine ionic interaction. However, the size of the micelles was large and the DOX-loaded micelles were not stable. In sharp contrast, the mixed micelles formed from the acid- and urea-functional polycarbonates provided not only high DOX loading capacity but also nanosize with narrow size distribution and kinetic stability. Importantly, DOX release from the mixed micelles was sustained over 6 hours without significant initial burst, and DOX-loaded mixed micelles killed HepG2 human liver carcinoma cells as efficiently as free DOX. In addition, these mixed micelles were non-cytotoxic. These biodegradable and non-cytotoxic mixed micelles can find important applications in delivery of anticancer drugs with amine functional groups.
5:30 PM - LL2.9
Biomimetic Controlled Release Microparticles for Enhancing Local Numbers of Regulatory T Cells.
Siddharth Jhunijhunwala 1 , G. Raimondi 1 , E. Nichols 1 , S. Thorne 1 , A. Thomson 1 , Steven Little 1 Show Abstract
1 Chemical Engineering, Bioengineering, and Immunology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
Regulatory T cells (Treg) are essential for controlling immune responses in the body. Given their important role in regulating immunity, it is well documented that increasing numbers of regulatory T cells (Treg) at local sites is a potential treatment option for autoimmune diseases and transplant rejection. At present, the only method of achieving increased local numbers of Treg is through systemic infusion ex vivo cultured cells (a method plagued with problems). As an alternative strategy, we have developed 2 distinct (but inter-related) biomimetic formulations that can be used to dramatically increase local populations of Treg in vivo.The first biomimetic formulation that we prepared was a microparticle based system for the release of CCL22 (a chemokine used by tumors to recruit Treg in the body). We demonstrate sustained, long term release of CCL22 from microparticles, which allowed for recruitment and co-localization of Treg with the particles in an in vivo model for cellular migration. Additionally, we observe that CCL22 microparticles are able to significantly prolong the survival of allogeneic transplants. As another distinct strategy to increase local numbers of Treg, we have identified a specific set of factors to expand these cells as well as to induce conversion of naïve T cells to Treg. Encapsulation and controlled release of these factors into microparticles (achieved by us and others) allows us to mimic tolerogenic cells that expand Treg in vivo through the secretion of some of the same factors. We are in the process of testing the efficacy of the factor-encapsulating formulations in aiding the induction and expansion of Treg in vivo.In conclusion, we have successfully developed biomimetic formulations for the recruitment and expansion of Treg at local sites in vivo. Each of these formulations either individually or in combination may have the potential to be developed into a therapeutic for autoimmunity and transplant rejection.
Joerg Lahann University of Michigan
StevenR. Little University of Pittsburgh
Samir Mitragotri University of California-Santa Barbara
Matthew Tirrell University of California, Berkeley
LL4: Designer Particles: Theory Meets Practice
Thursday AM, April 28, 2011
Salons 10-11 (Marriott)
9:30 AM - **LL4.1
Flow Lithographic Methods to Create Biomimetic Materials.
Patrick Doyle 1 Show Abstract
1 Chemical Engineering, MIT, Cambridge, Massachusetts, United States
The synergy of controlled microfluidic flows and lithographic patterning of materials offers an attractive route to synthesize new colloidal materials. In this talk we will discuss the development of a new class of “soft” colloidal suspensions that are inspired by cellular motifs. We build off the Stop Flow Lithography technique to synthesize non-spherical, soft hydrogel particles with dimensions comparable to cells. In particular, we present results of particles which mimic some properties of red blood cells. Of particular interest is to understand how we can engineering shapes which present distinct passage properties, evolution in time, and regio-specific compartments.
10:00 AM - LL4.2
Biodegradable Nanostructures with Selective Lysis of Microbial Membranes.
