Electrospun PLGA/gelatin Membranes And Biomimetic Mineralization On Their Surface

Electrospinning is an effective way to fabricate ultrafine fibers. With high specific surface area and high porosity, electrospun fibrous membranes can be used in tissue engineering. Electrospun membranes of synthetic and natural polymer blends combine the advantages of both, for example, the excellent tensile properties of the former and good biocompatibility of the latter. Electrospun membranes can be used as matrices of biomimetic mineralization to produce ceramic/polymer composite materials, which are able to mimic natural bone in the aspects of component and structure. In this study, highly porous electrospun membranes of PLGA/gelatin blends (PLGA/GEL) were used as matrices for the mineralization of synthetic Ca-P compounds in ten-time simulated body fluid (10SBF).Fibrous membranes of PLGA and PLGA/GEL with percentage of 1%, 5%, 10%, 15% were produced via electrospinning. The morphologies of ultrafine fibers were investigated by scanning electron microscope and transmission electron microscope. Studies on GEL released behaviors were processed by immerging PLGA/GEL membranes in fresh phosphate buffered saline (PBS). At the early stage, the burst releases of all membranes were obviously observed. After 1 d, the release percentages was 20%～30% and 21 d later, the final release percentages for PLGA/GEL membranes were nearly 75%-90%. PLGA/GEL membranes were crosslinked by glutaraldehyde (GA) under room temperature for 1 d. The water uptake and mechanical properties of PLGA and PLGA/GEL membranes before and after crosslinking were mensurated. The results showed that compared to PLGA membrane, the water uptake of PLGA/GEL membranes were increased due to the introduction of GEL component; however, crosslinking reduced the water uptakes of PLGA/GEL membranes. The mechanical properties of electrospun membranes were evaluated by tensile test, and the results indicated that the PLGA/GEL membranes with 1% or 5% GEL before crosslinking showed similar tensile strengthes and Young's moduli with PLGA membranes but higher elongation in dry state; after crosslinking every membranes had higher tensile strength and Young's modulus. Each membrane showed worse tensile properties in wet state than in dry state.The electrospun PLGA/GEL scaffolds were used as matrices for mineralization of calcium phosphate. The mineralization process could be initiated by immersing the electrospun scaffold in 10SBF for varying periods of time. Scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and Fourier transform infrared spectroscopy (IR) were used to characterize the compositions and the structures of the deposited minerals on the nanofiber surface. Results indicated that the mineral phases were inorganics with thin flake-like nanostructures or plate form of crystals. The results of EDS indicated that the Ca/P molar ratio of flake-like inorganic compound is 1.39, close to that of the octacalcium phosphate. While the Ca/P molar ratio in the plate compound of crystals is 0.92, close to that of the dicalcium phosphate dihydrate. From the spectra of IR, it can be seen that Phosphate vibrational band was present in the region of 660 and 520 cm-1, which confirmed the nucleation and growth of miners on the surface of PLGA/GEL. The minerals grew faster with the increase of the GEL amount, and with the release of GEL, the sets of nucleation moved to the surfaces of the fibers. Crosslinking by GA tended to inhibit calcium compound deposition on membranes.