Hydrophilic polymers are the center of research emphasis in nanotechnology because of their perceived “intelligence”. They can be used as thin films, scaffolds, or nanoparticles in a wide range of biomedical and biological applications. Here we highlight recent developments in engineering uncrosslinked and crosslinked hydrophilic polymers for these applications. Natural, biohybrid, and synthetic hydrophilic polymers and hydrogels are analyzed and their thermodynamic responses are discussed. In addition, examples of the use of hydrogels for various therapeutic applications are given. We show how such systems’ intelligent behavior can be used in sensors, microarrays, and imaging. Finally, we outline challenges for the future in integrating hydrogels into biomedical applications.

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Hydrogels in Biology and Medicine: From Molecular Principles to Bionanotechnology†

Molecular imprinting within hydrogels.

Biomaterials are widely used in numerous medical applications. Chemical engineering has played a central role in this research and development. Polymers as biomaterials, materials and approaches used in drug and protein delivery systems, materials used as scaffolds in tissue engineering, and nanotechnology and microfabrication techniques applied to biomaterials are reviewed.

Advances in Biomaterials, Drug Delivery, and Bionanotechnology

Photopolymerization kinetics of multifunctional monomers

This work investigates the cytocompatibility of several photoinitiating systems for potential cell encapsulation applications. Both UV and visible light initiating schemes were examined. The UV photoinitiators included 2,2-dimethoxy-2-phenylacetophenone (Irgacure 651), 1-hydroxycyclohexyl phenyl ketone (Irgacure 184), 2-methyl-1-[4-(methylthio) phenyl]-2-(4-morpholinyl)-1-propanone (Irgacure 907), and 2-hydroxy-1-[4-(hydroxyethoxy)phenyl]-2-methyl-1-propanone (Darocur 2959). The visible light initiating systems included camphorquinone (CQ) with ethyl 4-N, N-dimethylaminobenzoate (4EDMAB) and triethanolamine (TEA) and the photosensitizer isopropyl thioxanthone. A cultured fibroblast cell line, NIH/3T3, was exposed to the photoinitiators at varying concentrations from 0.01% (w/w) to 0.1% (w/w) with and without the presence of initiating light. The results demonstrated that at low photoinitiator concentrations (6 0.01% (w/w)), all of the initiator molecules were cytocompatible with the exception of CQ, Irgac...

Cytocompatibility of UV and visible light photoinitiating systems on cultured NIH/3T3 fibroblasts in vitro

Highly crosslinked, PEG-containing copolymers for sustained solute delivery.

The kinetics of acrylic acid (AA) solution polymerizations were characterized under various polymerization conditions using differential scanning calorimetry. The AA polymerization rate R p decreased with increasing pH over all pH values due to the decreased reactivity of ionized AA relative to the unionized monomer. The rate behavior above pH 6 was suggestive of diffusion-controlled termination kinetics. The degree of ionization thus impacted not only the reactivity of species in solution but also the diffusive characteristics of propagating macroradicals. As the AA concentration was increased, the change in polymerization rate with pH was substantially less. The temperature dependence of R p indicated that the overall activation energy for polymerization varied with temperature, due to diffusion-controlled termination kinetics. The polymerization rate was significantly higher when a multifunctional cross-linking agent (trimethylolpropane triacrylate: TMPTA) was added, because of the gel effect, even while maintaining a constant double bond concentration.

Kinetic study of acrylic acid solution polymerization

Novel ionizable polymer networks were prepared from oligo(ethylene glycol) (OEG) multiacrylates and acrylic acid (AA), employing bulk radical photopolymerization techniques. The properties of these materials exhibit a complex dependence on the network structure and composition. Dynamic mechanical analysis and penetrant sorption experiments demonstrated that the cross-linked structure of the materials depends very strongly on the AA content, even in cases where the network chain population is expected to be composed solely of ethylene glycol oligomers. The results indicate that interchain interactions are diminished as the AA content is increased, due to the increased spatial separation of OEG chains. The compositional dependence of the glass transition temperature is qualitatively described by a treatment consistent with that employed for polymer blends, and deviations from ideal blend behavior point to the importance of system-specific free volume changes during the radical polymerization process. Hence,...

Compositional Effects on Network Structure of Highly Cross-Linked Copolymers of PEG-Containing Multiacrylates with Acrylic Acid

The kinetics of acrylic acid (AA) solution polymerization was investigated by polymerizing 30 wt % aqueous AA solutions at pH values ranging from 2.2 to 9.9. The polymerization rate was determined ...

Effects of ionization on the reaction behavior and kinetics of acrylic acid polymerizations

The compositional dependence of the polymerization kinetics of multiacrylate copolymers with acrylic acid (AA) was examined. The multiacrylates considered were di- or triacrylate esters of oligo(et...

Robert A. Scott

Papers

Highly crosslinked, PEG-containing copolymers for sustained solute delivery.

Kinetic study of acrylic acid solution polymerization

Compositional Effects on Network Structure of Highly Cross-Linked Copolymers of PEG-Containing Multiacrylates with Acrylic Acid

Effects of ionization on the reaction behavior and kinetics of acrylic acid polymerizations

Kinetics of Copolymerization of PEG-Containing Multiacrylates with Acrylic Acid