James Hedrick 1 , Ying Zhang 2 , Nederberg Fredrik 1 , Jeremy Tan 2 , Kazuki Fukushima 1 , Daniel Coady 1 , Yi-Yan Yang 2 Show Abstract
1 , IBM Research, San Jose, California, United States, 2 , Institute of Bioengineering and Nanotechnology, Singapore Singapore
Due to the increasing resistance of bacteria to conventional antibiotics (e.g. ciprofloxacin, doxycycline and ceftazidime), new strategies must continuously be employed. Most conventional antibiotics do not physically damage the cell wall but act on specific protein targets within the microorganism. As a consequence, the bacterial morphology is preserved and the bacteria can easily develop resistance if it is not killed outright. In contrast, most cationic antimicrobial peptides do not have a specific protein target, but instead interact with the microbial membrane based on electrostatic interactions and thus damage the membrane directly. A number of cationic polymers that mimic the facially amphiphilic structure and antimicrobial functionalities of these peptides have been proposed. However, since most of the proposed polymers are non-biodegradable they have met limited success for in vivo applications. We will describe a biodegradable antimicrobial amphiphilic polymer based on a new design principle, i.e. self-assembly of block copolymers containing cationic (or hydrophilic) and hydrophobic polycarbonate blocks into cationic micelles. The formation of nanostructures in solution before in contact with cell surfaces is believed to increase the local concentration of cationic charge and polymer mass, leading to enhanced interactions with negatively-charged cell walls, and thus stronger antimicrobial activities. We also describe other monomers designed to balance the hydrophobic-hydrophilic interactions, analogous to natural peptides, to tackle both gram negative and gram-positive bacteria. Since our approach is based on cationic nanostructures, we propose to enhance the activity of this platform by transforming the spherical nanoparticles into elongated, high aspect ratio nanoparticles to develop a universal strategy towards both types of bacteria.
10:30 AM - LL4.4
Functional Nanoscale Polymers for Controlling/Studying Material-cell Interactions.
Ishrat Khan 1 , Jereme Doss 1 , Biswajit Sannigrahi 1 , Barbara Baird 2 , Deepti Gadi 2 Show Abstract
1 , Clark Atlanta University, Atlanta, Georgia, United States, 2 Department of Chemistry, Cornell University, Ithaca, New York, United States
Functionalized nanomaterials have an expansive range of potential uses in biomedical applications. Functionalized synthetic (biocompatible and/or biodegradable) polymers that control or monitor cell signaling can be effective antagonists and promising drug candidates. We have developed two functional polymer systems (with dimensions in the nanoscale) which are effective inhibitors of degranulation of mast cells stimulated by a potent allergen. The inhibition is possible because of the specific interaction of the functional polymers with the proteins (IgE) on the mast cell surfaces to control cell-signaling i.e. intelligent design of functional materials to manipulate cellular functions. One of the system is the nanoscale macromolecules based on water soluble, bifunctional sulfonated bis-DNP(2,4-dinitrophenyl)-poly(2-methoxystyrene) based ligands. The second functional polymer system is the di-functional, tri-functional and tetra-functional (DNP) polymers based on the biodegradable poly(lactides). Both polymeric systems are effective inhibitors of degranulation of mast cells stimulated by a potent allergen. The preparation, characterization, processing and effectiveness of the functional polymers to control material-cell interactions will be discussed.
10:45 AM - LL4.5
Polymer Microparticles Anisotropically Functionalized with Rippled Gold Nanoparticles for Targeting of Human Endothelial Cell Membranes.
Tae-Hong Park 1 , Asish Misra 2 , Dong Woo Lim 1 , Thomas Eyster 1 , Sangyeul Hwang 1 , Randy Carney 3 , Francesco Stellacci 3 , Joerg Lahann 1 2 4 Show Abstract
1 Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 Biomedical Engineering, Univeristy of Michigan, Ann Arbor, Michigan, United States, 3 Supramolecular NanoMaterials and Interfaces Laboratory, EPFL, Lausanne Switzerland, 4 Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States
Hierarchical architectures of polymer particles with nano- and microscale anisotropy have been recently emerging. Building blocks at different length scales can simultaneously present different physical and chemical properties to hybrid materials and the controlled introduction of functional nanomaterials may give rise to directionally multifunctional platforms for smart materials in industrial and biomedical applications. Here we demonstrate that polymer microparticles, which are anisotropically modified with cell-penetrating gold nanoparticles (AuNP), were able to strongly interact with cells via direct penetration of hierarchically structured Janus particles into the cell membrane. We prepared biphasic polymer microparticles via electrohydrodynamic co-jetting of polymer solutions with a side-by-side geometry; one side contained an amine functionalized polymer and the other consisted of an acetylene functionalized polymer. The reaction with N-hydroxysuccimide ester-terminated polyethylene glycol (NHS-PEG) selectively modified the amine containing compartment, resulting in anisotropic brushes of the biphasic polymer particles. The copper(I)-catalyzed Huisgen 1,3-dipolar cycloaddition of N3-poled rippled gold nanoparticles (AuNPs) preferentially functionalized the other compartment containing acetylenes. Because rippled surface pattern of divalent gold nanoparticles allow for direct cell-penetration and PEG brushes prevent protein adsorption under physiological conditions, unidirectional interaction between AuNP conjugated polymer particles and human endothelial cells can be observed. This result underlines that precisely engineered anisotropic inorganic/organic hybrid can contribute to further developments in emerging areas such as smart materials or particle-based therapeutics.
