Versatile Polymeric Biomaterials

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The use of natural compounds can help to improve the biocompatibility and bioacceptance of polymeric biomaterials in their applications. Conjugating signaling agents for cellular recognition is of importance for such materials. We plan to design, synthesize and characterize new polymers containing moieties of natural biocompounds such as bile acids and saccharides and test them for their intended applications. Oligosaccharide units often serve as signaling agents in cellular membrane for the recognition of cells. Synthetic glycopolymers containing pendant saccharide moieties may be used as multivalent natural oligosaccharide mimics in biological and biomedical applications such as macromolecular drugs and drug delivery systems. We intend to systematically explore the use of glycopolymers with sugar residues designed for cellular interactions and targeted drug delivery. Living radical polymerization methods will be used to make block copolymers with bile acid unit in the more hydrophobic block and with sugar residues such as derivatives of glucosamine in the second block. The properties of such polymers will be studied and optimized for their intended applications. We have used anionic polymerization method to make block copolymers and would like to expand its use to make a variety of star-shaped copolymers and oligomers followed by functionalization of the end groups or the side groups by attaching glycol-residues/oligosaccharides for use in cellular recognition. In this case, we plan to use cholic acid, one of the major bile acids, as the core to initiate the polymerization and vary the length of the blocks to obtain copolymers with balanced amphiphilic properties. These polymers are expected to possess responsiveness to changes in temperature, pH and ionic strength and may be tested for use as biosensors and drug delivery vehicles. We would continue to explore the use of enzymes such as lipases in the preparation of degradable polymers through entropy-drive ring-opening polymerization of macrocyclic monomers derived from natural compounds. The use of enzymes can replace the use of catalysts based on heavy metals, ridding the polymers free of residual metals and thus making them more biocompatible. The polymers are known to be useful as shape-memory materials. Our recent discovery of the multiple-shape memory effect of such polymers will be further studied to optimize the molecular design of the polymers and to understand the structure-property relationship. This research work will help to build a library of new materials suitable for use in tissue engineering, bioseparation, biosensing and drug delivery. The characterization and physico-chemical study of the new polymers should provide an understanding of the properties of materials related to their chemical structures and compositions. The biocompatibility of some of the materials will be tested. The materials will be tested and optimized for their intended applications. We expect that the results obtained are useful and important to both fundamental and practical aspects of polymer chemistry and materials science. The interdisciplinary nature of the proposed work provides an ideal training environment for students in chemistry and biomaterials.