Chemical and Biomolecular Engineering - Research Publications
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ItemFabrication of Chiral Stationary Phases via Continuous Assembly of Polymers for Resolution of Enantiomers by Liquid Chromatography(WILEY-V C H VERLAG GMBH, 2014-11)Precise stereochemical determination of chiral molecules is highly important, especially in the pharmaceutical industry where one enantiomer may have a therapeutic effect while the other has detrimental effects. Herein, the continuous assembly of polymers (CAP) mediated via ring‐opening metathesis polymerization (ROMP) is used to fabricate immobilized‐type chiral stationary phases (CSPs) – as cross‐linked thin films on solid supports – for enantiomeric separation. Optically active polysaccharides (chitosan and amylose) with aromatic substituents were pre‐functionalized with pendent norbornene groups and subsequently employed as macrocross‐linkers in the CAPROMP process, building cross‐linked films from initiator‐functionalized mesoporous silica particles. The immobilized cross‐linked films on mesoporous silica particles can act as CSPs. Therefore, the chiral recognition abilities of the CSPs were explored by liquid chromatography (LC). It was found that CSPs with higher amount of polysaccharide cross‐linked films – made from multiple CAP reactions – have better chiral separation capabilities. This work demonstrates the versatility of the CAP approach to fabricate CSPs to tailor specific separation needs.
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ItemNo Preview AvailableContinuous assembly of polymers via solid phase reactions(ROYAL SOC CHEMISTRY, 2014-09)
The formation of cross-linked polymer films, with tunable thickness, proceeds directionally from the substrate surface by controlled polymerization in the solid state.
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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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ItemLysine functionalised amyloid fibrils: the design and assembly of a TTR1-based peptide(ROYAL SOC CHEMISTRY, 2013)
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ItemLayer-by-Layer Polymer Coating on Discrete Particles of Cubic Lyotropic Liquid Crystalline Dispersions (Cubosomes)(AMER CHEMICAL SOC, 2013-10-22)Cubic phase lyotropic liquid crystalline colloidal dispersions (cubosomes) were surface-modified with seven polyelectrolyte layers using a layer-by-layer (LbL) approach. The first layer consisted of a copolymer synthesized from methacrylic acid and oleoyl methacrylate for enhanced incorporation within the bilayer of the cubic nanostructure. Six additional layers of poly(L-lysine) and poly(methacrylic acid) were then sequentially added, followed by a washing procedure to remove polymer aggregates from the soft matter particles. Polymer buildup was monitored via microelectrophoresis, dynamic light scattering, and small-angle X-ray scattering. Polymer-coated cubosomes were observed with cryo-transmission electron microscopy. A potential application of the modified nanostructured particles presented in this study is to reduce the burst-release effect associated with drug-loaded cubosomes. The effectiveness of this approach was demonstrated through loading and release results from a model hydrophilic small molecule (fluorescein).
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ItemA Cytoprotective and Degradable Metal-Polyphenol Nanoshell for Single-Cell Encapsulation(WILEY-V C H VERLAG GMBH, 2014-11-10)Single-cell encapsulation promises the cytoprotection of the encased cells against lethal stressors, reminiscent of the sporulation process in nature. However, the development of a cytocompatible method for chemically mimicking the germination process (i.e., shell degradation on-demand) has been elusive, despite the shell degradation being pivotal for the practical use of functional cells as well as for single cell-based biology. We report that an artificial shell, composed of tannic acid (TA) and Fe(III) , on individual Saccharomyces cerevisiae controllably degrades on-demand, while protecting the yeast from multiple external aggressors, including UV-C irradiation, lytic enzymes, and silver nanoparticles. Cell division is suppressed by the TA-Fe(III) shell, but restored fully upon shell degradation. The formation of a TA-Fe(III) shell would provide a versatile tool for achieving the chemical version of "sporulation and germination".
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ItemLow-Fouling, Biospecific Films Prepared by the Continuous Assembly of Polymers(AMER CHEMICAL SOC, 2013-08)We report that the continuous assembly of polymers (CAP) approach, mediated by ring-opening metathesis polymerization (ROMP), is a facile and versatile technology to prepare engineered nanocoatings for various biomedical applications. Low-fouling coatings on particles were obtained by the formation of multicompositional, layered films via simple and efficient tandem CAP(ROMP) processes that are analogous to chain extension reactions. In addition, the CAP(ROMP) approach allows for the efficient postfunctionalization of the CAP films with bioactive moieties via cross-metathesis reactions between the surface-immobilized catalysts and symmetrical alkene derivatives. The combined features of the CAP(ROMP) approach (i.e., versatile polymer selection and facile functionalization) allow for the fabrication and surface modification of various types of polymer films, including those with intrinsic protein-repellent properties and selective protein recognition capabilities. This study highlights the various types of advanced coatings and materials that the CAP approach can be used to generate, which may be useful for biomedical applications.
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ItemStiffness-mediated adhesion of cervical cancer cells to soft hydrogel films(ROYAL SOC CHEMISTRY, 2013)
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ItemTuning the Mechanical Properties of Nanoporous Hydrogel Particles via Polymer Cross-Linking(AMER CHEMICAL SOC, 2013-08-06)Soft hydrogel particles with tunable mechanical properties are promising for next-generation therapeutic applications. This is due to the increasingly proven role that physicochemical properties play in particulate-based delivery vectors, both in vitro and in vivo. The ability to understand and quantify the mechanical properties of such systems is therefore essential to optimize function and performance. We report control over the mechanical properties of poly(methacrylic acid) (PMA) hydrogel particles based on a mesoporous silica templating method. The mechanical properties of the obtained particles can be finely tuned through variation of the cross-linker concentration, which is hereby quantified using a cross-linking polymer with a fluorescent tag. We demonstrate that the mechanical properties of the particles can be elucidated using an atomic force microscopy (AFM) force spectroscopy method, which additionally allows for the study of hydrogel material properties at the nanoscale through high-resolution force mapping. Young's modulus and stiffness of the particles were tuned between 0.04 and 2.53 MPa and between 1.6 and 28.4 mN m(-1), respectively, through control over the cross-linker concentration. The relationship between the concentration of the cross-linker added and the amount of adsorbed polymer was observed to follow a Langmuir isotherm, and this relationship was found to correlate linearly with the particle mechanical properties.
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ItemNear-Incompressible Faceted Polymer Microcapsules from Metal-Organic Framework Templates(WILEY-V C H VERLAG GMBH, 2013-10)Faceted polymer microcapsules are prepared from metal-organic framework (MOF) templates. The MOF templates are removable under mild aqueous conditions. The obtained microcapsules are stiffer than their spherical counterparts, reflecting the near-incompressibility of the facet edges, and indicating that the faceting might be a useful strategy for controlling the mechanical properties of polymer microcapsules.