11:30 AM - **LL4.6
Design of Nano- and Micro-Particles for Self-assembly and Reconfigurability.
Sharon Glotzer 1 Show Abstract
1 Departments of Chemical Engineering and Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States
Nanoparticles comprise a new generation of materials building blocks because of their diversity of shape, material and size, and because they can be patterned and functionalized down to molecular scales with tailored and programmable interactions. The ability to create designer particles opens up exciting opportunities to create building blocks designed for self-assembly and even reconfigurability, in part through biomimicry. We show how, in the absence of a predictive theory, computer simulations play a critical role in elucidating how particle shape, interactions, and programmability can be exploited and designed to achieve a high propensity for self-assembly into complex structures, including sheets, wires, helices, open structures, complex crystals and quasicrystals.
12:00 PM - LL4.7
In Vitro Transmission Electron Microscopy of Functional Nanoparticles.
Kate Klein 1 , Niels de Jonge 2 , Ian Anderson 1 Show Abstract
1 Surface and Microanalysis Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland, United States, 2 Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, United States
With the growing applications of nanoparticles, especially in health-related fields, there is rising concern over the yet undetermined toxicity and fate of engineered nanoparticles upon their release into our bodies and our surroundings. Toxicology studies in the literature consist of highly conflicting, difficult-to-compare results, due in part to uncertainties and lack of uniformity in critical properties such as hydrodynamic size distribution, aggregation behavior, and reactivity in solution. There is an urgent need for a characterization technique that combines the ability to image and analyze functional nanostructures in their relevant aqueous (“in vitro”) environment with the high spatial resolution necessary to probe individual nanostructures. The additional capacity to flow liquid through the probed region would also enable dynamic studies, thus providing a unique method to monitor the behavior of functionalized nanoparticles in an in vitro environment.This research addresses the above challenge by establishing methods for the characterization of nanoparticles in solution using a customized transmission electron microscopy (TEM) liquid flow cell specimen holder. Data were acquired using a microfluidic cell, comprised of two silicon microchips with electron transparent silicon nitride windows, that interface with a prototype holder providing fluid circulation through the cell from the outside of the electron microscope. We report on the imaging and energy-loss characteristics of the microfluidic flow cell system using 300 kV conventional TEM, specifically relating the effect of multiple inelastic scattering in the fluid layer to spatial resolution arising from limitations due to chromatic aberration. Furthermore, we demonstrate the utility of this technique for in vitro imaging of functional nanoparticles through preliminary studies of citrate-stabilized metal nanoparticles. The ability to observe directly nanoparticle attributes and behavior in relevant media will provide crucial information for related in vivo studies.
12:15 PM - LL4.8
Elastin-like Polypeptide Vesicles for Drug Delivery.
Kristen Carpenter 1 , Logan May 1 , Kimberly Woodhouse 2 , Robin Hissam 1 Show Abstract
1 Chemical Engineering, West Virginia University, Morgantown, West Virginia, United States, 2 Chemical Engineering, Queen's University, Kingston , Ontario, Canada
Elastin-like polypeptides have been investigated for drug delivery applications because of the ability to aggregate these molecules in hyperthermal environments. These molecules are often directly coupled to drug molecules for the targeted delivery of the drug to a specific tissue, such as a tumor, where an elevated temperature drives the agglomeration of the polypeptide. A different approach to creating drug delivery vehicles has been focused on, using the self-assembly behavior of elastin-like polypeptides. Amino acid sequences derived from the primary structure of tropoelastin contain both hydrophobic domains of [VPGVGA] and crosslinking domains rich in alanine and lysine. These molecules undergo an LCST with similar to other elastin-like polypeptide sequences and have multiple reactive groups that can be used to functionalize or crosslink the polypeptides. The transition temperature for this molecule, although near room temperature, can be manipulated through modifications to the peptide sequence, creating a material that will change phase near or above body temperature. In addition to controlling the transition temperature, the assembled structure has been manipulated through modifications to polypeptide backbone. At the onset of assembly, the elastin-like polypeptide forms solid spheres with a bimodal distribution of sizes, in the nanometer and micron ranges. These solid spheres offer potential for drug molecules to be entrapped within the polypeptide aggregate, however, this project has focused on the manipulation of the elastin-like polypeptide chemistry to create vesicle or reverse micelle structures. Taking a cue from block copolypeptide molecular behavior, the coupling of a hydrophilic polymer to the reactive groups within the polypeptide, forming block or graft hybrid polymers, has been investigated to create the hollow spherical structures. The hybrid block structure was formed by attaching polyethylene glycol to the terminal carboxyl group of the elastin-like polypeptide, while the polymer was attached to amine groups on the lysine residues to create a graft structure. The incorporation of polyethylene glycol increases the inverse transition temperature of the polypeptide, but also results in hollow spherical structures. These particles have been characterized by scanning electron microscopy and confocal microscopy. These particles have also been manipulated by changing the density and molecular weight of the polyethylene glycol. Because these molecules are based on natural sequences, the spherical structures are promising as biocompatible drug delivery vehicles.
