Synthesis Of Polylactide/Methoxy Polyethylene Glycol Block Copolymer And Its Application In Tissue Engineering As Drug Delivery System

In this thesis, the amphiphilic block copolymer methoxy polyethylene glycol-b-poly(L-lactide) (PELA) and methoxy polyethylene glycol-b-poly -(D,L-lactide) (PEDLA) were prepared by melting polymerization in the presence of stannous 2-ethyl hexanoate(Sn(Oct)2). The chain compositions of the copolymers were characterized by IR and 1H-NMR. Molecular weight and polydispersity index, thermal properties and crystalinity were determined byGPC, DSC and XRD. The results showed that the structure and molecular weight of obtained copolymers were basically in accord with pre-design, their ctystallization degree were decreased as the molecular weight increasing.The amphiphilic block copolymer self-assembly micelles and phen-loaded micelles were obtained by the method of self-emulsification solvent evaporating. Their particle size were determined by DLS. The influences of pH value of the medium and the structure of the copolymers on micelle size were investigated. The CMC of the copolymer and drug encapsulation were decided by UV-visible spectrophotometer. It was clearly showed that the micelle had an apparent core structure and narrow distribution. The CMC decreased as the increasing of polymer molecular weight. For PEDLA12.5(1)-phen, its biggest encapsulation could reach to 80.94% . Drug release test showed that it had no obvious release-burst and phen completely released 25h later.Mixing Ted-loaded PELA micelle(PELA-Ted) with chitosan-gel solution and then freeze-drying, could obtain three-dimensional porous scaffold load PELA-Ted micelle (CS-Gel-PELA-Ted). The inner morphology of the scaffold,and pore size were observed by Scanning Electron Microscope(SEM). The scaffold's mechanical properties were tested by compression test. The results showed that the scaffolds had high porosity, and combination of PELA micelle could strengthen the scaffold toughness. The sustained release of tetrandrine from the scaffolds in vitro was also studied. The drug delivery behavior was assayed by high-performance liquid chromatography. It was found that drug release was effectively controlled by the drug encapsulation.