Preparation And Properties Of Thermo-sensitive PLEAA与PALA Materials

Temperature-sensitive polymer is a kind of material which can make fast response to temperature change. In the vicinity of the critical temperature, intramolecular and intermolecular interactions of amphiphilic polymers are changed, and the polymer micelles have a reversible phase transition of "gathered-dissolution". With the excellent performance, thermo-sensitive polymer can have broad application prospects in drug release and tissue repair and other medical fields. Due to the applications in the medical field, good biocompatibility is an inevitable requirement for thermo-sensitive polymers. In this study, by the combination of natural amino-acid and lactic acid, the thermo-sensitive polymer with good biocompatibility has been prepared. Three parts are included in this paper:The first part is the literature review and it includes the introduction of intelligent polymer materials, synthesis, characterization and application of thermo-responsive polymer.Second, good biocompatibility or no cytotoxicity is the most important characteristics for thermo-sensitive polymeric material because of its potential applications in the biomedical field. In this paper, a new poly(lysine ester-co-adipic acid)s(PLEAA) with both thermo-sensitivity and excellent biocompatibility was designed and successfully prepared in the solution polycondensation. The chemical structure of the monomers and PLEAA were characterized by FTIR, 1H NMR and GPC measurements. The UV measurements have indicated that the lower critical solution temperature(LCST) of PLA was found in the range of 0.5-33.7 ℃, and affected by molecular weight, structure and concentration. Moreover, the viability of He La cells after 24 h incubation in PLEAA solution reached up to 98%-133%, suggesting its excellent biocompatibility. In summary, the new thermo-sensitive PLEAA with no cytotoxicity could be utilized as a promising bio-material in the biomedical field.Third, as an important biomaterial, poly(L-lactic acid) and poly(L-alanine) have good biodegradability and biodegradability. According to the mechanism of thermo-sensitivity, a series of poly(L-lactic acid-co-L-alanine)s with different structure unit have been synthesized under the assistance of microwave from natural L-lactic acid and L-alanine monomer. When the ratio of L-lactic acid to L-alanine unit in the polymer chains was 0.9:1.0-0.6:1.0, the prepared polymer showed a reversible thermo-sensitivity, and LCST was found to be about 37℃. The polymer structure has a dependence on condition of the polymerization and feed ratio of the monomers in the experiment. Additionally, the high viability of He La cells by MTT assay was determined as 100% at the concentrations up to 1mg/m L, indicating no detectable cytotoxicity of poly(L-lactic acid-co-L-alanine). In conclusion, the novel thermo-sensitive poly(L-lactic acid-co-L-alanine) with good biocompatibility can be a promising material in the biomedical field.