12:30 PM - LL4.9
Biomimetic ``Soft"-``Hard" Core-shell Microcapsules.
Mark Bewernitz 1 , Laurie Gower 1 Show Abstract
1 Materials Science & Engineering, University of Florida, Gainesville, Florida, United States
Calcareous dinoflagellate cysts, sometimes referred to as “calcispheres”, are from biomineralizing organisms that form a protective calcium carbonate shell around the single celled organism during the vegetative state. The templating capability for forming a patterned array of calcite crystals on the surface of the organisms has served as our inspiration for depositing a mineral shell around fluidic particles, such as emulsion colloids. In our biomimetic design, we have prepared soft-hard microcapsules containing a fluidic core, such as an oil droplet (n-tetradecane), coated with a mineral shell of CaCO3. These microcapsules are produced by coating charged surfactant-stabilized emulsion colloids with a mineral shell using a polymer-induced liquid-precursor (PILP) mineralization process, which generates liquid-liquid phase separation of nanodroplets of a mineral precursor that adsorb to the emulsion template, and coalesce to form a smooth and continuous mineral shell that encapsulates the oil droplets. Active agents and other ingredients that are present in the emulsion can thus be encapsulated for controlled release applications. Our more recent studies have focused on the capsule formation on liposome templates, which then provide the ability to encapsulate water and oil soluble agents. These biodegradable microcapsules are envisioned for use in a variety of commercial applications, ranging from pharmaceutical microcapsules for drug delivery, agriculture (release of catalyst, pesticide, fertilizer), consumer products (cosmetics, skin and hair care), and self-healing composites.
12:45 PM - LL4.10
Screening and Designing Patchy Particles for Self-assembly Propensity through Assembly Pathway Engineering.
Eric Jankowski 1 , Sharon Glotzer 1 2 Show Abstract
1 Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States
Patchy particles are an attractive modeling paradigm for biologically relevant engineering applications because of their promise for self-assembling specific patterns and structures with characteristic lengths tunable for biosensing and drug delivery applications, and because patchy particles also enable modeling of proteins on timescales orders of magnitude longer than the fluctuation timescale of a protein's internal degrees of freedom. One frontier in self-assembly theory is understanding the roles patchy particle shape and interaction anisotropy play in their ability to self-assemble ordered patterns. In this work we provide a framework for designing patchy particles for robust self-assembly of target patterns that utilizes a new pathway focused assembly engineering strategy. By efficiently generating the assembly pathways for patchy particles we can identify kinetic traps to assembly with shape matching algorithms and quantify the degree to which the traps prevent robust assembly. Patterns of traps in the pathways inform strategies for avoiding these traps, and we use the pathways to identify experimental conditions where self-assembly is optimized. We demonstrate the utility of our approach for several systems, including biomimetic assemblies of CdTe tetrahedra.
LL5: Custom-tailored Nano- and Microparticles
Thursday PM, April 28, 2011
Salons 10-11 (Marriott)
2:30 PM - **LL5.1
Lateral Segregation in Block Copolymer Assemblies: From Ligand-induced Janus Vesicles to Half-crystalline Worm Micelles.
