Thermosensitive/Photocrosslinkable Hydrogel for Soft Tissue Scaffold Printing

A new type of hydrogel for solid free-form fabrication (SFF) and rapid prototyping (RP) that obtains the qualities of a photocrosslinkable and thermosensitive hydrogel would benefit the tissue engineering field. For a material to best suit SFF and RP, it must: 1) be a low-viscous solution before being printed, 2) involve easily joined on-substrate mixing to form a homogenous gel, 3) have a short solution to gel transition time, 4) be a mechanically strong gel, and 5) have an irreversible gelation processes. A biodegradable, biocompatable thermosensitive triblock copolymer, poly(ethylene glycol-b-(DLlactic acid-co-glycolic acid)-b-ethylene glycol) (PEG-PLGA-PEG), crosslinked with photocrosslinkable Irgacure 2959 allows for quick irreversible transition from solution to gel with a post-processing step utilizing UV light. A material that gels instantaneously from a non-viscous solution to a 3-dimensional building gel could be used in multiple different types of SFF methods already developed. Since the material is also biocompatible, it can be used to replicate many different types of tissues. In this paper, the mechanism of gelation is proposed and the material relationship to the initial viscosity is investigated.