Unravelling the role of hemp straw derived cellulose in CMC/PVA hydrogel for sustained release of fluoroquinolone antibiotic

Abstract

Cellulose fibres derived from hemp stalks, a prevalent biowaste in Northern India, were effectively converted into carboxymethyl cellulose (HS-CMC). Novel environmentally benign hydrogels were synthesized from HS-CMC and polyvinyl alcohol (PVA) using citric acid, a green crosslinker employing freeze-drying method. The HS-CMC/PVA hydrogels were successfully used for sustained release of fluoroquinolone antibiotic, norfloxacin. The hydrogels were characterized using FTIR, XRD, FE-SEM, EDS and thermal stability and evaluated for their carbonyl content, swelling ratio, in-vitro drug release behaviour and bactericidal properties. Successful isolation of cellulose from hemp stalks and its conversion into hydrogel with the presence of ester and carbonyl linkages was confirmed by FTIR. Thermal stability was impaired when cellulose fibres were converted into HS-CMC via carboxymethylation, as the crystalline structure was utterly disrupted. For the hydrogel, the equilibrium swelling ratios at pH -1.2 and 7.4 were assessed as 378.4 % and 538.7 %, respectively, higher than reported CMC hydrogels. The norfloxacin (NFX) encapsulated hydrogels exhibited good bactericidal properties with zone of inhibition of 19.2 ± 0.3 mm against E. coli and 16.4 ± 0.4 mm against S. aureus. The in-vitro release of NFX at pH 1.2 was 91 %, higher than pH 7.4 at 82 % with strong adherence to Higuchi kinetics model signifying that the release of NFX is via dissolution and diffusion. The release kinetics at different pH revealed Fickian behaviour establishing the potential of HS-CMC hydrogel for sustained release of norfloxacin.