Functionalizing bioinks for 3D bioprinting applications.

3D bioprinting has emerged as the intersection between chemistry, biology and technology. Through its integration of cells, biocompatible materials and robotic-controlled dispensing systems, the process enables the production of structures that are biomimetic and functional, thus revolutionizing the concept of tissue engineering. One of the biggest limitations of 3D bioprinting for tissue engineering is the lack of printable materials (bioinks) with all-inclusive properties desirable for the construction of engineered 'bio-physico-functional' tissues and organs. Thus, bioinks are required to be functionalized or altered to produce the most desirable bioarchetypes. Functionalization methods vary across chemical, mechanical, physical and biological methods, and common methods include blending of materials, coatings, crosslinking and exploiting functional groups. In this short review, a description and critical comparison of reported functionalization methods, focusing on their effects and contributions toward bioinks, have been presented.