Dennis Discher 1 Show Abstract
1 , Univ Pennsylvania, Philadelphia, Pennsylvania, United States
In cell biology, adhesions are made effective by strengthening via receptor clustering or 'rafts', but the development of pre-clustered targeting domains on particles useful for delivery requires a means to create ‘patchy particles’. Selective binding of multivalent ligands within a mixture of polyvalent amphiphiles provides, in principle, a first simple mechanism for making patchy particles. Divalent cations will be shown to crossbridge polyanionic amphiphiles, which thereby demix from neutral amphiphiles and form spots or rafts within bilayer vesicles as well as stripes within wormlike micelles . Coarse-grained MD simulations are ongoing and aim to clarify mechanisms of interleaflet coupling within the bilayer. In a second set of studies, we examine semicrystalline block copolymers and discover lateral segregation in wormlike micelles. A crystallizable chain within a diblock copolymer assembly is expected to couple curvature to crystallization and thereby impact rigidity as well as preferred morphology, but the effects on dispersed phases have remained unclear. The hydrophobic polymer polycaprolactone (PCL) is semi-crystalline in bulk (Tm = 60 C) and will be shown to generate flexible worm micelles, half-rigid worms, or rigid vesicles in water from several dozen polyethyleneoxide-based diblocks (PEO-PCL). Only a few worms appear rigid at room temperature (T << Tm), indicating suppression of crystallization by both curvature and PCL hydration. Worm rigidification, which depends on molecular weight, is also prevented by copolymerization of caprolactone with just 10% racemic lactide that otherwise has little impact on bulk crystallinity. In contrast to worms, vesicles of PEO-PCL are always rigid and typically leaky. Defects between crystallite domains induce dislocation-roughening with focal leakiness. Hydration in dispersion thus tends to selectively soften high curvature microphases. Altogether, the results highlight an emerging ability to spatially control lateral patterning in self-assemblies.REFERENCES: (1). DA Christian et al. Nature Materials 8: 843–849, 2009. (2) K Rajagopal et al. Macromolecules (to appear)
3:00 PM - **LL5.2
Tumor-penetrating Peptides in Targeted Delivery of Nanoparticles.
Erkki Ruoslahti 1 Show Abstract
1 Vascular Mapping Center, Center for Nanomedicine, Sanford Burnham Medical Research Institute, Santa Barbara, California, United States
This laboratory screens phage libraries in live mice to identify peptides that direct phage homing to a specific target in the body. As the phage is a nanoparticle, it is primarily confined to the vessels, and the screening primarily targets tissue-specific or tumor-specific differences in endothelial cells. The homing peptides from these screens have revealed a zip code system of molecular changes in blood vessels of normal tissues, and in tumor blood vessels and lymphatics. The power of in vivo phage screening is illustrated by the discovery of tumor-penetrating iRGD peptide (CRGDKGPDC). This peptide contains the integrin-binding RGD sequence, which mediates tumor homing through binding to integrins that are selectively expressed in tumor vasculature and on tumor cells, but the tumor penetrating properties of this peptide are unique. The iRGD peptide contains a second active sequence motif, R/KXXR/K, which we named the C-end Rule or CendR. The term refers to the fact that this sequence is only active when the second arginine residue is exposed at the C-terminus of the peptide. Proteolytic processing of iRGD in tumors activates the CendR motif. The CendR sequence binds to neuropilin-1, which in turn activates at transport pathway through tumor tissue. The CendR technology provides a solution to a major problem in tumor therapy, poor penetration of drugs into tumors. The tumor-penetrating peptides can take a payload deep into tumor tissue in mice. They also penetrate into human tumors ex vivo. Targeting with these peptides increases the accumulation in tumors of a variety of drugs, such as doxorubicin, antibodies and nanoparticles. The increase can be up to 40 fold. Remarkably the drug or nanoparticle to be targeted does not have to be coupled to the peptide; the peptide activates a bulk transport system that sweeps along any compound that is present in the blood.
3:30 PM - LL5.3
Tuning of Microbubble Response to Ultrasound through DNA Crosslinking of the Encapsulating Shell.
