Key Laboratory of Polymer Ecomaterials, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, PR China.
J Colloid Interface Sci. 2011 Jul 15;359(2):436-42. doi: 10.1016/j.jcis.2011.04.037. Epub 2011 Apr 18.
A polypeptide-based double hydrophilic graft copolymer was synthesized by the sequential grafting of poly(N-isopropylacrylamide) (PNIPAM) and 2-hydroxyethyl methacrylate (HEMA) onto poly(l-glutamic acid) (PGA) backbone. The copolymers were sensitive to both temperature and pH. The phase transition and aggregation behaviors of the graft copolymers in aqueous solutions were investigated by the turbidity measurements and dynamic laser scattering (DLS). The light transmittance decrease of the copolymers at temperature above lower critical solution temperature (LCST) was remarkably weakened at pH around 6.5 due to the coil to α helix change of PGA chain induced by pH. The copolymers can self-assembly into micelles with PNIPAM cores in the aqueous solution at pH 8.0 and 60°C. Subsequently, polymerization of HEMA led to the facile preparation of crosslinked micelles, which were observed directly by transmission electron microscopy (TEM). The temperature controlled shrinkage behaviors of crosslinked micelles highly depended on the pH values of the solution. The crosslinked micelles aggregated at pH 5.0 due to the increased hydrophobic interactions among them induced by the protonation of PGA component. These crosslinked micelles have promising applications as intelligent drug delivery vehicles.
一种基于多肽的双亲性接枝共聚物是通过聚（N-异丙基丙烯酰胺）（PNIPAM）和 2-羟乙基甲基丙烯酸酯（HEMA）在聚（L-谷氨酸）（PGA）主链上的顺序接枝合成的。共聚物对温度和 pH 值均敏感。通过浊度测量和动态激光散射（DLS）研究了接枝共聚物在水溶液中的相转变和聚集行为。由于 pH 值引起 PGA 链的构象从无规线团到α-螺旋的转变，共聚物在高于低临界溶液温度（LCST）的温度下的光透过率降低在 pH 值约为 6.5 时显著减弱。共聚物在 pH 8.0 和 60°C 的水溶液中可以自组装成具有 PNIPAM 核的胶束。随后，在 HEMA 的聚合作用下，很容易制备出交联胶束，这可以通过透射电子显微镜（TEM）直接观察到。交联胶束的温度控制收缩行为高度依赖于溶液的 pH 值。由于 PGA 组分的质子化引起的疏水性相互作用增加，交联胶束在 pH 值为 5.0 时聚集。这些交联胶束有望作为智能药物输送载体得到应用。
