温度响应的酶催化核交联胶束

Enzymatically Temperature-Responsive Core-Crosslinked Micelle

摘要:

以对乙酰氧基苯乙烯（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(Mw/Mn=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（P4-VPh）为核、PNIPAm为壳的胶束，其临界胶束浓度（CMC）为0.015g/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60~100nm。核交联胶束水溶液具有良好的稳定性和温度响应性，其相转变温度范围为32~36℃，LCST约为34.9℃，随温度升高平均粒径从25℃的119nm减小至37℃的92.9nm。

Abstract:

Diblock copolymer P(4-ASt-b-NIPAm) with well-defined structure and narrow molecular-weight distri-bution (Mw/Mn=1.28) was synthesized by reversible addition-fragmentation transfer (RAFT) polymeriza-tion using poly(4-acetoxystyrene) P(4-ASt) and N-isopropylacrylamide (NIPAm) as monomers. The ace-tyl 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 solu-tion were studied by fluorescence spectrum, transmittance method and DLS. The results showed that co-polymer 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 parti-cle 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 mi-celles 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 from 119 nm to 93 nm with increasing temperature from 25℃ to 37℃.