Study of ocular drug delivery system using drug-loaded liposomes

BACKGROUND: This project aims to formulate and characterize a drug-eluting contact lens to provide controlled release of drug for a longer period of time, using liposomes as drug delivery system. MATERIALS AND METHODS: Drug delivering contact lenses were created by coating disposable soft contact lenses with ciprofloxacin entrapped in the liposomes. Reverse phase evaporation and lipid film hydration methods were used for the preparation of ciprofloxacin trapping reverse phase evaporation vesicles, that is, unilamellar vesicles (REVs) and multilamellar vesicles (MLVs), respectively. Soya lecithin and cholesterol (CH) were used in the molar ratios of 7:4 and 7:2. The spherical structure of the liposomes, the mean diameter, and their purity were determined by photomicroscopic, transmission electron microscope, and chromatographic analysis, respectively. The prepared liposomes were evaluated for their entrapment efficiency, in vitro drug release, stability, and toxicity. RESULTS: MLVs were larger than REVs with their mean diameter 338.32 nm and also entrapped greater amount of ciprofloxacin. Drug loading and its release from the liposomal vesicles was dependent on CH content. Ciprofloxacin released from the liposomes coated on the contact lenses not only inhibited both Staphylococcus aureus and Pseudomonas aeruginosa on an agar plate but also showed an enhanced antibacterial effect as determined by minimal inhibitory concentrations. Approximately 40% of ciprofloxacin was retained up to a period of 3 months at 4°C. Furthermore, the formulation was found to be nontoxic and also a reduction in toxicity of ciprofloxacin was observed after entrapment when assessed by lymphocyte toxicity assay and chick embryo inoculation. CONCLUSIONS: An innovative drug delivery system consisting of drug-loaded liposomes coated onto the surface of contact lenses has been developed. This system is highly specific in terms of localized and sustained application of the drug.