Mechanical Property And Drug Release Behavior Of PLA-based Composite Nanofibrous Materials

Electrospun nanofibers possess poor mechanical property due to high porosity,which limits their application in many fields. In the biomedical field, electrospun nanofibers as a good candidate of drug carrier, also needs to optimize their controlled drug release behavior. Poly(lactic acid)(PLA), as FDA-approved biopolymer, has used extensively in biomedical field due to its good biodegradability, biocompatibility and processability. In this study, the effect of addition of NDs on mechanical properties of electrospun PLA nanofiber was evaluated. Amphiphilic nanoparticles were used as stabilizers to prepare Pickering emulsion and electrospin it to drug loaded nanofibers with core-shell structure, to optimize the performance of controlled drug release. In addition, we hydrolyze beaded nanofibers to provide a new method for the preparation of polymer microspheres.Firstly, nanodiamonds(NDs) were employed for the first time to improve the mechanical properties of poly(lactic acid)(PLA)-based nanofiber scaffolds. Uniform ND/PLA composite nanofibers can be electrospun at <1 wt% loading of NDs. The introduction of NDs improved the thermal stability of PLA-based nanofibers. Fourier transform infrared spectroscopy results demonstrated good adhesion between ND nanofillers and PLA matrix. Following the addition of NDs, the four mechanical indicators, tensile strength, Young's modulus, elongation at break and fracture toughness of ND/PLA composite nanofiber membranes increases initially followed by later decrease with the rise of ND content. The four indicators achieved their respective maximum value at 1 wt% ND content, which represented 2.4-fold increase of tensile strength, 1.6-fold augment of Young's modulus, 1.4-fold elevation of elongation at break,4.8-fold growth of fracture toughness, respectively. By the standard of tensile strength and Young's modulus, NDs exhibited the best reinforcing ability for PLA-based composite nanofibers, which is attributed to the effective interfacial adhesion between PLA and rigid ND particles and good dispersion of NDs in PLA matrix. The ND/PLAcomposite nanofiber membranes with improved mechanical properties possess potential application in biomedical engineering.Secondly, in order to prepare a controlled drug release system without toxic side effects, we used amphiphilic nanoparticles as stabilizer to prepare Pickering emulsion and electrospun it to drug-loaded nanofibers with core-shell structure, to optimize the performance of controlled drug release. Amphiphilic magnetic ferroferric oxide nanoparticles(OA- MION) with oleic acid were prepared by co-precipitation. OA-MION were suspended in PLA solution by sonication followed by the dropwise addition of vancomycin to prepare W/O Pickering emulsion(PE), which were electrospun to acquire drug loaded nanofibers. The result of FTIR observation suggested that oleic acid was successfully adsorbed on the MION nanoparticles. Under 2 mg/ml of OA-MION,uniform distribution of the nanoparticles can be achieved on PE nanofibers, which posses a core-shell structure. For comparison, traditional emulsion(TE) nanofibers were prepared with the span 80 used as the stabilizer, PLA solution as the oil phase, and vancomycin as water phase. By comparing the results of drug release in vitro between the drug-loaded nanofibrous membrane made from the Pickering emulsion and the traditional emulsion, it was found that the drug release of Pickering emulsion was more slowly and the release lasted longer. The results showed that the nanofiber membrane made from PE possessed potential application as drug carrier.Finally, a new method to prepare nanospheres from electrospun beaded nanofibers was proposed. Taking into account the advantages of electrospinning, we prepared with beaded nanofibers and process under basic condition. By adjusting the parameters of electrospinning nanofibers, beaded nanofibers with different diameters were prepared.By changing the concentrations of sodium hydroxide solution and degradation time,microspheres with different diameters were obtained. SEM, XRD and DSC were employed to characterize the morphology and crystallinity of the hydrolyzed microspheres and the microsphere formation mechanism of hydrolyzing electrospun beaded nanofibers under alkaline conditions was also discussed.