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Rebecca Lace, Kyle George Doherty, Debarun Dutta, Mark Willcox, Rachel Williams; Addition of poly-ε-lysine or Mel4 peptides to contact lenses provides antimicrobial activity. Invest. Ophthalmol. Vis. Sci. 2019;60(9):2537.
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Adhesion of pathogens, such as bacteria, to contact lenses is a contributing factor to the development of microbial keratitis. Potential methods to inhibit bacterial adhesion include surface modification of existing contact lens material via antimicrobial peptide binding or development of new antimicrobial lens materials. We hypothesised that poly-ε-lysine (PεK) or Mel4 peptides covalently bound to either Acuvue2 lenses or novel PεK/suberic acid hydrogel lenses would have an antimicrobial activity against Pseudomonas aeruginosa in vitro.
Two PεK hydrogels were synthesised overnight by cross-linking suberic acid (SU) with PεK at 0.1mg/ml and 0.133mg/ml (named SU0.1 and SU0.133 respectively) using carbodiimide chemistry. After synthesis, PεK lenses and Acuvue lenses were incubated with either additional PεK peptide or Mel4 peptide at 3mg/ml in the presence of 250mM N-hydroxysuccinimide (NHS) and 1-Ethyl-3-(3-dimethylaminopropyl)carbodIimide (EDC) for 2.5hrs. Lenses were inoculated with 1x106 CFU of P. aeruginosa 6294 for 18hrs. Lenses were vortexed and the slurry was serially diluted for a viable plate count. After 24hrs viable bacteria were counted as CFU. One-way ANOVA with Dunnett’s T3 posthoc was performed, significance was considered at p<0.05.
Blank Su/PεK hydrogels had >0.5 log inhibition of bacteria (0.6±0.2 log for SU0.1, 0.7±0.1 log for SU0.133). This was a greater reduction than when Mel4 was covalently bound to PεK hydrogels. However, when additional PεK was bound to hydrogels a >3 log reduction was observed (3.1±1.7 log for SU0.1PεK, 3±1.6 log for SU0.133PεK), which was significantly different to all other treatments (p<0.05). The addition of Mel4 and PεK to Acuvue lenses resulted in 0.5±0.8 and 1.2±0.6 log reductions, respectively.
Mel 4 bound to PεK/SU or Acuvue lenses did not produce the antimicrobial activity as previously observed when Mel 4 was bound to commercial lenses, [Dutta et al. Biofouling 2016; 32: 429-438]. This may be due to a different binding method used in this study, inhibiting the antimicrobial activity of Mel4. The addition of PεK on both hydrogels demonstrated a large log reduction in P. aeruginosa. PεK bound to Acuvue lenses was more effective than Mel4, and displayed similar activity against P. aerginosa as Mel4 in previous work using an alternative binding method.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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