Soft Biomaterial Study for 3-D Tissue Scaffold Printing

In 3-D scaffold printing, it is critical to find a material that is suitable for your printing method, printing speed, and ease of use. For a biomaterial to best suit solid freeform fabrication techniques, 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. Ionic crosslinkable, photocrosslinkable, and thermo-sensitive hydrogels have all been investigated and found to not fully satisfy our every requirement for SFF printing. Ionic crosslinking hydrogels can gel rapidly but tend to involve additional steps for crosslinking like freeze drying, stirring, and shaking, while some form beads, not homogenous gels. Some photocrosslinkable hydrogels would not work due to the concern for viability of cells in initial gel layers receiving copious amount of UV light. Thermosensitive hydrogels meet most of the requirements except that they are reversible gels. A new type of gel that obtains the qualities of a photocrosslinkable and thermosensitive hydrogel satisfies every requirement. A PEG-PLGA-PEG thermosensitive triblock copolymer additionally crosslinked with photocrosslinkable Irgacure 2959 allows for quick transition from solution to gel with a post-processing step utilizing UV light would add additional crosslinks to the gel structure resulting in an irreversible hydrogel.