Enzymatic Synthesis And Property Investigaton Of Hyperbranched Polymer, Polyamino Acid

The use of enzyme in polymerization reaction, especially in the synthesis of hyperbranched polymers and polyamides, has been paid more and more attentions. Not only do enzymes acquire remarkable properties such as high selectivity and environmental acceptability, but also they have good biocompatibity. In this thesis, a methodology for enzyme-catalysis preparation of hyperbranched polymers was developed, which can be used in drug and gene delivery. Two types of chiral polymers poly-aspartic acid and poly-lysine were prepared by enzyme catalysis.Candida antarctica lipase B (CAL-B) was found to catalyze the polymerization of triethylolamine (TEOA) and diester, and five hyperbranched polymers were successfully prepared in this thesis. The influence of reaction conditions including the chain length of diesters, the ratios of two monomers, temperature and the concentration of enzyme were systematically investigated. Furthermore, we studied the structures of polymes by FTIR, GPC, ID and2D NMR techniques. The degree of branching (DB) was analysised and calculated in this thesis. The results show that through controling the feed ratios of monomer triethanolamine and diesters, the functional hyperbranched polymers with different terminal groups, which respectively are hydroxyl groups (DB=46.9%) and ester groups (DB=86.0%), can be effectively prepared.A series functions and properties of hyperbranched polymers were studied in this thesis, including their biodegradabilities, micellar self-assembly behaviors, cytotoxicities, tumor drug loading capacity, the abilities of forming DNA composite. The results show that this kind of hyperbranched polymers can be degraded in acidic environment under the catalysis of lipase. The amphiphilic polymers Poly(TEOA1-DMSE1) could be prepared when the monomer ratio is1:1, and self-assemble into micelles with particle size about250-400nm. The CAC of the micelles is0.042g/L. This kind of polymers showed non-toxic to COS-7. However, antitumor drug5’-O-vinyladipoyl-fluorodeoxyuridine loaded polymers could inhibit the growth of cancer cells HepG2, and the IC50value is130ug/mL. In addition, this kind of hyperbranched polymers had tertiary amine structures in its backbones, so it can form complexes with DNA for DNA’s transfer and release.Enzyme-catalyzed polymerization of aspartate and lysine was stydied in this thesis to form chiral poly(amino acid) polymers. Various enzymes were tested in this reaction, and we prepared chiral polymers directly using optically active monomers D-aspartic acid diesters and L-aspartic acid diesters. Polymer structures and the mode of connection were confirmed through the NMR characterization analysis. In addition, we prepared the chiral poly (L-lysine ethyl ester), and studied the selectivity of monomer configuration catalyzed by different enzymes. We also discussed the influence of the polymerization temperature and time.