# Carbon Nanoparticles and Their Biomedical Applications
## 12 Scaffolds, Tissue Engineering, and Healing  
CNPs exhibit excellent biocompatibility and can be easily functionalized to enhance the viability of specific cell types and control their behavior (shape, adhesion, proliferation, differentiation, and dedifferentiation toward multipotency). Therefore, CNPs can serve as material for coating scaffolds (3D scaffolds enable the formation of tissue from stem cells). The results of the following studies suggest that CNPs have great potential for use in regenerative medicine. Studies especially show their regenerative effects on the nervous system, bones, and cartilage (Figure 5) [123; 124]. Graphene has been proven to support the growth of mouse hippocampal neurons, enhance the number of neurites and their lengths, and modulate synaptogenesis as well as neural activity [125; 126]. Importantly, graphene, GO, and carbon nanotubes can induce the differentiation of mouse embryonic stem cells into dopaminergic neurons, which decline in patients with Parkinson's disease [127]. The implantation of an electrospun microfiber scaffold coated with self-assembled colloidal graphene into the striatum or subventricular zone of adult rats has led to the suppression of microglial and astrocyte activation, inhibiting inflammation, and significantly reducing glial scarring in the brain after a brain injury [128]. The 3D porous scaffold is an excellent microenvironment for the growth, activity, and proliferation of neurons to form neuronal tissue. It mimics the in vivo situation during neural development [128]. Hippocampal neurons cultured on a 3D graphene scaffold show more extensive connectivity and a higher degree of synchronicity than neurons cultured on a 2D scaffold. Moreover, the two regimes of synchronicity were detected as highly synchronized and moderately synchronized. The first have never been detected in 2D scaffolds [129]. [PERSON] et al. implanted a 3D scaffold with GO for 30 days into the injured spinal cords of rats. It potentiated the healing process and promoted angiogenesis around and within the scaffold structure. New functional blood vessels and neural axons were found in the damaged tissue [130]. CNPs not only help to regenerate the central nervous system but also the peripheral. [PERSON] et al. created an electrospun composite scaffold of graphene and silk fibroin that promotes Schwann cell growth and could be used in the treatment of peripheral nervous system injuries [131]. Similar results were described by [PERSON] et al., who cultured Schwann cells with a scaffold fabricated from polycaprolactone and CNT modified with brain-derived neurotrophic factors that promote cell proliferation and myelin production. The in vivo part of this study proved the regenerative properties of the scaffold. The rat sciatic nerve defect model improved the functional recovery of the damaged sciatic nerve [132]. Nanoparticles can also promote bone, cartilage, skin, and muscle formation and regeneration [133]. Bone injuries, fractures, and bone-affecting diseases are often associated with poor healing and the necessity of the use of bone grafts. A major problem is the limited availability of tissues; the solution would be tissue engineering [133]. In vitro, graphene potentiates the differentiation of stem cells into osteoblasts and enhances osteogenesis. In vivo studies showed that CNPs potentiate the repair of bone defects and ectopic bone formation [134]. [PERSON] et al. prepared a 3D porous nanohydroxyapatite scaffold with GOs and found that (in vivo, in a rabbit model) a circular calvarial defect (4 mm in diameter) was fully healed by this scaffold. They performed CT imaging and analyzed bone tissue samples. The scaffold improved osteogenesis, cell proliferation, and collagen deposition compared to rabbits treated with standard therapy [134]. The results of [PERSON] et al. Figure 5: Regenerative potential of CNPs. Stem cell cultivation with graphene.