## 8 Relevant Applications of Melt Electrospinning
### Biomedical Applications and Tissue Engineering
[215], melt electrospun PCL tubular scaffolds were proved to be noncytotoxic and to support cell growth of three different types of cells: primary human osteoblasts (hOB), primary mouse osteoblasts (mOB), and human mesothelial cells. The low melting temperature, long degradation kinetics of PCL and its capability to be blended with other polymers has made it a good material for tissue engineering applications. Furthermore, to mimic the bone microenvironment, the scaffolds can easily be coated with a layer of calcium phosphate (CaP). Scaffolds seeded with human cells presented a >90% cell viability and those seeded with mOBs showed the formation of a mineralized matrix after 4 weeks of culture on the scaffold fibers and inside and across the pores [215]. Further investigations by [PERSON] et al. [212] led to the manufacturing of PCL scaffolds with an average fiber diameter of 15 \(\upmu\)m and an average pore size of 250-300 \(\upmu\)m, which were again coated with a CaP layer. In vitro ovine osteoblasts proliferation on such scaffolds was studied. Results showed a cell viability above 90% after 20 and 40 days of culture, a completely covered scaffold surface after 40 days, and the secretion of ECM. Recent studies seem to demonstrate that thicker fiber diameters (i.e., in the range of a few micrometres) have an increased proliferative potential compared to nanofibers. However, smaller-sized fibers promote a better cell adhesion due to the high surface area that nanomaterials possess [216, 217, 218]. In between, [PERSON] et al. [219] prepared fiber mats in another application for bone tissue regeneration using PLA. This polymer has been extensively been applied in many biomedical applications because it is biocompatible, biodegradable and renewable [220]. Furthermore, it presents a mild foreign reaction [221] without inflammatory reaction [222]. Compared to the performance of the same experiment with a solution-electrospun fiber mat, melt electrospun fibers showed better results in cell viability and differentiation. [PERSON] et al. [200] took a step forward and carried out an in vivo study, proving that it is possible to regenerate rabbit calvaried defects using hybrid nanofiber scaffolds of silk fibroin (SF) and poly(glycolic acid) (PGA). Silk fibroin is a natural biopolymer with excellent biomedical and mechanical properties, including tensile strength, biocompatibility, hydrophilicity and biodegradability, which makes it a good candidate for bone tissue engineering applications [223]. It can also be combined with other materials to modify certain properties. In this case, PGA was chosen mainly for its biodegradability and thermoplastic properties, which enhance cell proliferation. The scaffolds were inserted in rabbit damaged crania and the analysis performed after 4 and 8 weeks revealed that SF-PGA hybrid scaffolds had indeed promoted bone tissue regeneration [200]. Another application including bone tissue engineering is the periodontal tissue regeneration. Two relevant studies included in vivo experiments. First, [PERSON] et al. [224] synthesized a PCL composite with \(\beta\)-tricalcium phosphate that was later coated with CaP. The scaffold was then seeded with osteoblasts and cultured in vitro for 6 weeks before being complemented with periodontal ligament cell sheets, attached to a dentine block and implanted into athymic rats. Results confirmed that the tissue was integrated between the bone and the periodontal ligament compartments as there were high levels of vascularization and a tissue with a structure similar to that of native periodontal tissues was formed. The second study was performed by [PERSON] et al. [225] using highly porous PCL scaffolds that were seeded with cells from three different sources: gingival cells (GCs), bone marrow-derived mesenchymal stromal cells (Bm-MSCs), and periodontal ligament cells (PDLCs). After the healing process of a periodontal ovine model for 5-10 weeks, the implants with Bm-MSCs and PDLCs showed much better results, indicating that periodontal regeneration was feasible.