Study On Ultrafine PVA Fiber Mat Prepared By Electrospinning And Its Application In Drug Delivery System

Electrospinning is a process that produces polymer fibers with diameter in the sub-micron range under the action of an external electric field imposed on a polymer solution or melt. Nonwoven membranes composed of electrospun fibers have a large specific surface area and small pore size compared to commercial textiles, making them excellent candidates for filters, nanocomposites, wound dressings and engineering scaffolds. In this work, submicron polyvinyl alcohol (PVA) fiber mats were prepared by electrospinning aqueous PVA solution with 6wt%-8wt% concentration. Fiber morphology was observed under scanning electron microscope, transmission electron microscope and atomic force microscope. It was found that, when PVA with 98 mol %, high degree of hydrolysis , was used in electrospinning, tip-target distance and solution feed rate had no significant effects on fiber diameter. With high voltage above 10 kV, PVA fibers exhibited a broad diameter distribution. With increasing solution concentration, the morphology was changed from beaded fiber to uniform fiber and the average fiber diameter could be increased from 87 nm to 246 nm. It was also found addition of ethanol and salt had obvious effects on the fiber diameter and morphology of electrospun PVA fibers because of the different solution conductivity, surface tension and viscosity. More bonded fiber structures were found for partially hydrolyzed PVA. The morphology was changed from ribbonlike fibers to uniform fibers and then to beaded fibers when the hydrolysis degree of PVA increased from 80% to 99% gradually. Fourier transformed infra-red spectra and X-ray photoelectron spectroscopy of PVA fiber mat showed that electrospinning process brought no changes to PVA chemical structure. Evaluation of microstructure by X-ray diffraction showed poor development of crystalline in electrospun PVA fiber mats. According to differential scanning calorimetry thermal analysis, the degree of crystallinity of the electrospun PVA fiber mat was only 34%, significantly lower than that of casting film (45 %) but slightly higher than PVA commercial powder (30%), and increased to 40 % after annealing at 90℃for 1 h. The tensile strength, young's modulus and strain at break of PVA fiber mat were 5.10±0.77 MPa, 236±27 MPa and 8.28±2.38% respectively, indicating poor mechanical properties compared with PVA casting film. Water absorbency of PVA fiber mats were more than 300%, higher than that of PVA casting film. PVA fiber mats were explored as drug delivery vehicles using aspirin and bovine serum albumin (BSA) as model drugs. They were prepared by electrospinning aqueous PVA solution containing the drugs. Release profiles of aspirin and BSA from the electrospun fiber mat were completely different from the same drug delivery systems made from PVA casting film.