Abstract
Purpose: :
To compare the antimicrobial activity of LL-25, a truncated derivative of human cathelicidin LL-37, immobilized to surfaces by physisorption, carbodiimide and click chemistry.
Methods: :
LL-25 peptide was immobilized on to fluorous surfaces covalently by Cu-catalysed alkyne-azide cycloaddition ("click" reaction) and amidation (carbodiimide) or non-covalently by simple physisorption. Also in some experiments the click reaction was used to prepare LL-25 functionalised PAMAM dendrimers which were then immobilized on the fluorous surface. Surfaces were characterized by X-ray photoelectron spectroscopy, and peptide density was estimated using coomassie blue. Peptide modified surfaces were incubated with Pseudomonas aeruginosa (PA01) for 24 or 48 hrs (functionalized dendrimers) and the number of attached bacteria determined by colony forming assay.
Results: :
Peptide densities were 4.1±2.2; 20.9±0.2; 16.0±2.4 and 30.0±2.0 for physisorbed, carbodiimide, click and dendrimer-click modified fluorous surfaces respectively (n=3). Bacterial adhesion was reduced for all LL-25 modified fluorous surfaces compared to unmodified surfaces. Setting adhesion to unmodified surface as 100%, adhesion to click, carbodiimide and physisorbed surfaces was only 2±1%, 6±3% and 30±3% (n=4) respectively. Adhesion to click-modified surfaces was significantly lower than carbodiimide and physisorbed surfaces (p<0.018 and p<0.001 respectively, ANOVA). For dendrimer modified surfaces, bacterial adhesion was only 2±2% of adhesion to unmodified control surfaces (n=4).
Conclusions: :
Surfaces prepared by click chemistry had greatest antimicrobial activity likely because free amino groups important for antimicrobial activity are not involved in the immobilization reaction and greater freedom of movement of the immobilized peptide. LL-25 retains antimicrobial activity when covalently immobilized and has potential as an effective anti-microbial coating for biomedical devices such as contact lenses.
Keywords: antibiotics/antifungals/antiparasitics • contact lens • bacterial disease