School of Chemistry - Research Publications
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ItemOne-Step Assembly of Coordination Complexes for Versatile Film and Particle Engineering(AMER ASSOC ADVANCEMENT SCIENCE, 2013-07-12)The development of facile and versatile strategies for thin-film and particle engineering is of immense scientific interest. However, few methods can conformally coat substrates of different composition, size, shape, and structure. We report the one-step coating of various interfaces using coordination complexes of natural polyphenols and Fe(III) ions. Film formation is initiated by the adsorption of the polyphenol and directed by pH-dependent, multivalent coordination bonding. Aqueous deposition is performed on a range of planar as well as inorganic, organic, and biological particle templates, demonstrating an extremely rapid technique for producing structurally diverse, thin films and capsules that can disassemble. The ease, low cost, and scalability of the assembly process, combined with pH responsiveness and negligible cytotoxicity, makes these films potential candidates for biomedical and environmental applications.
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ItemPeptide-Tunable Drug Cytotoxicity via One-Step Assembled Polymer Nanoparticles(WILEY-V C H VERLAG GMBH, 2014-04)A novel class of nanoparticles is developed for the co-delivery of a short cell penetrating peptide and a chemotherapeutic drug to achieve enhanced cytotoxicity. Tunable cytotoxicity is achieved through non-toxic peptide-facilitated gating. The strategy relies on a one-step blending process from polymer building blocks to form monodisperse, PEGylated particles that are sensitive to cellular pH variations. By varying the amount of peptide loading, the chemotherapeutic effects can be enhanced by up to 30-fold.
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ItemEndocytic pH-Triggered Degradation of Nanoengineered Multilayer Capsules(WILEY-V C H VERLAG GMBH, 2014-03)The synthesis of cross-linker free layer-by-layer (LbL) capsules that solely utilize cellular pH variations as a trigger to specifically deconstruct and subsequently release cargo in cells is reported. These capsules demonstrate retention of water-soluble therapeutic molecules as small as 500 Da at extracellular pH. Triggered capsule degradation and release of cargo is observed within 30 min of cell uptake.
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ItemEndocytic Capsule Sensors for Probing Cellular Internalization(WILEY, 2014-10)A new class of polymer capsules with an in-built endocytic pH-coupled fluorescence switch is reported. These capsules display reversible "on/off" fluorescence in response to cellular pH variations. Using this system, the high-throughput quantification between surface-bound and internalized capsules is demonstrated. This system allows a fundamental study of the interaction between nanoengineered materials and biological systems at a cellular level.
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ItemTuning Particle Biodegradation through Polymer-Peptide Blend Composition(AMER CHEMICAL SOC, 2014-12)We report the preparation of polymer-peptide blend replica particles via the mesoporous silica (MS) templated assembly of poly(ethylene glycol)-block-poly(2-diisopropylaminoethyl methacrylate-co-2-(2-(2-(prop-2-ynyloxy)ethoxy)ethoxy)ethyl methacrylate) (PEG45-b-P(DPA55-co-PgTEGMA4)) and poly(l-histidine) (PHis). PEG45-b-P(DPA55-co-PgTEGMA4) was synthesized by atom transfer radical polymerization (ATRP), and was coinfiltrated with PHis into poly(methacrylic acid) (PMA)-coated MS particles assembled from different peptide-to-polymer ratios (1:1, 1:5, 1:10, or 1:15). Subsequent removal of the sacrificial templates and PMA resulted in monodisperse, colloidally stable, noncovalently cross-linked polymer-peptide blend replica particles that were stabilized by a combination of hydrophobic interactions between the PDPA and the PHis, hydrogen bonding between the PEG and PHis backbone, and π-π stacking of the imidazole rings of PHis side chains at physiological pH (pH ∼ 7.4). The synergistic charge-switchable properties of PDPA and PHis, and the enzymatic degradability of PHis, make these particles responsive to pH and enzymes. In vitro studies, in simulated endosomal conditions and inside cells, demonstrated that particle degradation kinetics could be engineered (from 2 to 8 h inside dendritic cells) based on simple adjustment of the peptide-to-polymer ratio used.
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ItemEngineering Poly(ethylene glycol) Particles for Improved Biodistribution(AMER CHEMICAL SOC, 2015-02)We report the engineering of poly(ethylene glycol) (PEG) hydrogel particles using a mesoporous silica (MS) templating method via tuning the PEG molecular weight, particle size, and the presence or absence of the template and investigate the cell association and biodistribution of these particles. An ex vivo assay based on human whole blood that is more sensitive and relevant than traditional cell-line based assays for predicting in vivo circulation behavior is introduced. The association of MS@PEG particles (template present) with granulocytes and monocytes is higher compared with PEG particles (template absent). Increasing the PEG molecular weight (from 10 to 40 kDa) or decreasing the PEG particle size (from 1400 to 150 nm) reduces phagocytic blood cell association of the PEG particles. Mice biodistribution studies show that the PEG particles exhibit extended circulation times (>12 h) compared with the MS@PEG particles and that the retention of smaller PEG particles (150 nm) in blood, when compared with larger PEG particles (>400 nm), is increased at least 4-fold at 12 h after injection. Our findings highlight the influence of unique aspects of polymer hydrogel particles on biological interactions. The reported PEG hydrogel particles represent a new class of polymer carriers with potential biomedical applications.