温度响应的酶催化核交联胶束

Temperature-Responsive and Enzymatically Core-Crosslinked Micelles

以聚4-乙酰氧基苯乙烯P(4-ASt)和N-异丙基丙烯酰胺(NIPAm)为单体,通过可逆加成-断裂链转移聚合(RAFT)合成了结构明确窄相对分子质量分布(M_w/M_n=1.28)的两嵌段共聚物P(4-ASt-b-NIPAm)。通过水合肼将P(4-ASt-b-NIPAm)中的P(4-ASt)嵌段上的乙酰基团选择性水解后得到聚(4-乙烯基苯酚-b-N-异丙基丙烯酰胺)两嵌段共聚物P(4-VPh-b-NIPAm)。采用~1HNMR、FTIR和GPC对P(4-VPh-b-NIPAm)结构进行了表征,利用荧光光谱、透光率法和DLS研究了其水溶液的聚集行为和温度响应性。结果表明,P(4-VPh-b-NIPAm)在水中可自组装形成以P(4-VPh)为核、PNIPAm为壳的胶束,其临界胶束浓度(CMC)为0.015 g/L,室温下平均粒径约为137 nm,低临界溶解温度(LCST)为31.2℃。以辣根过氧化物酶(HRP)催化交联P(4-VPh)核制备了平均粒径约为119 nm的核交联胶束,TEM显示干态核交联胶束为球形,粒径为60~100 nm。核交联胶束水溶液具有良好的热稳定性和温度响应性,其相转变温度为32~36℃,LCST约为34.9℃,随温度升高平均粒径从25℃的119 nm减小至37℃的92.9nm。

Diblock copolymer P(4-ASt-b-NIPAm)with well-defined structure and narrow molecular-weight distribution(M_w/M_n=1.28)was synthesized by reversible addition-fragmentation transfer(RAFT)polymerization using poly(4-acetoxystyrene)P(4-ASt)and N-isopropylacrylamide(NIPAm)as monomers.The acetyl groups in the chain of P(4-ASt-b-NIPAm)were selectively hydrolyzed by hydrazine hydrate to obtain diblock copolymer P(4-VPh-b-NIPAm).Copolymer P(4-VPh-b-NIPAm)was characterized by^1HNMR,FTIR and GPC.The aggregation behavior and temperature response of P(4-VPh-b-NIPAm)aqueous solution were studied by fluorescence spectrum,transmittance method and DLS.The results showed that copolymer P(VPh-b-NIPAm)could self-assemble into micelles using P(4-VPh)as core and PNIPAm as shell in aqueous solution and the critical micelle concentration(CMC)was 0.015 g/L.The average particle size was about 137 nm at room temperature and the lower critical solution temperature(LCST)was 31.2℃.Horseradish peroxidase(HRP)catalyzed cross-linking of P(4-VPh)core to prepare core-crosslinked micelles with an average particle size of 119 nm.TEM showed that dry core-crosslinked micelles were spherical with particle size of 60~100 nm.The aqueous solution of core-crosslinked micelles had good stability and temperature response.Its phase transition temperature ranged from 32℃to 36℃and its LCST was about 34.9℃.The average diameter of core-crosslinked micelles decreased from119 nm to 92.9 nm with increasing temperature from 25℃to 37℃.