Evaluation of sustained-release in-situ injectable gels, containing naproxen sodium, using in vitro, in silico and in vivo analysis.

The study aimed to fabricate naproxen sodium loaded in-situ gels of sodium alginate. Different in-situ gel forming solutions of naproxen sodium and sodium alginate were prepared and gel formation was studied in different physiological ions i.e., CaCl2 and Ca-gluconate. The prepared gel formulations were evaluated for different physical attributes such as gelation time, sol-gel fraction, ATR-FTIR spectroscopy and in silico molecular dynamics (MD) simulations. Drug release studies were carried out in a dialysis membrane using USP dissolution basket apparatus-I. In vivo anti-inflammatory studies were performed in Sprague-Dawley rats having carrageenan-induced hind paw inflammation. Higher polymer concentration in formulations resulted in decreased gelation time and an increased gel fraction. The ATR-FTIR and MD simulation revealed H-bonding between the alginate and naproxen sodium at 3500-3200 cm-1 with a RMSD of ∼2.8 Å and binding free energy ΔGpred (GB) = -10.93 kcal/mol. In vitro drug release studies from F8CAG suggested a sustained release of naproxen sodium. In vivo studies revealed a continuous decrease in swelling degree (≈-5.28 ± 0.210 mm) in inflamed hind paw of Sprague-Dawley rats over 96 h. The in-situ gel forming injectable preparation (F8CAG) offers a sustained release of naproxen sodium in the articular cavity which promises the treatment of chronic inflammatory conditions such as arthritis.