Effect of Deposition and Protease Digestion on the Ex Vivo Activity of Antimicrobial Peptide-Coated Contact Lenses

Parthasarathi Kalaiselvan*, Debarun Dutta, Nagaraju V. Konda, Savitri Sharma, Naresh Kumar, Fiona Stapleton, Mark D. P. Willcox*, Piersandro Pallavicini (Editor)

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


A clinical study of antimicrobial contact lenses containing the cationic peptide Mel4 was conducted. The few adverse events that occurred with this lens occurred on or after 13 nights of wear. The current study examined whether the Mel4 contact lenses lost activity during wear and the mechanism of this loss. Participants wore contact lenses for up to 13 nights. Lenses were tested for their ability to reduce the adhesion of Pseudomonas aeruginosa and Staphylococcus aureus. The amount of protein and lipid extracted from lenses was measured. The ability of trypsin to affect the antimicrobial activity of Mel4-coated contact lenses was measured. Mel4-coated contact lenses lost their antimicrobial activity at six nights of wear for both bacteria. The amount of lipids (13 ± 11 vs. 21 ± 14 μg/lens at 13 nights wear) and proteins (8 ± 4 vs. 10 ± 3 mg/lens at 13 nights of wear) extracted from lenses was not different between Mel4-coated and uncoated lenses, and was not different after three nights when antimicrobial activity was maintained and thirteen nights when they had lost activity (lipid: 25 ± 17 vs. 13 ± 11, p = 0.2; protein: 8 ± 1 vs. 8 ± 4 mg/lens, p = 0.4). Trypsin digestion eliminated the antimicrobial activity of Mel4-coated lenses. In summary, Mel4-coated contact lenses lost antibacterial activity at six nights of wear, and the most likely reason was proteolytic digestion of the peptide. Future studies will design and test proteolytically stable peptide mimics as coatings for contact lenses.
Original languageEnglish
Article number349
Number of pages13
Issue number2
Publication statusPublished - 14 Jan 2023

Bibliographical note

Funding Information:
This research was funded by NHMRC ideas grant APP1183597, NHMRC development grant APP1076206 and a grant from CooperVision, Pleasanton, CA, USA.

Publisher Copyright:
© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).


  • antimicrobial activity
  • antimicrobial contact lens
  • cationic peptide
  • clinical trial
  • deposition
  • Mel4
  • protease digestion


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