Characterization of photocrosslinked alginate hydrogels for nucleus pulposus cell encapsulation

Intervertebral disc (IVD) degeneration is a significant health concern in the USA. Tissue engineering strategies have the potential to provide a viable alternative to current treatments. Nevertheless, such approaches require a suitable biomaterial scaffold for IVD tissue regeneration. Calcium crosslinked alginate has traditionally been used for in vitro culture of nucleus pulposus (NP) cells of the IVD. However, such ionically crosslinked hydrogels lose structural integrity over time. Recently, various polymers have been modified with photopolymerizable functional groups to create covalently crosslinked hydrogels. This technology may be employed to maintain the structural and mechanical integrity of three-dimensional alginate hydrogels. In this study, photocrosslinkable alginate was synthesized and evaluated for material properties and the ability to maintain the viability of encapsulated NP cells. Photocrosslinked alginate at varying percent modifications and weight/volume percentages displayed equilibrium swelling ratios and Young's moduli of 30.52 +/- 1.782 to 43.50 +/- 1.345 and 0.5850 +/- 0.1701 to 8.824 +/- 0.6014 kPa, respectively. The viability of encapsulated NP cells was highest in hydrogels at lower percent modifications, and decreased with time in culture. Taken together, this study is the first to demonstrate that photocrosslinked alginate can be used for cellular encapsulation and synthesized with tunable material properties that may be tailored for specific applications.