## 8 Relevant Applications of Melt Electrospinning
### Biomedical Applications and Tissue Engineering
[234] produced scaffolds via melt electrowriting to emulate the biomechanical behavior of tendons and ligaments. The material used was a copolymer of PCL and acryloyl carbonate p(CL-\(co\)-AC) to manufacture aligned, crimpled, and mechanically robust elastomeric scaffolds. These were proven to be cytocompatible after performing a test with murine cells. Cell adhesion was also demonstrated with human mesenchymal stem cells (hMSC). Thus, these constructs entail a promising approximation in tendon and ligament tissue engineering. One of the most recent works concerning melt electrowritten fibers applied in tissue engineering was carried out by [PERSON] et al. [235]. The aim was to study the cell organization based on the fiber arrangement, which is crucial in orthopedic applications in ligament tissue engineering as a high degree of cell alignment is found in the native tissues. Therefore, three different patterns of porous PCL scaffolds were tested (aligned, crimped, and random). The aligned-fibrous scaffold was the only one that permitted cells to orientate towards the fiber main direction. Furthermore, for the development of a functional scaffold with an application in the anterior cruciate ligament and an eventual bone-ligament-bone construct, this scaffold was combined with a melt electrospun compartment that was seeded with osteogenesisly induced hMSC. Experimental results showed that fiber organization is capable of inducing cell alignment and that cell-seeded bone-ligament-bone structures have increased mechanical resilience and elasticity even though the mechanical properties were lower than those of native tissue. Cardiac tissue engineering is another relevant application of melt electrospinning. Like other tissues, the heart presents a low healing response after a cardiac injury and is usually associated with a high mortality rate [236]. Attempts have been made to regenerate the tissue with biomaterials, but the current techniques present a main drawback:  
Figure 14: Scaffold implantation and cell therapy as approach for repair of tendon injuries. **(a)** The hierarchical architecture of tendon: Collagen triple-helices self-assemble into fibrils. Bundles of fibrils form fibers, which constitute tendon fascicle. Tendon fibroblasts (tenocytes) reside between collagen fibers. Fascicles are wrapped by endotenon, a layer of connective tissue containing blood vessels, nerves and lymphatics. Multiple fascicles are further surrounded by another connective tissue layer, epitenon, to form the tendon tissue [232]. Extracellular matrix (ECM) of cartilage: Three classes of proteins exist in articular cartilage: collagens (mostly type II collagen); proteoglycans (primarily agrecan); and other noncollagenous proteins (including link protein, fibronectin, cartilage oligomeric matrix protein) and the smaller proteoglycans (biglycan, decorin and fibromyalgia). The interaction between highly negatively charged cartilage proteoglycans and type II collagen fibrils is responsible for the compressive and tensile strength of the tissue, which resists load in vivo. Abbreviation: COMP, cartilage oligomeric matrix protein [230]. **(b)** Biofabricated soft network composites for cartilage tissue engineering: melt electrospinning writing (MEW) allows the design and fabrication of medical grade PCL fibrous networks. A soft matrix of hydrogel to emulate the proteoglycan matrix of articular cartilage was loaded into fibrous networks [231]. Based on [232; 233; 230]. the impossibility to manufacture fiber-organized structures and mimic the mechanical environment of native cardiac tissue. This issue can be overcome by melt electrospinningnims as it allows a scaffold fabrication with aligned fibers. [PERSON] et al. [54] prepared a blend of poly (hydroxymethyllylylycolide-co-\(\varepsilon\)-caprolactone) (pHMGCL), a copolymer that presents higher hydrophilicity compared to PCL, and PCL (pHMGCL/PCL) via melt electrospinningnims. Additionally, its degradability rate could be tuned, and the fibers could be further functionalized.