**5. Conclusion**

Bioprinting has been used to create a variety of complex tissues and has demonstrated great potential as an alternative to autologous, allogeneic and xenogeneic organ and tissue transplantation. Progress towards a complete implantable organ is at various stages of development depending on the organ or tissue to be fabricated.

Some of the greatest developments have been with neural and skin tissues. It has been shown that neuronal cells can be printed without affecting their function or phenotype. In one investigation using an inkjet printer, the printed neuronal cells demonstrated faster and longer neurite growth in comparison to non-printed cells [37]. When implanted, bioprinted neural scaffolds have been able to restore nerve function [38–40].

Complex structures such as skin have been fabricated that include both dermal and an epidermal layers. By using bioprinting technology, it is possible to create a skin model with pigmentation [16]. Bioprinted skin scaffolds have been successfully applied via direct *in situ* printing [48]. Used to repair full thickness wounds in mice, *in situ* bioprinted scaffolds have regenerated skin tissue with a histologically similar appearance to native skin.

A potential use for bioprinted tissues could be in modeling diseased tissues. Research has already been conducted studying the metastasis of bone cancer in a bioprinted bone tissue model [63]. Using bioprinted tissue models it could be possible to gain a greater understanding of the interactions between infected and diseased cells with healthy tissues. By doing so, new treatments can be produced and tested to determine the most effective solution.

Each bioprinting technique has demonstrated the potential to generate fully functional organs, which in the future can be used for applications such as: direct implantation, to fill the gap for much needed donor organs; provide a model system for pharmaceutical testing, and replace the necessity for animal testing; or be used for disease modeling and enable different treatments to be easily explored. Overall, bioprinting is gaining substantial interest in the field of tissue engineering and regenerative medicine due to its capability to produce complex organs and tissues.
