Amoebicidal Activity of Poly-Epsilon-Lysine Functionalized Hydrogels

PURPOSE: To determine the amoebicidal activity of functionalized poly-epsilon-lysine hydrogels (pɛK(+)) against Acanthamoeba castellanii. METHODS: A. castellanii trophozoites and cysts were grown in the presence of pɛK solution (0–2.17 mM), pɛK or pɛK(+) hydrogels, or commercial hydrogel contact lens (CL) for 24 hours or 7 days in PBS or Peptone-Yeast-Glucose (PYG) media (nutrient-deplete or nutrient-replete cultures, respectively). Toxicity was determined using propidium iodide and imaged using fluorescence microscopy. Ex vivo porcine corneas were inoculated with A. castellanii trophozoites ± pɛK, pɛK(+) hydrogels or commercial hydrogel CL for 7 days. Corneal infection was assessed by periodic acid–Schiff staining and histologic analysis. Regrowth of A. castellanii from hydrogel lenses and corneal discs at 7 days was assessed using microscopy and enumeration. RESULTS: The toxicity of pɛK(+) hydrogels resulted in the death of 98.52% or 83.31% of the trophozoites at 24 hours or 7 days, respectively. The toxicity of pɛK(+) hydrogels resulted in the death of 70.59% or 82.32% of the cysts in PBS at 24 hours or 7 days, respectively. Cysts exposed to pɛK(+) hydrogels in PYG medium resulted in 75.37% and 87.14% death at 24 hours and 7 days. Ex vivo corneas infected with trophozoites and incubated with pɛK(+) hydrogels showed the absence of A. castellanii in the stroma, with no regrowth from corneas or pɛK(+) hydrogel, compared with infected-only corneas and those incubated in presence of commercial hydrogel CL. CONCLUSIONS: pɛK(+) hydrogels demonstrated pronounced amoebicidal and cysticidal activity against A. castellanii. pɛK(+) hydrogels have the potential for use as CLs that could minimize the risk of CL-associated Acanthamoeba keratitis.