Inkjet printing and cell seeding thermoreversible photocurable gel structures

We have developed a biocompatible fluid suitable for inkjet delivery that gels by a tandem mechanism of a rapid physical gelation followed by a photoactivated chemical cross-linking. We prepared 20 vol% aqueous solutions of acrylate functionalised Pluronic F127, a poly(ethylene glycol-b-propylene glycol-b-ethylene glycol) (PEO–PPO), with triethanolamine and eosin Y as a photocurable cross-linker combination; poly(ethylene glycol) diacrylate was also added to the solution to improve the sol–gel transition. This fluid has a viscosity <20 mPa s at 5 °C and is suitable for inkjet printing. We used a piezoelectric drop-on-demand inkjet printer at this temperature to print single and multilayer structures on a substrate held at room temperature. The dimensions of the resulting structures are consistent with models developed for the interaction of overlapping drops. After photocrosslinking the resulting gel structures, which are stable in an aqueous environment, were successfully seeded with fibroblast cells also delivered by an inkjet printer.