Investigation Of In-vitro Degradation Properties Of Poly(lactide-co-glycolide) Gradient Films

PLGA, used as the carrier of drug, is wildly used in the area of biomedical industry not only for its good character of good biocompatibility and degradation, but also for its none toxic side effects degradation products. But it loses its mass rapidly during the end of the degradation. In order to improve the degradation character of PLGA coating, and avoid the phenomenon of centralized mass loss, we design the gradient structure which has steady degradation character.In the present work, we prepared the PLGA75:25 films, PLGA50:50 films, blend films, and gradient films by the method of pouring. The morphology, molecular weight, pH, mass loss, and water absorption of four types of PLGA films were analyzed during the process of degradation. The result shows that the PLGA film with gradient structure has the better degradation character. The result is significant to avoid the block in the blood vessel.Rapamycin as a drug, is commonly used in drug-eluting stents, and it can bind with binding protein (FKBP12) on the smooth muscle cells of vascular. Complexes formed after binding has a strong inhibition of (mTOR), leading to block of releasing and transcription of E2F which is in the vascular smooth muscle cells, which can inhibit proliferation and migration of smooth muscle cell effectively, therefore Rapamycin can inhibit restenosis after stent implantation.In this paper, we use hydrophobic drug Rapamycin as a model, Polylactide-glycolic acid as a carrier, and discuss the impact of drug releasing on degradation mechanism through analysis of samples of the drug releasing performance, and establish a specific mathematical model and test its legitimacy to provide a theoretical basis for the structural design for biodegradable drug delivery system in the future.