Development and characterization of stimuli-responsive levofloxacin in situ gel for treatment of bacterial keratitis

Abstract

Purpose : In situ gels can undergo rapid sol-to-gel transformation triggered by external stimuli such as ions, temperature, and pH. The aim of this study is to develop an in-situ gelling system for the effective delivery and sustained-release of levofloxacin in the treatment of anterior corneal infections.

Methods : Varying concentrations of trigger-sensitive polymers, sodium alginate (SA) and hydroxypropyl methylcellulose (HPMC) were used to formulate in-situ gels (ISGs) with formulation codes F1-F12. The ISGs were evaluated for clarity, pH, gelling capacity, drug content, release kinetics and antimicrobial properties against gram negative organisms, Escherichia coli and Pseudomonas aeruginosa and gram-positive organisms, Streptococcus pneumoniae and Staphylococcus aureus using the Kirby-Bauer disk diffusion method. The irritability and toxicity of select ISGs were assessed using the Hen’s Egg Test, Chorioallantoic Membrane (HETCAM) assay.

Results : The ISGs were within pH range of 5.86 and 7.60. Formulation F7 (0.5% SA + 1.5% HPMC) had the highest gelling capacity in 0.11% CaCl.2H₂O with gelling time of 5 seconds, and the highest inhibition zone of 60.7 ± 1.15 mm against S. aureus. Formulation F11 (1.5% SA + 1.5% HPMC) had the highest zone of inhibition (ZOI) of 38.7 ± 2.31 mm against P. aeruginosa, Formulation F 2 (1% SA + 0.5% HPMC) had the highest ZOI of 47.3 ± 1.15 mm against S. pneumonia and 0.5% w/v LVF (control) had the highest ZOI against E. coli, 30.0 ± 2.00. Formulation F6 (1% HPMC + 1% SA) had the slowest release with approximately 60% release after 4 h, formulation F11 (1.5% HPMC + 2% SA) had the fastest release of 72% after 4 h while LVF solution (control) released 70% in 1 h. There was no significant (p > 0.05) change in the concentration of levofloxacin ISGs after storage at 25^o C for 60 days. The optimized ISGs with the highest concentration of stimuli responsive polymers (F4, F8 and F12) were found to be non-irritant with a test score of zero in the ocular HET-CAM test and drug release was by diffusion as confirmed from the highest R² value for the higuchi model.

Conclusions : Levofloxacin in-situ gels formulated with sodium alginate and HPMC E5 LV has been shown to sustain the release of levofloxacin over 8 h compared to the solution and is effective against bacterial infections caused by the tested gram-positive and gram-negative bacteria.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.