Preparation And Characterization Of Carboxybetaine Zwitterionic Polymer

Protein-resistant materials are very important in applications such as biomedicine, marine coating, biochip etc. It has been a hot research topic. It is found that some zwitterionic polymers possess excellent protein-resistant performance.The molecular structure and synthetic route of one novel carboxybetaine zwitterionic monomer were designed based on structure-activity relationship, in terms of antifouling theory and requirements of the products'application. Taking 3-acrylamido- N,N-dimethypropylamine (DMAPAA) as the raw material, one novel carboxybetaine zwitterionic monomer, 1-Carboxy-N,N-dimethyl-N-(3-acrylamidopropyl) ethanaminium inner salt (CBAA-1), was obtained by quaternization reaction with sodium chloroacetate (ClCH₂COONa). IR spectral analysis was employed to confirm the structure of the monomer. An optimum reaction condition for the preparation of CBAA-1 monomer was found: water works as the solvent; the molar ratio of DMAPAA and ClCH₂COONa is 1:1.05; reaction temperature is 70°C and reaction time is 5 hours, the conversion rate of tertiary amine reaches 98.5%.CBAA-1 zwitterionic monomer was polymerized to obtain carboxybetaine zwitterionic polymers p(CBAA-1) through solution polymerization. IR spectral analysis was used to confirm the structures of the synthesized polymer. Optimum reaction condition to synthesize p(CBAA-1) by static contact angle measurement of p(CBAA-1) was found: the concentration of monomer is 20%, the concentration of initiator is 0.8% of that of the monomer; reaction temperature is 50°C and reaction time is 6 hours, the static contact angle reaches 44°, carboxybetaine zwitterionic polymers p(CBAA-1) show the best hydrophilicity.Surface Plasmon Resonance was used to characterize carboxybetaine zwitterionic polymers p(CBAA-1)'s protein-resistant performance. Both positively-charged and negatively-charged self-assembled monolayers (SAMs) were prepared on the gold surface. Through electrostatic adsorption, carboxybetaine zwitterionic polymers p(CBAA-1) were adsorbed at positively-charged NH2-SAM and negatively-charged COOH-SAM respectively and then decorated with immobilized albumin. SPR instrumentation characterized the adsorption of fibrinogen. The experimental results showed that, p(CBAA-1) adsorbed on negatively-charged COOH-SAMs shows better protein adsorption resistant ability and better ability to immobilize albumin. After the immobilization of albumin, p(CBAA-1)'s protein -resistance ability increases greatly.