No abstract

Biodegradable materials are widely used in the biomedical field because there is no postoperative surgery after implantation. Widely used synthetic biodegradable materials are polyesters, especially those used in tissue engineering. Advances in the tissue engineering field have brought much attention in terms of scaffold fabrication, such as with biodegradable polyester nanofibers. The rationale for using nanofibers for tissue engineering is that the nonwoven polymeric meshwork is a close representation of the nanoscale protein fiber meshwork in native extracellular matrix (ECM). Electrospinning technique is a promising way to fabricate controllable continuous nanofiber scaffold mimicking the ECM structure. Electrospun nanofibers provide high surface-to-volume ratio and high porosity as a promising scaffold for tissue engineering. Because the degradation behaviors of scaffolds significantly affect new tissue regeneration, the degradation of the material becomes one of the crucial factors when considering using polyester nanofibers as scaffolds in tissue engineering. In this review paper, we focus on the degradation studies of several bioresorbable polyester nanofibrous scaffolds used in tissue engineering. The degradable properties of nanofibers were compared with the corresponding degradable materials in macroscale. The factors that might affect the degradation behaviors were analyzed.

Poly-L-lactic acid (PLLA) and PLLA/collagen (50% PLLA+50% collagen; PLLA/Col) nanofibers were fabricated using electrospinning. Mineralization of these nanofibers was processed using a modified alternating soaking method. The structural properties and morphologies of mineralized PLLA and PLLA/Col nanofibers were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and contact angle measurements. Human bone-derived osteoblasts were cultured on the materials for up to 1 week to assess the biological properties of the nanofibrous composites. Cell attachment on these nanocomposites was also tested within 1 h of culture at room temperature. The mechanical properties of the cell-nanocomposite constructs were determined using tensile testing. From our results, the bone-like nano-hydroxyapatite (n-HA) was successfully deposited on the PLLA and PLLA/Col nanofibers. We observed that the formation of n-HA on PLLA/Col nanofibers was faster and significantly more uniform than on pure PLLA nanofibers. The n-HA significantly improved the hydrophilicity of PLLA/Col nanofibers. From the results of cell attachment studies, n-HA deposition enhanced the cell capture efficacy at the 20-minute time point for PLLA nanofibers. The E-modulus values for PLLA+n-HA with cells (day 1 and day 4) were significantly higher than for PLLA+n-HA without cells. Based on these observations, we have demonstrated that n-HA deposition on nanofibers is a promising strategy for early cell capture.

By the method of injection molding combined with thermally induced phase separation (TIPS), a novel nerve conduit with a plurality of channels and macro-/microporous architecture was fabricated using poly (lactide-co-glycolide) (PLGA, 75:25; Mn=1.22x10(5)). The diameter of the conduits and the number of channels could be regulated by changing the parameters of the mold, and the porosity of the conduit was as high as 95.4%. Meanwhile, the hierarchical pore architecture of the walls could be controlled through varying the solution concentration and the contents of porogen. The degradation study in vitro showed that 7-channel conduit could hold its apparent geometry for about 12 weeks in phosphate buffer solution (PBS) at 37degreesC, and the pH values of the degradation solution were detected in the range 4.1-4.5. The influences of the conduit architecture on the cell attachment, spreading, and proliferation were evaluated by culturing rat mesenchymal stem cells alone or together with Schwann cells in vitro. The implantation of the PLGA conduit in the spinal cord showed that it had good biocompatibility, and no obvious inflammatory response was detected. Therefore, the results implied that these PLGA multiple-channel nerve conduits have the potential use for spinal cord injury.