# Carbon Nanoparticles and Their Biomedical Applications
## 12 Scaffolds, Tissue Engineering, and Healing
Induction of the cell and differentiation and tissue formation (nervous tissue and myocardium) (parts of the figure were drawn using pictures from Servier Medical Art. Servier, licensed under a Creative Commons Attribution 3.0 Unported License.). also confirmed the osteogenic potential of CNP. They used a 3D scaffold made of graphene functionalized with calcium phosphate, which induced osteogenic differentiation in vitro in human mesenchymal stem cells and bone regeneration in vivo in a mouse calvarial defect model [135]. [PERSON] et al. also confirmed the therapeutic potential of CNP materials. They coated a titanium alloy implant with graphene and used it in the treatment of femoral condyle defects in rabbits. The nanomaterial promoted and accelerated osteogenesis and osseointegration. The quality of newly formed bone, bone mineralization, and implant attachment was better in the graphene group than in the non-graphene group [136]. CNPs can help to promote the regeneration of other types of tissue, including sensory, cardiac, and vascular tissue. Retinal damage often leads to an irreversible loss of sight. To regenerate this important tissue is crucial to protect vision. Carbon nanotubes and nanofibers were used by [PERSON] et al. to promote the differentiation of human embryonic stem cells into photoreceptor precursor cells. In clinical practice, this could be applied to the treatment of damaged retinas [137]. The incidence of cardiovascular disease continues to rise. Ischemic heart diseases irreversibly damage the myocardium, which has a very limited regenerative capacity and loses its function. In the most severe cases, the only treatment is a heart transplant, but there is a severe shortage of organs. A therapeutic option could be to induce regeneration of the heart muscle and blood vessels or even to create a new functional organ. Scaffolds or injectable hydrogels with CNPs alone or seeded with stem cells might help to induce the regeneration of damaged tissue. They must mimic the extracellular matrix, which provides mechanical support as well as crucial signals required for stem cell maturation and differentiation. They have good biocompatibility, mechanical properties, and electrical conductivity that cardiac cells need to form new functional tissue. The scaffold of PEG with GO cultured with neonatal rat ventricular myocytes facilitated the growth of cardiac cells, their conductivity, and contractility more than PEG [138]. [PERSON] et al. fabricated a biodegradable chitosan scaffold with GO-gold nanosheets. They implanted and tested its properties both in vitro in an isolated heart and in vivo in a rat model of myocardial infarction. After 5 weeks, the ECG results showed that the scaffold improved the conduction velocity and the cardiac contraction in the infarcted cardiac tissue. ECHO proved that the implant increased the ejection fraction. These positive effects were not associated with immune system activation and inflammation [139]. The delivery of stem cells to scaffolds with CNPs can promote neoangiogenesis and, thus, restore blood flow in the damaged area [90]. [PERSON] et al. confirmed that different concentrations of GO and reduced GO promote angiogenesis [140]. Neoangiogenesis is also crucial for the regeneration of peripheral nerves. [PERSON] et al. fabricated a polycaprolactone scaffold with GO that supported not only Schwann cells and neurite growth but also angiogenesis, which is necessary for nerve regeneration. The presence of GO enhances the activity of the AKT-eNOS-VEGF axis [141]. We cannot omit the involvement of CNPs in the healing of skin wounds, including chronic and infected wounds. MWCNTs can control infection and accelerate the regenerative processes (fibroblast proliferation, re-epithelialization) even in difficult-to-treat diabetic wounds and burns [142]. [PERSON] et al. described the effect of bacterial cellulose with MWCNTs, which induced faster closure of diabetic wounds, re-epithelialization, and the formation of healthy granulation tissue.