Matthew Nakatsuka 1 , Mark Hsu 2 , Sadik Esener 2 3 , Jennifer Cha 3 , Andrew Goodwin 3 Show Abstract
1 Materials Science and Engineering, University of California, San Diego, La Jolla, California, United States, 2 Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, United States, 3 Nanoengineering, University of California, San Diego, La Jolla, California, United States
Ultrasound is the second-most widely used imaging technology in the world because it is safe, non-invasive, and effective. To improve the quality of ultrasound imaging, contrast agents such as gas-filled microbubbles have been adopted to allow for the detection and diagnosis of many diseases. If insonated at specific resonance frequencies with sufficient power, microbubbles oscillate at specific characteristic frequencies, generating signals that are easily distinguished. However, there currently exists no contrast agent that can be activated in a specific biochemical environment to sense for diseases or inflammation in vivo. Here, we report a novel microbubble formulation that incorporates DNA-poly(acrylic acid)-lipid conjuates into the encapsulating shell. Hybridization of the DNA side groups created crosslinks within the shell, which prevented microbubble oscillation and muted the resulting signal. Thus, the magnitude of the ultrasound signal during imaging can be used to determine the presence of analyte biomolecules. By selecting cleavable sequences as crosslinkers, the presence of enzymes associated with certain diseases, such as excess amounts of thrombin indicating deep venous thrombosis, can be identified far earlier than by current methods.
3:45 PM - LL5.4
Water Soluble Wormlike Polymer Brushes: Synthesis and Characterization.
Peng Zhao 1 , Xiaoqin Feng 2 , Lixin Liu 2 , Yongming Chen 1 Show Abstract
1 Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, The Chinese Academy of Sciences, Beijing China, 2 College of Life Science, Graduate University of the Chinese Academy of Sciences, Beijing China
Wormlike polymer brush is defined as a linear macromolecule with polymeric side chains being highly densely grafted along a polymer main chain. Attributing to the hindrance repulsion between the adjacent bulky branches, the backbone is forced to extend from a random coil to a semi-flexible cylinder, exhibiting wormlike morphology as a unimolecular nanoobject. The length of molecular worms can easily reach hundreds of nanometers depending upon the degree of polymerization (DP) of backbones. Moreover, when the backbones are obtained by controlled polymerization, the length of polymer brushes can be tailored. Therefore, polymer brush is very important if wormlike morphology and the shape-resulted properties are considered. In the past ten years, synthetic methodology and physical properties of the polymer brushes have been studied. They have also been studied as a template to fabricate inorganic nanoparticles of one dimension. However, there are few reports to evaluate the properties of water soluble polymer brushes for exploring their application in nanomedicine. Herein, we report the synthesis of water soluble polymer brushes by click chemistry and also we are exploring the application of these well-define molecular worms in drug delivery. The polymer brushes were synthesized by graft-onto approach. Firstly poly(glycidyl methacrylate) (PG) was prepared by atom transfer radical polymerization and the well defined PGs with the degree of polymerization up to 1000 have been obtained. Then the epoxy groups were transferred into azides quantitatively by reaction of PG and sodium azide and the azide functionalized backbone-to-be polymers (PGA) were obtained. Secondly the alkyne terminated poly(ethylene glycol) (APEG) and poly(epsilon-caprolactone)-b-poly(ethylene glycol) (APCL-b-PEG) were obtained respectively. Then PGAs were reacted with APEG and APCL-b-PEG by Cu(I)-catalyzed click reaction respectively to give PEGylated polymer brushes, P(G-g-PEG), and amphiphilic core/shell polymer brushes, P(G-g-(PCL-b-PEG)). The grafting ratio along the backbone was above 60 % and even to 90 %, demonstrating that this is an efficient synthetic methodology. For the brushes with the degree of polymerization to be ca. 1000, the molecular brushes in wormlike morphology were visualized by atom force microscopy and the contour length reached 200-300 nm. Furthermore, the polymer brushes were labeled with Rhodamine B in situ by covalent bonding during the brush formation. Using these molecular worms, we have explored the cell internalization and delivery Doxorubicin preliminarily.
4:30 PM - **LL5.5
Novel Methods of Enhanced Retention in and Rapid, Targeted Release from Liposomes.
Joseph Zasadzinski 1 Show Abstract
1 Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota, United States
Liposomes are single bilayer capsules with distinct interior compartments in which hydrophilic drugs, imaging agents, diagnostics, etc. can be sequestered from the exterior environment. The polar parts of the individual lipids face the water compartments, while the hydrophobic parts of the lipid provide a barrier in which hydrophilic or charged molecules are poorly soluble. The bilayers are typically from 3 - 6 nm thick and the liposome can range from about 50 nm - 50 microns in diameter. The question to be addressed is if any one bilayer, regardless of its composition, can provide the extended drug retention, long lifetime in the circulation, active targeting to specific tissues and rapid and controllable drug release at the site of interest necessary for an optimal drug carrier. As an alternative, new methods of self-assembling multicompartment lipid structures provide enhanced drug retention in physiological environments. We also review methods of externally targeting and triggering drug release via the near infrared heating of gold nanoshells attached to or encapsulated within bilayer vesicles.
