Mel4-coated hyaluronic acid-laden etafilcon A contact lenses: Improved wettability with retained antimicrobial properties

Abstract

Soft contact lenses are a common mode of vision correction used worldwide. However, contact lens wearers often experience discomfort and are at risk of developing microbial infections. To address these issues, we designed Mel4-coated hyaluronic acid-laden etafilcon contact lenses to improve wettability while providing antimicrobial properties. The process involved the interaction of the etafilcon lens, which carries a net negative charge, with positively charged Mel4 (a cationic antimicrobial peptide). This was followed by interaction with hyaluronic acid (a negatively charged polymer). The components were then crosslinked using EDC-NHS [N-(3-dimethyl aminopropyl)-N'-ethyl carbodiimide hydrochloride and N-Hydroxy succinimide] to form amide bonds between the compounds and the lens. In this study, four batches of lenses were prepared: the first consisted of conventional HA-soaked lenses (SM-HA-L), the second consisted of lenses soaked in Mel4 and HA (SM-Mel4-HA-L), the third batch consisted of HA crosslinked with the lens (HA-Cr-L), and the fourth consisted of lenses soaked in Mel4 and HA, followed by crosslinking (Mel4-HA-Cr-L). During the washing and sterilization steps, SM-HA-L lenses showed high leaching compared to SM-Mel4-HA-L lenses, while HA-Cr-L and Mel4-HA-Cr-L lenses showed no leaching. A hyaluronidase breakdown assay revealed 5.37 μg, 9.28 μg, 8.04 μg, and 6.07 μg of HA per lens for SM-HA-L, SM-Mel4-HA-L, HA-Cr-L, and Mel4-HA-Cr-L, respectively. The wettability (contact angle) of SM-Mel4-HA-L lenses was improved compared to HA-Cr-L and Mel4-HA-Cr-L lenses. In vitro release studies showed no leaching of HA, indicating permanent entrapment or binding of HA to the contact lens surface. Both the SM-Mel4-HA-L lenses and crosslinked Mel4-HA-Cr-L lenses could significantly reduce the adhesion of Pseudomonas aeruginosa 6294 and Staphylococcus aureus 31 to the lenses. In conclusion, the presence of HA improved wettability, while Mel4 retained its antimicrobial activity, highlighting its potential to advance existing contact lens technology with improved wettability and antimicrobial properties.

Keywords: Antimicrobial activity; Contact lens; Hyaluronic acid; Mel4 peptide; Optophysical properties; Wetting agent.