Cell-laden alginate dialdehyde-gelatin hydrogels formed in 3D printed sacrificial gel

Alginate dialdehyde-gelatin (ADA-GEL) hydrogels have been reported to be suitable matrices for cell encapsulation. In general, application of ADA-GEL as bioink has been limited to planar structures due to its low viscosity. In this work, ring shaped constructs of ADA-GEL hydrogel were fabricated by casting the hydrogel into sacrificial molds which were 3D printed from 9% methylcellulose and 5% gelatin. Dissolution of the supporting structure was observed during the 1^st week of sample incubation. In addition, the effect of different crosslinkers (Ba²⁺ and Ca²⁺) on the physicochemical properties of ADA-GEL and on the behavior of encapsulated MG-63 cells was investigated. It was found that Ba²⁺ crosslinked network had more than twice higher storage modulus, and mass decrease to 70% during incubation compared to 42% in case of hydrogels crosslinked with Ca²⁺. In addition, faster increase in cell viability during incubation and earlier cell network formation were observed after Ba²⁺ crosslinking. No negative effects on cell activity due to the use of sacrificial materials were observed. The approach presented here could be further developed for cell-laden ADA-GEL bioink printing into complex 3D structures.