**5.3 3D bioprinting**

3D Bioprinting is a rapid prototyping and additive manufacturing technique used to produce artificial implants. Tissue and organ regeneration is one of the fields where 3D bioprinting is used. Bioprinting is layer-by-layer depositing of biological material with living cells using computer-aided transfer processes. Although whole vascularized organs for transplantation have not been produced by bioprinting yet, generation of the scaffold-free tubular trachea [29] and generation of scaffold-free nerve constructs using human gingiva-derived mesenchymal stem cell spheroids were reported [30]. 3-D bioprinting has been used in the production and transplantation of several organs including tracheal splints, vascular grafts, cartilaginous structures, heart tissue, multi-layered skin, and bone. The final goal is industrial bioproduction of individualized functional 3D organs for clinical application.

Nanotechnology has been useful for localized, sustained, and controlled delivery of drugs including immunosuppressive agents and clinically relevant biomarkers. Nano particles can also be used to deliver contrast agents to assist in delineating anatomy and therefore nanotechnology contributes to imaging of clinically relevant biomarkers and functional parameters for diagnosis and treatment [31].

Gene therapy has the potential to eliminate problems associated with immunosuppression by allowing the production of immunomodulatory proteins in the donor grafts resulting in local immunosuppression. Gene therapy may also prevent chronic rejection [32].