5:00 PM - LL5.6
Constructing Templates for One-dimensional Nanostructure Uusing DNA Origami.
Ian Robertson 1 , Testuo Kodera 1 , Yasuko Yanagida 2 , Ken Uchida 1 , Shunri Oda 1 Show Abstract
1 Physical Electronics and Quantum Nanoelectronics, Tokyo Institute of Technology, Tokyo Japan, 2 Precision and Intelligence Lab., Tokyo Institute of Technology, Yokohama Japan
A 72 x 26nm DNA origami with a 22 x 28nm square punch-hole was designed and constructed to be used as template to grow silicon nanowires from. The inner square punch-hole was used to place 5nm colloidal Au seeds along the rim. This is so that the seeds may be planted on selected etched regions of silicon created by EBL. Templates were removed via O2 plasma so that a pattern layer of colloidal Au is left behind. Using a low pressure chemical vapor deposition (LPCVD), the sample reacted towards the precursor Si2H6 to grow our silicon nanowires from the pattern layer of colloidal Au.Origami structure was designed using a cad program called caDNAno created by Douglas group . Staple strand were synthesis and purchased from Star Oligo Rikaken. M13mp18 bacterial viruses were obtained from New England Biolabs branched in Japan, 5nm Colloidal Au from British Biocell International while the remaining chemicals were purchased from Sigma-Aldrich. Using previous methodology we constructed our origami structure using a TaKaRa PCR, where upon after, we placed 5nm colloidal au along the inner rim   . DNA Origami templates results were observed under a SII Scanning Probe Microscope Multi-Function unit using DFM mode and silicon scanning tip. Nanowires were observed under Scanning Electron Microscope. In the current trend of lithography technology, the cost of production is becoming staggeringly expensive as transistor reach down towards 22nm or less. Fearing that the cost of raw materials and power usage maybe overwhelming, many industries and institute has look towards molecular self-assembly as an alternative to continue scaling down and creating novel devices. DNA origami however, has given us that alternative route. Nevertheless, techniques like DNA origami are still dependent on top-down methods to produce large scale patterns. Gold nano particles are known to be an excellent catalyst seed to grow silicon nanowires. Using such precursors like Si2H6 under vapor liquid solid (VLS) method, silicon nanowires can be grown in a chemical vapor deposition (CVD) machine . Although, pattern arrays of Silicon nanowires with controlled spatial deference, is difficult to achieve through traditional gold deposition techniques since the layer are not always uniform. Yet, for such application like solar cells, it is important that nanowires are grown homogeneously from pattern layer with extreme between resolutions. Fortunately, DNA origami, has given us that opportunity.1.H. Dietz, S. M. Douglas, W. M. Shih, Science 325 (2009) 725–30.2.P. W. K. Rothemund, Nature 440 (2006) 297.3.A. M. Hung, C. M. Micheel, L. D. Bozano, L. W. Osterbur, G. M. Wallraff, J. N. Cha, Nature Nanotechnology 5 (2010) 1–6.4.K. Sarveswaran, B. Gao, K. N. Kim, G. H. Bernstein, M. Lieberman (Eds.),volume 7637, SPIE, 2010.5.S. Akhtar, K. Usami, Y. Tsuchiya, H. Mizuta, S. Oda, Applies Physics Express 1 (2008) 014003–1.
5:15 PM - LL5.7
Stabilization of Nanoparticles under Biological Assembly Conditions using Peptoid Oligomers.
David Robinson 1 , George Buffleben 1 , Mary Langham 1 , Ronald Zuckermann 2 Show Abstract
1 , Sandia National Laboratories, Livermore, California, United States, 2 Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Inorganic nanoparticles usually rely on organic ligands to control growth, prevent aggregation, and to provide solubility and useful chemical functionality. The number of different ligands of proven value - especially that satisfy more than one of those criteria - is rather small. Ligands that are peptoids, or sequence-specific N-functional glycine oligomers, allow precise and flexible control over the arrangement of binding groups, steric spacers, charge, and other functionality. We have synthesized peptoids that prevent the aggregation of gold nanoparticles in molar concentrations of monovalent salt and high concentrations of divalent salt, above those needed for compatibility with biological diagnostic and therapeutic applications and with DNA origami-based nanostructure synthesis. Particles that are monofunctionalized with DNA have been prepared. The degrees of precision and versatility afforded by sequence-specific oligomer ligands are likely to prove essential in bottom-up assembly of nanostructures and in biomedical applications of nanomaterials.
