Chitosan-cross-linked tannic acid with hibiscus flower extract nanocomposite gel for ocular drug delivery against bacterial keratitis

Bacterial keratitis is a serious ocular infection caused by microorganisms, which affects more significantly the anterior segment of the eye and, in turn, inflames the cornea. In the present investigation, we developed a biopolymer-based ocular nanocomposite gel formulation (CH@TA@HE) having hibiscus extract (HE) loaded in chitosan (CH), cross-linked with tannic acid (TA). Several characterization techniques were carried out to validate nanocomposite formulation. The absorption maxima and encapsulation efficiency of HE and TA were determined by UV–Vis spectroscopy, while particle size analysis was done by DLS. Stability was assessed by zeta potential measurements, whereas functional groups were analyzed by FTIR. In vitro and ex vivo studies were carried out to understand the efficacy of ocular nanocomposite gel formulation. Size of nanocomposite was 58.75 nm, measured using HR-TEM. SAED pattern confirmed nanocomposites amorphous nature. DPPH scavenging activity of formulation was found to be 76.93%, and the biocompatibility assays indicated the formulation safe for ocular application. Drug release studies demonstrated ocular tolerance, maximum penetration, and sustained delivery of the encapsulated bioactive components. Moreover, the formulation exhibited prominent growth inhibition and anti-biofilm activity against bacterial strains. Ex vivo histological studies on ocular tissues to understand pathological changes induced by bacteria and the therapeutic potential of nanocomposite was studied. Results indicate CH@TA@HE ocular nanocomposite gel formulation to be promising and potential candidate for management of bacterial keratitis. Further in vivo studies can provide an insight about the mechanism of protective effect of nanocomposite gel.