Levofloxacin-loaded silicone contact lenses materials for ocular drug delivery

Silicone contact lenses (SCL), as an emerging ocular drug delivery system, achieve controlled drug release. However, the existing drug loading methods have limitations such as low drug uptake, complicated operation process, poor welling rate and transmittance of the lens after drug loading. In this study, an effective microemulsion soaking method was proposed to increase the drug-loading capacity of silicone contact lenses. Levofloxacin (LVF) was encapsulated into the microemulsion by direct agitation, then the microemulsion was loaded into silicone contact lenses using the immersion method. The adsorption capacity of levofloxacin and its effect on drug release kinetics were explored. The results showed that the particle size of the microemulsion was approximately 160 nm. The levofloxacin microemulsion soaking method (LVF-ME-SCL) significantly enhanced the drug loading of levofloxacin in the silicone contact lenses, achieving a maximum drug loading of 216.32 ± 1.15 μg/lens (p > 0.05). The total release rate of levofloxacin was 95.96% when the sustained release time was 10 h, and the drug leakage observed after 10 h was negligible. The survival rate of E. coli and S. aureus in LVF-ME-SCL-1 (LVF concentration was 4.8 mg/mL) group was 0 and 19.33 ± 0.02% (p < 0.0001), with a significant difference, indicating that the drug-loaded silicone contact lenses exhibited effective bactericidal properties against E. coli and S. aureus. Following the addition of maximum levofloxacin, the surface contact angle of silicone contact lenses decreased significantly to 32.88 ± 1.19° (p > 0.05), while the swelling, mechanical properties, and oxygen permeability remained relatively unchanged. There was no significant decrease in the transmittance of the contact lenses after the addition of levofloxacin, which remained above 95%. In conclusion, these results show that the microemulsion impregnation method effectively improves the drug loading and sustained release time of levofloxacin, and maintains lens performance stability before and after drug loading, so it is expected to be used in ophthalmic treatment.