Amoebicidal Activity of Poly-Epsilon-Lysine Functionalized Hydrogels

PURPOSE. To determine the amoebicidal activity of functionalized poly-epsilon-lysine hydrogels (p epsilon K+) against Acanthamoeba castellanii. METHODS. A. castellanii trophozoites and cysts were grown in the presence of p epsilon K solution (0-2.17 mM), p epsilon K or p epsilon K+ 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 +/- p epsilon K, p epsilon K+ 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 p epsilon K+ hydrogels resulted in the death of 98.52% or 83.31% of the trophozoites at 24 hours or 7 days, respectively. The toxicity of p epsilon K+ 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 p epsilon K 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 p epsilon K+ hydrogels showed the absence of A. castellanii in the stroma, with no regrowth from corneas or p epsilon K+ hydrogel, compared with infected-only corneas and those incubated in presence of commercial hydrogel CL. CONCLUSIONS. p epsilon K+ hydrogels demonstrated pronounced amoebicidal and cysticidal activity against A. castellanii. p epsilon K+ hydrogels have the potential for use as CLs that could minimize the risk of CL-associated Acanthamoeba keratitis.