Green Chemistry Approach in Developing Polymeric Biomaterials

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Given the importance and growing concerns of environmental protection and energy consumption, biotechnology holds the key for chemical industry and sustainable development in the future. We use green chemistry approaches to make biocompatible materials to solve related problems. (1) New biomaterials. Biocompatibility is important for polymers used for biomedical and pharmaceutical applications in contact with the human body. To address this issue, we use natural compounds (bile acids, carbohydrates, amino acids) from biological sources in the design and synthesis of a variety of polymers, including degradable polymers, stimuli-responsive materials, self-healing hydrogels. The polymers will be characterized and tested for their intended applications including soft and hard tissue engineering, drug delivery and cell culture. Bio-functional groups will be introduced in the polymers for molecular and cellular recognition in targeted delivery of drugs and for the design and tests of biosensors. The biocompatibility and toxicity of the materials will be studied. (2) Green chemistry methods will be developed for the synthesis and modification of polymers. Enzymes will be used in the transformation of the biomolecules already attached on a polymer chain to produce functional groups with new properties. For example, glucose oxidase will be tested to convert the carbohydrate side groups attached on our sugar-containing polymers into acid groups. Such a copolymer may be pH-responsive, and the charged carboxylic group will also facilitate biomineralization needed for bone regeneration. Our preliminary results are encouraging, and we will study the efficiency of enzymes in the transformation of the different substrates on the polymers. Enzymes such as nitrile hydratase, nitrilase and amidase will be used in the transformation of the nitrile groups into amide and then into acid groups, thereby simplifying the synthetic procedure of copolymers and avoiding the use of metal catalysts and stringent reaction conditions. The thermoresponsiveness and solution properties of these polymers will be studied to explore their applications as flocculants and rheology-modifiers. (3) Molecular hydrogelation. Bile acid derivatives are found to form molecular hydrogels through supramolecular assembly. We have demonstrated that a marginal solubility achieved through molecular interactions is a condition for the gelation of small molecules. We will try to elucidate the principles guiding the hydrogelation process. The rheological and mechanical properties of the gels will be studied and their use in cell culture and soft-tissue engineering will be tested. In summary, the proposed research work is of both fundamental and practical importance and will lead to innovative technology and new functional materials for biomedical and industrial applications. It is multi-disciplinary in nature and will provide an ideal training environment for young highly qualified personnel.