Development of a Poly-ε-lysine Contact Lens for Drug Delivery in the Management of Fungal Keratitis

Abstract

Purpose : Fungal keratitis is challenging to treat. Antifungal drops are an inefficient means for drug delivery to the cornea with less than 7% of the drug reaching the site of infection. We developed a contact lens capable of sustained drug release to overcome this.

Methods : Amphotericin B (AmpB) was associated with a high-water content, transparent poly-ε-lysine (pεK) hydrogel with and without neutralisation (-NH₂ / -NH₃Cl) at 0-30 μg cm^-3. Fungicidal effect against Candida albicans, including in the presence of 10% horse serum, was assessed at 18 and 42 h by optical density (OD₆₀₀) and growth on agar. Tear film dilution effect was mimicked by storage of AmpB pεK gels in 0.1 cm³-3.4 cm³ sterile PBS for 24 h prior to fungal incubation. Drug elution over 96 h was evaluated by high performance liquid chromatography (HPLC) and drug stability was tested whilst associated with the gel by OD₆₀₀ up to 48 h. Lack of cytotoxicity of the AmpB pεK gels towards the HCE-T corneal epithelial cell line was assessed over 3 days. Statistical analysis was performed using two way ANOVA with Tukey post-hoc analysis and one way univariate AVOVAs.

Results : Neutralised AmpB -NH₂ pεK gels show improved fungicidal activity (p <0.005), and a longer (up to 72 h) drug release-profile above therapeutic levels (0.188 μg cm^-3) compared to AmpB -NH₃Cl pεK gel (p <0.005). Both pεK gels demonstrate fungicidal activity in normal conditions at 18 h: AmpB -NH₂ (0.057 OD₆₀₀, SD 0.003, p <0.005) and AmpB -NH₃Cl (0.227 OD₆₀₀, SD 0.340, p <0.005). Additionally, AmpB -NH₂ pεK gels did so at even low concentrations of AmpB (3 μg cm^-3) in the presence of horse serum at 18 h (0.048 OD₆₀₀, SD 0.003, p <0.005). ‘Tear dilution’ resulted in significantly less inhibition of fungal growth from AmpB -NH₃Cl pεK gels at 3 and 5 μg cm^-3 Amp B (p <0.005), but had no effect on the action of AmpB -NH₂ pεK gels. Neither the AmpB -NH₂ or -NH₃Cl pεK gels were cytotoxic to the HCE-T cell line, suggesting their potential for in vivo use as a contact lens.

Conclusions : AmpB -NH₂ pεK gels confer sustained therapeutic antifungal activity for at least 48 h without corneal epithelial cytotoxicity. Used as a drug delivery bandage contact lens this could avoid the need for intensive topical medication in the treatment of fungal keratitis.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.