Tissue Engineering Tissue engineering and regenerative medicine have emerged as a potential strategy in improving the health and diagnostics of patients. The ultimate goal of tissue engineering is to design and fabricate the damaged human tissue into a functional human tissue suitable for regeneration, replacement or repair of the damaged structures. Scaffolds of natural and synthetic polymers, metals and ceramic has been used to reconstruct the damaged tissues. However, these scaffolds could not find success in regenerating all human structures. Later, bio fabrication method has been introduced to enhance regeneration process of damaged human tissue. 3D bio printing Addictive manufacturing or 3D bioprinting has emerged as potential scaffold free fabrication methods for damaged human structures. This is considered as most promising and futuristic bio fabrication method for tissue engineering application. This document provides an understanding on parameter and properties involved in the development of bio ink for spheroid and organ printing. This selection of bio-ink depends on the process of bioprinting. The bioprinting process are of different types such as stereolithography, inkjet 3D printing, extrusion, laser-assisted printing, selective laser melting and Poly-Jet printing. Thus, based on the feasibility and easy accessibility of the bioprinter, extrusion-based printing process was selected our project. The basic requirements for the selection of successful inks based on polymer or polymer blends, and composites are described. The most commonly explored natural materials for 3D printing are alginate, HA, collagen and chitosan. However, synthetic polymers can be easily modified to meet specific requirements by optimizing mechanical and physicochemical properties, pH and temperature responses. This fabrication method involves development of printable solutions so called bio-inks. Incorporation of cells into the bio-inks and incubation in a bio reactor for patient specific functional tissues for regeneration, repair and replacement of damaged tissue. Spheroid printing The cell-material interactions using conventional cell culture practices has led to numerous understandings on cellular formation, function and impact of synthetic or natural biomaterial in achieving the cellular properties. Also, cellular interaction and regeneration process of the damaged tissue. However, in-vitro models as 2D models, which does not provide the replication of all the mechanical and biochemical signals cues of the tissues or organs. This is reason researcher started developed 3D cell culture with the help of bio 3D printing technology. Spheroid formation is the self-assembly of cells in the absence of a scaffold or ECM that mimics the natural process of that occur during embryogenesis, morphogenesis and organogenesis. Spheroid mimics the architectural and functional characteristics of native tissue in in-vitro. One of the emerged methods for the preparation of spheroid formation is using microfluidics techniques. Spheroids can be used as a model system to study the molecular events controlling self-assembly of multi cellular tissues. Development of tumor spheroids helps in understanding the molecular mechanisms behind the cancer and it can used as a tool to study the efficacy of the drug developed against these cancers. Thus, Spheroid printing helps to develop alternative testing methods for animal models for cancer drug research and personal therapeutic applications.
