# Electrospun Nanofibrous Membranes for Tissue Engineering and Cell Growth
## 6 Pla  
PLA is a biodegradable polyester which is produced from renewable resources and used in many applications; from biomedicine to 3D printing. PLA is rarely electrospun solely [95], but mostly in combination with diverse blend partners. For example, [PERSON] et al. used an alginate/PLA blend for emulsion electrospinning [96]. After making the sodium alginate water-insoluble by ion exchange of Na\({}^{+}\) in a CaCl\({}_{2}\) solution, these nanofiber mats showed significantly increased mechanical properties, as compared to pure PLA, as well as significantly enhanced hydrophilicity. The latter point was reflected by significantly increased cell proliferation and cell differentiation on alginate/PLA nanofiber mats, which was also supported by structures in the nanofiber mats similar to the ECM, including a rougher fiber surface than in pure PLA fibers. Similar results were obtained by [PERSON] et al., working with periodontal ligament cells and bone marrow stromal cells [97]. Carbonated calcium deficient hydroxyapatite (CDHA) was blended with PLA by [PERSON] et al. [98]. They used chloroform and dimethylformamide (DMF) as solvent for the electrospinning process. The PLA/CDHA nanofiber mats degraded faster than pure PLA fibers and allowed for more uniform apatite coating, besides buffering the pH decrease that usually occurs during PLA degradation. Furthermore, they showed improved bioactivity and biocompatibility, as compared to pure PLA nanofiber mats. The improved cell attachment and proliferation was attributed to the CDHA forming a similar crystalline structure, as in deproteinated bone apatite. To combine the mechanical properties of PLA with cell recognition properties of some biopolymers, [PERSON] et al. blended PLA with fibrinogen [99]. Seeding human umbilical endothelial cells on the received nanofiber mats, they found good adhesion and reduced cell movement in randomly oriented nanofiber, but elongated cell shape and significantly increased cell mobility on aligned nanofibers. They verified this finding by testing the artificial wound coverage, which was found to be superior for the aligned samples, while directional migration was almost not visible on the random nanofiber mats. On the other hand, randomly spun nanofiber mats were suggested for endothelial of implants, as opposed to directed nanofibers, which could be used for guided neovascularization. Here, fiber orientation was clearly the reason for the different growth of the cells, since the residual parameters were kept constant. Another approach was chosen by [PERSON] et al., who used maleic anhydride grafted PLA as a matrix with incorporated cellulose nanocrystals (CNCs) [100]. They found decreased nanofiber diameters with increasing CNC content, improved thermal and mechanical stability, as well as higher stability during in vitro degradation. Additionally, by seeding human adult adipose derived mesenchymal stem cells, the nanofiber mats were found to be nontoxic and to support cell proliferation. A multi-blend of PLA, human-like collagen (HLC), chitosan, and PEO in different ratios and spun through two needles, was investigated by [PERSON] et al. [101]. They found that the blended fibers had a smaller diameter than pure PLA and a larger one than HLC/chitosan/PEO alone. Depending on the amount of HLC, chitosan, and PEO, they found varying hemocompatibility and better biocompatibility than for pure PLA, which was suggested to result from the interaction between chitosan and blood cells. An approach without biopolymers was reported by [PERSON] et al., who spun PLA/PCL bilayer nanofiber tubes with an inner PCL layer between outer PLA layers and used 3T3 mouse fibroblasts, as well as human venous myofiblists, to test cell attachment, proliferation, and migration [102]. This scaffold was shown to allow for attachment, spreading, and growth of mouse fibroblasts and human myofiblists.