两亲性壳聚糖衍生物的制备及其包覆量子点

SYNTHESIS OF AMPHIPHILIC CHITOSAN DERIVATIVES AND THEIR APPLICATION IN ENCAPSULATION OF QDs

以天然壳聚糖为功能性高分子的骨架,通过西弗碱还原法,以正辛醛和端醛基聚乙二醇单甲基醚(mPEG aldehyde,mPEG-ald)修饰壳聚糖,制备了具有亲疏水性质的N-辛基化-N-mPEG化壳聚糖衍生物(N-octyl-N-mPEG-chitosan,OPEGC),并且以此两亲性壳聚糖衍生物包覆量子点制备了水溶性聚合物量子点纳米粒子.用FTIR、1H-NMR对壳聚糖衍生物进行了结构表征.制备的水溶性胶束,用动态光散射(DLS)测试其流体力学直径与分布,研究了烷基链接枝比率对粒径大小的影响,研究结果表明:烷基链接枝率越高,聚合物胶束粒径越小.以芘为分子探针,通过荧光光谱法测定了壳聚糖衍生物的临界胶束浓度(CMC)为2.032×10-2mg/mL,并对水溶性聚合物量子点纳米粒子进行了紫外、荧光及形貌表征,结果表明得到了荧光发射产率高的聚合物量子点纳米粒子,且尺寸均一、水溶性好.

Amphiphilic chitosan derivatives（N-octyl-N-mPEG-chitosan,OPEGC）were successfully synthesized via sequential Schiff base reduction reaction of chitosan with mPEG-aldehyde and n-octanal,with chitosan acting as the backbone of the grafted copolymers,and mPEG-aldehyde providing hydrophilic chain and n-octanal providing hydrophobic alkyl chain,respectively,thereby hydrophobic moiety inclining to segregate into the core of the polymeric micelles,while hydrophilic moiety forming a stabilizing interface between the hydrophobic core and the external medium.The structure of grafted copolymers with both hydrophilic and hydrophobic composition simultaneously was confirmed by characterization employing FTIR and 1H-NMR.In the subsequent procedure,water-soluble quantum dots（QDs）,widely used as nanoprobe for medical application,were achieved by incorporation of QDs inside the polymeric micelle core through the hydrophobic interaction between the acyl chain ligand capped on the QDs and the hydrophobic inner core of the polymeric micelles.The size and distribution of the polymeric micelle was determined by dynamic light scattering（DLS）,as well the effect of the amount of alkyl chains on the size of the hollow polymeric micelles.The result showed that with grafting level increasing,the size of these nanoparticles diminished accordingly.Moreover,critical micelle concentration（CMC） was determined based on I3/I1 derived from emission spectrum afforded by fluorescence spectroscopy with pyrene as fluorescent probe,with the value of CMC 2.032×10-2mg/mL.At last,the optical properties of OPEGC/QDs were characterized by UV-Vis spectroscopy,fluorescence spectroscopy and the morphology of their assembly formed in water was observed by TEM.The results indicated that the OPEGC/QDs nanoparticles with narrow size distribution were prepared here,which represented good water solubility and high quantum yield.