TABLE II.

Summary of muscle bioprinting successes.

Article title	Material/s	Successes	Challenges	Reference
3D bioprinted human skeletal muscle constructs for muscle function restoration	PCL, gelatin, fibrinogen, HA, glycerol	Successful implantation of printed construct into rodent model, achieving 82% functional recovery.	Rodent model was immunocompromised, and therefore further study is required into inflammatory and immune responses.	37
Three-dimensional bioprinting of functional skeletal muscle tissue using gelatin methacryloyl- alginate bioinks	GelMA alginate Calcium Peroxide	GelMA gel was capable of cross-linking while maintaining cell viability and muscle tissue formation. Bioink was further improved through the addition of oxygen-generating particles, increasing the metabolic activity of cells.	The addition of oxygen releasing particles in GelMA—alginate bioinks created calcium chloride ions, stimulating cross-linking, and forming a dense gel with cells only capable of surviving one day of culture. Further studies are required into the effects of oxygen releasing particles within the body or in other constructs.	21
Three-dimensionally printed biological machines powered by skeletal muscle		Synthesized functional muscle constructs which responded to electrical stimulation, allowing for directed force generation and motion.	Further study into the integration of vascular networks and nerves is required for the synthesis of larger constructs and in vivo implantation.	143
3D cell printing of functional skeletal muscle constructs using skeletal muscle-derived bioink	Skeletal muscle dECM PCL	Successfully decellularized and printed constructs from skeletal muscle-derived ECM bioink. The resulting construct retained receptors and adhesion factors.	Requires living tissue to begin with, cannot yet be synthesized ex vivo.	39
Neural cell integration into 3D bioprinted skeletal muscle constructs accelerates restoration of muscle function	PCL, gelatin, fibrinogen, HA, glycerol	Integration of nerve cells into bioprinted muscle construct improved cellular differentiation and long-term survival as well as facilitated the formation of neuromuscular junctions.	Study was performed in an immunocompromised rodent model; therefore, more study is required into immunological effects.	38
Biohybrid robot with skeletal muscle tissue covered with a collagen structure for moving in air		Successful development of collagen encapsulated skeletal muscle construct, termed as a “biohybrid robot” capable of motion and object manipulation.	Construct was small in scale, negating the requirement for adequate vascularization.	144