Fig. 2

Nanomaterials and nanostructures for engineering skeletal muscle tissues and improving muscle regeneration. A. 3D Anisotropic cryogels composed of conductive aligned polydopamine coated carbon nanotubes (PCNTs) for muscle regeneration. (i) Schematic of the fabrication of PCNT cryogel [90]. (ii) Compressive, conductive and highly aligned skeletal muscle PCNT cryogel mimicking mechanical properties of natural muscle and inducing cell alignment and differentiation. (iii) Evaluation of in vivo muscle regeneration in a rat TA muscle defect model after implantation of the PCNT cryogel for 4 weeks. Red arrows indicate the presence of freshly created blood vessels, while black arrows indicate the newly formed muscle fibers assessed by centronucleated myofibers. B. Anti-inflammatory cytokine immobilized AuNPs for improving muscle function in dystrophic mice. (i) Schematic showing PEGylation and interleukin-4 (IL-4) conjugations to AuNPs for T cell recruitment and muscle function improvement. (ii) Enhancement of muscle functions observed in mdx mice by IL 4-conjugated AuNPs. Scale bar: 300 μm [105]. C. Stretchable nanofibrous sheet using coaxial electrospinning for improving muscle regeneration. (i) Schematic showing co-axial electrospinning of PCL and gelatin solutions, followed by chemical crosslinking of the gelatin core using glutaraldehyde. The sacrificial PCL layers were removed to produce gelatin co-axial nanofibers (NF). (ii) NF5 + C2C12 (5% stretched nanofiber with cell) showed the largest muscle regeneration compared to NF0 + cell (unstretched nanofiber with cell) or NF0 (unstretched nanofiber) (n: interface between host tissue and implants. o: host muscle tissue) [111]. (iii) Stretchable nanofiber for enhancing myotube formation. D. Nanostructured fibers resembling the ordered and striated pattern of myofibrils via self-assembly of ABA triblock copolymers.. (i) Schematic showing the fiber fabrication process and structural characteristics of the fiber. (ii) Nanostructured fiber mimicking the patterns (A and I band) and the size of myofibril. (iii) Images showing elongation ratios ranging from one to five. As the elongation ratio increased, the diameters of the subsequently treated fibers rapidly decreased [112]