Study On The Degradation Behavior Of Modified Polylactic Acid Scaffold And The Development Of Binary Drug-loading System

With the excellent biocompatibility and biodegradability,the polylactic acid(PLA)has been widely utilized in the biomedical applications of such as surgical sutures,drug sustained and controlled release delivery,tissue engineering,and cardiovascular stents.etc.In this research,PLA was chosen as the main biological material matrix,and the control of crystallinity of the PLA scaffold was achieved during the preparation of porous PLA scaffold by the modified solvent casting/particulate leaching method and the introduction of heat treatment process.In this way,the degradation behavior of the PLAscaffold can be regulated.Furthermore,the biocompatibility and hydrophilicity of PLA scaffold was improved through the physical blending modification with PEG,and the influence of the insertion the heat treatment process during the preparation of the scaffold on the crystallinity,thermal properties and degradation behavior of the blend scaffold were studied systematically.The results showed that the PLA and PEG in the blend scaffold experienced the phase separation during recrystallization,and the higher the PEG component content,the more serious phase separation.Based on this study,the porous(PLA)-(PLA-b-PEG)-(PEG)blend scaffold with a hydrophilic surface assembled by polyethylene glycol aggregations was prepared by the particle leaching/thermally induced phase separation method,where the PLA-b-PEG block polymer served as an amphiphilic glue between two components to avoid a total phase separation.In addition,the ASP/PEG-(PLA-b-PEG)-PLA/PTX complex drug-loading scaffolds were successfully prepared by chemical grafting.And the drug release results showed that,in the release process,the ASP bonded to PEG phase was firstly released,and lasted for 72 h,while the release rate of the drug PTX bonded to PLA phase was relatively slower,and the total release time was over 30 d.Finally,the three-layer drug complex films ASP/PTX-PLA simultaneously loaded with ASP and PTX was successfully prepared by the solution casting method and the drug in vitro release behavior of ASP/PTX-PLA was studied.The results showed that,as the early drug,ASP was released quickly in the early stage,and the accumulative release of drug in first 48 hours was close to 75%,while the PTX release in the whole stage was slow,and there was a time lag in the first stage.And the initial release time can be adjusted by changing the thickness of the outer membrane according to the actual needs.Two drugs with different pharmacological effects were successively released at different stages.Therefore,it provided a theoretical basis for the procedure drug delivery for therapy of restenosis after the percutaneous transluminal coronary angioplasty(PTCA).