Biodegradable Shape-memory Polyester Networks And Application In Drug Controlled Release

Biodegradable shape-memory polymers have been extensively investigated, which have excellent properties, such as good mechanical properties, and multifunctionalities, etc. They have drawn increasing attention as their potential applications for medical materials, such as surgical sutures, drug delivery carriers and scaffolds, etc. In this thesis, several kinds of biodegradable polyurethanes or polyesters with good shape-memory effect are synthesized. The degradation and drug release behaviors of these biodegradable networks are also studied.Star-shaped oligo[(D,L-lactide)-co-glycolide] (PLGA) with different number-average molecular weights and glycolide content is synthesized through ring-opening polymerization of D,L-lactide and glycolide with dibutyl tin oxide (DBTO) or Stannous octoate (Sn(oct)2) as catalyst and pentaerythritol as an initiator. The obtained oligomers are characterized by hydroxy titration, Fourier transform infrared spectrometry (FTIR), gel permeation chromatography (GPC) and 1H proton nuclear magnetic resonance (1HNMR).Biodegradable, amorphous polyesterurethanes (PU) are synthesized by the coupling reaction of PLGA and diisocyanate, which have good shape-memory and mechanical properties. But the hydrophilicity and toughness are very poor. The transition temperatures (Ttrans) of PU can be adjusted by changing the molecular weights and compositions of the PLGA.Polyesterurethane/poly(ethylene glycol) dimethacrylate (PEGDMA) interpenetrating networks materials (IPNs) with shape-memory properties are synthesized. The hydrophilicity and transition temperatures of IPNs can be conveniently adjusted through variation of network compositions to match the promising potential clinical or medical applications.Poly[(D,L-lactide)-co-glycolide] tetracrylate (PLGATA) is synthesized by PLGA and acrylic chloride. Shape-memory polyester materials (LP) are obtained through photopolymerization of PLGATA and PEGDMA. The hydrophilicity and Ttrans of LP can be conveniently adjusted.The degradation behavior of the PU is investigated in PBS solution. The degradation process can be approximately divided into two phases: the induction course and the acceleration course. The water uptake and weight loss of PU samples increase slowly in the induction course and increase significantly in acceleration course.The release behavior of model drug aspirin (ASP) and dexamethasone (DEX) from biodegradable polyesterurethane networks is also studied. The release result exhibits a typical erosion-controlled release mechanism, which is combined effect of degradation and diffusion. The drug release course of ASP from PU networks is shorter than from DEX for the acidity of ASP. The release course of ASP last about 20 days and it is 120 days for DEX. The degradation course of drug-loaded materials is accelerated faster than those of drug-free materials.