Abstract
Purpose:
Immobilisation of antimicrobial peptides (AMP) such as melimine onto contact lenses can produce antimicrobial surfaces. This study aimed to evaluate compatibility of the melimine-coated lenses with three multipurpose disinfection solutions (MPDS).
Methods:
Melimine was covalently immobilised onto contact lens (etafilcon A) surfaces via EDC coupling. Retention of antimicrobial activity of melimine contact lenses against Pseudomonas aeruginosa 6294 and Staphylococcus aureus 31 was investigated after soaking for 1 day, 10 days and 30 days with MPDS or phosphate buffer saline (PBS; as control). Lenses were soaked with 2 ml of these solutions in storage cases and solutions were replaced daily with another 2 ml of fresh solutions. Antimicrobial activity was evaluated by viable plate count. In addition, lens surfaces were characterised by XPS to determine the elemental composition, especially for the presence of amide nitrogen which represents peptide.
Results:
Melimine lenses soaked with Biotrue™ or RevitaLens OcuTec™ showed retention of high antimicrobial activity against both the bacteria throughout the experiment (> 2 log inhibition), similar to the PBS soaked lenses. However, lenses soaked in OPTI-FREE® PureMoist® showed no antimicrobial activity. After soaking with PBS, Biotrue or RevitaLens lens surfaces were shown to contain amide nitrogen (~1.6 atom%) at a level comparable with un-soaked melimine-coated lenses (1.7 atom%). However, the amide nitrogen signal was very low (0.2 atom%) for PureMoist soaked lenses and at levels similar to uncoated lenses.
Conclusions:
Melimine lenses retained high activity after soaking with saline Biotrue or Revitalens for up to a month, showing that they are compatible with these MPDS. However, soaking in PureMoist reduced the level of melimine on the lens surface. Presence of surface wetting macromolecules such as EOBO in PureMoist may interact or mask tethered surface antimicrobials.
Keywords: 477 contact lens •
557 inflammation