Injectable, self-healing hydrogels based on gelatin, quaternized chitosan, and laponite as localized celecoxib delivery system for nucleus pulpous repair

Utilization of injectable hydrogels stands as a paradigm of minimally invasive intervention in the context of intervertebral disc degeneration treatment. Restoration of nucleus pulposus (NP) function exerts a profound influence in alleviating back pain. This study introduces an innovative class of injectable shear-thinning hydrogels, founded on quaternized chitosan (QCS), gelatin (GEL), and laponite (LAP) with the capacity for sustained release of the anti-inflammatory drug, celecoxib (CLX). First, synthesis of Magnesium-Aluminum-Layered double hydroxide (LDH) was achieved through a co-precipitation methodology, as a carrier for celecoxib and a source of Mg ions. Intercalation of celecoxib within LDH layers (LDH-CLX) was verified through a battery of analytical techniques, including FTIR, XRD, SEM, EDAX, TGA and UV-visible spectroscopy confirmed a drug loading efficiency of 39.22 ± 0.09 % within LDH. Then, LDH-CLX was loaded in the optimal GEL-QCS-LAP hydrogel under physiological conditions. Release behavior (15 days profile), mechanical properties, swelling ratio, and degradation rate of the resulting composite were evaluated. A G* of 15-47 kPa was recorded for the hydrogel at 22-40 °C, indicating gel stability in this temperature range. Self-healing properties and injectability of the composite were proved by rheological measurements. Also, ex vivo injection into intervertebral disc of sheep, evidenced in situ forming and NP cavity filling behavior of the hydrogel. Support of GEL-QCS-LAP/LDH-CLX (containing mg2+ ions) for viability and proliferation (from ~94 % on day 1 to ~134 % on day 7) of NP cells proved using MTT assay, DAPI and Live/Dead assays. The hydrogel could significantly upregulate secretion of glycosaminoglycan (GAG, from 4.68 ± 0.1 to 27.54 ± 1.0 μg/ml), when LHD-CLX3% was loaded. We conclude that presence of mg2+ ion and celecoxib in the hydrogel can lead to creation of a suitable environment that encourages GAG secretion. In conclusion, the formulated hydrogel holds promise as a minimally invasive candidate for degenerative disc repair.