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N. Cole, R. Chen, J. Park, N. Kumar, M. D. P. Willcox; Comparison of Attachment Strategies to Surfaces for Antimicrobial Cationic Peptides. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1983.
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Contact lens-associated adverse responses such as microbial keratitis and contact lens-induced acute red eye (CLARE) have been associated with bacterial colonisation of contact lenses. Prevention of the association of bacteria with the contact lens using an antimicrobial surface coating has been explored. We have developed a cationic peptide with broad-spectrum antimicrobial activity and good biocompatibility. However, to develop its use as an antimicrobial coating it must retain activity when covalently attached to a surface. These experiments explore efficacy modulation of peptides protamine and melamine upon covalent attachment to a surface.
Two photo-chemical attachment strategies using either 4-azidobenzoic acid (ABA) or 4-fluoro-3-nitrophenyl azide (FNA) to modify surfaces enabling the attachment of the peptides were examined. The successful modification of the surfaces was confirmed by XPS, SEM, contact angle measurements and fluorescence spectroscopy. The effectiveness of the peptide coatings against P. aeruginosa and S. aureus was examined by SEM and differential fluorescent staining of bacteria.
Fluorescence imaging showed successful attachment of the peptides to the surfaces. XPS analysis of both surfaces showed an approximately 5% increase in atomic nitrogen for protamine and a 3% increase for melimine indicating similar molar densities for both peptides with both chemistries. Contact angle measurement showed that the surfaces coated with melimine were more hydrophilic than those with protamine. Differential fluorescent staining of the bacteria showed that ABA coating with protamine resulted in less bacterial killing on the surface than the FNA attachment in spite of similar molar densities. Similarly, while melimine-coated samples showing good activity against both bacterial species attachment strategies differed in antimicrobial potential with the FNA chemistry showing fewer live cells adherent than the ABA chemistry. Further, melimine coating was more successful at preventing biofilm development over 48 hours than protamine.
The peptide melimine retained broad-spectrum efficacy when attached covalently to a surface, but surface attachment chemistry must be considered in order to retain maximal peptide antimicrobial activity.
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