Study On Synthisis And Properties Of Glucose-Responsive System With Polypeptide Block And Sans Study On Structures Of Glucose-Responsive System

This thesis was aimed at improving the salt tolerance of PBE-based glucose-responsive system. Polypeptide block was introduced into complex nanoparticles through co-assembling with the glucose-responsive copolymer, in order to develop the stability, glucose concentration selectivity and biocompatibility of the PBE-based system. Polypeptide is one of the most biocompatible and biodegradable materials with unique secondary structures which provide potential applications with their self-assembled structures. In addition, to give an insight to the structures and glucose-responsive mechanism of the PBE-based system, we used small angle neutron scattering (SANS) to study structures of nanoparticles assembling from PBE-containing copolymers.1. Introducing polypeptide into the PBE-based glucose-responsive system via co-assembling. First, we obtained mPEG5000-b-PBLG with narrow molecular weight distribution through living and well-controlled ring-opening polymerization of NCAs followed with characterization of NMR and GPC. mPEG5000-b-PPBDEMA with proper CMC was chosen to co-assemble with mPEG5000-b-PBLG. Complex nanoparticles with different contents of mPEG5000-b-PBLG were developed and characterized by DLS, TEM and CD. These nanoparticles possess uniform size and a-helix. After studying salt tolerance ability of these complex nanoparticles, we studied glucose-responsive behavior of the chosen nanoparticles which were the most stable in physiological conditions (0.15 M PBS, pH 7.4). The results showed that the complex narnaparticles have good selectivity about glucose concentrations and stimuli-responsivity in a certain period of time. What's more, the encapsulating ability and biocompatibility were improved at the same time.2. SANS was used to study the structure of PBE-based nanoparticles, founding that the structure changed with the change of PEG content in the copolymer, glucose concentration, pH and the PBS concentration. SANS data showed that mPEG-b-PPBDEMA with 24 wt.% PEG self-assembled into vesicle while mPEG-b-PPBDEMA with 64 wt.% PEG self-assembled into slender micelles which can be fitted with ellipsoids or cylindrers. Changes occurred in structure of either vesicles or ellipsoids or cylindrers after addition of glucose or NaOD, or change of PBS concentration. Results from this paper have provided important insights into nanostructures formed by PBE-based glucose-responsive block copolymers and the mechanism of their responses to glucose, pH, and ionic strength.