Characterization and restoration of degenerated IVD function with an injectable, in situ gelling alginate hydrogel: An in vitro and ex vivo study

Abstract

Intervertebral disc (IVD) degeneration is a naturally, irreparable process that causes loss in IVD hydration, cellularity, and, mechanical stability. Invasive surgical attempts to ease back pain and, radiculopathy have shown to cause increased degeneration along the rest, of the spine. Due to its highly tunable mechanical and degradation, properties, alginate is a viable option for a less-invasive injectable, repair for IVD degeneration. This study centers on the characterization, of in situ gelling alginate and subsequent injection into enzymatically, degraded motion segments., In situ gelation of 2% alginate (% w/v PBS) was performed using calcium, carbonate (CaCO3) and glucono-δ-lactone (GDL) and compared to, instantaneously gelled 2% alginate crosslinked with calcium chloride., After characterization of multiple molar concentrations, a ratio of, 60mM:120mM CaCO3:GDL was determined to have the most optimum properties, for injection. Enzymatically degraded bovine caudal motion segments were, injected with the optimized in situ gelling alginate and mechanically, loaded; injected motion segments were compared to intact specimens, degraded specimens, and specimens injected with 20% gelatin to, corroborate with previous ex vivo injection studies., Overall, injection of in situ curing 2% alginate into an enzymatically, and mechanically degraded IVD restores function via reduction of height, loss over long-term cyclic loading, is constrained within the disc with, no injection site leakage, and successfully fills all void spaces created, by chemonucleolysis with 1% collagenase-f. These findings, along with the, ability of alginate to be specifically tailored to support cell, viability, show promise for a tissue engineered injectable NP substitute for the reversal of disc degeneration.