5:30 PM - LL5.8
Self Assembly and Reconfigurability of Shape-changing Nano and Micro Particles.
Trung Nguyen 1 , Sharon Glotzer 1 2 Show Abstract
1 Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States
Engineering nanostructures through self-assembly is desirable for a wide variety of next-generation applications including drug delivery, autonomous sensing and reconfigurable materials. We present simulation studies of several candidate ordered structures assembled by nano- and micro-particles that are able to reversibly reconfigure in response to changes in building block shape. As one example, we report a reversible transformation between two ordered structures assembled by laterally tethered rods with different rod lengths. When the rod segments are lengthened or shortened in a short period of time as compared to the system relaxation time, a reversible transformation between those structures is induced. The kinetic effects due to rod shortening and expanding are shown to enhance the transformation process over the counterpart self-assembly process from disorder states. We also investigate the reconfigurability between ordered structures when the building blocks are deformed in a controllable manner. Our findings serve to motivate and guide the fabrication of shape-changing building blocks for assembling higher order nanostructures at nanometer and micron scales.ReferencesT. D. Nguyen, S. C. Glotzer, Reconfigurable assemblies of shape-changing nanorods, ACS Nano 4, 2585, 2010.
5:45 PM - LL5.9
Biodegradable PEG Star Polymers via Organocatalytic ROP: Nanoparticle Delivery Vehicles Tailored for Optimal Receptor-mediated Endocytotic Uptake by Animal Cells.
Joseph Sly 1 , Timothy Nguyen 2 , Eric Apple 1 , Victor Lee 1 , Melia Tjio 2 , James Hedrick 1 , Melanie McNeil 2 , Robert Miller 1 Show Abstract
1 Advanced Organic Materials, IBM Almaden Research Center, San Jose, California, United States, 2 Dept Chemical and Materials Engineering, San Jose State University, San Jose, California, United States
Poly(ethylene glycol) (PEG) decorated nanoparticles are extremely attractive materials targets for a range of biomedical applications. Key challenges still persist, however, in the design and creation of PEG-based nanoparticles for in vivo use, such as having a sufficiently dense PEG surface coverage to maintain solubility, promote directed nanoparticle uptake or avoid phenomenon such as accelerated blood clearance. The creation of such nanoparticles which are also capable of complex functions such solvating, transporting and releasing hydrophobic drugs in vivo is more difficult still. Advanced challenges include creating biodegradable “PEGylated” nanoparticle drug delivery vehicles with tailored polyvalent surface chemistries that are small enough to maximize the rate of receptor-mediated endocytotic uptake in animal cells (≈ 25 - 30 nm) but large enough to avoid renal system clearance prior to degradation. Star polymers (uni-molecular, globular, polymer architectures) are an increasingly attractive class of organic nanoparticles for biomedical research purposes. Topographically similar to dendrimers (i.e. a high local density of polymeric arms, surface functionality and interstitial regions) they lack the synthetic and structural limitations of dendrimers and the dynamic instability of micelles and liposomes. Nanogel star polymers, i.e. those with polymer “arms” connected to a cross-linked polymer core, in particular, offer great potential for variation in nanoparticle structure and surface functional (i.e. arm) density but are among the most synthetically demanding of polymeric nanostructures. To date, the few attempts at generating PEG-based nanogel star polymers have resulted in non-biodegradable nanoparticles, produced large and ill-defined structures, and/or use synthetic methodologies based on toxic metal catalysts such as copper and tin. Consequently there has been limited work done on PEG-based nanogel star polymers as a nanoparticle platform for drug delivery. Herein we report the first use of non-metal organocatalysis for ring opening polymerization (ROP) to form highly uniform, bio-degradable nanogel star polymers. We demonstrate this new technique by creating the first PEG-based nanogel star polymers with size and polyvalent surface chemistry tailored toward that recently predicted for optimal receptor-mediated endocytotic uptake in animal cells and the first nanoparticles in this class to both upload hydrophobic cargo and release it under physiological conditions.