Development of non-toxic antibiofilm surfaces and albumin nanoparticles based on synergistic combinations of antimicrobial peptides and conventional antibiotics

Resumen

Antibiotic-resistance is considered a global threat by World Health Organization, which urged the development of new therapeutic strategies. With biofilms being the major cause of Healthcare-Associated Infections (HAI), attention is increasingly focused on finding therapies that target not only planktonic cells but also biofilms formed by resistant strains. Based on the potent antibiotic-enhancing activity of some antimicrobial peptides (AMPs), we aimed to develop non-toxic anti-biofilm surfaces and systems based on the combination of an AMP and a conventional antimicrobial. We hypothesized that polymyxin B nonapeptide (PMBN), could retain its potentiating activity upon covalent immobilization on the surface of a biomaterial (silicone) or as part of human serum albumin nanoparticles (HSA-NPs). Alternatively, the antibiotic sensitizing potential of PMBN was exploited by loading combinations of free PMBN and antibiotics into cyclodextrin-coated surfaces or HSA-NPs. The inhibitory and bactericidal activities of these experimental systems were assessed by viable counting, confocal microscopy, safranin uptake, checkerboard tests and time-kill assays. Using a multi-resistant clinical strain of P. aeruginosa (Ps4), we demonstrated that covalently immobilized PMBN: i, displayed kill-on-contact activity in combination with antibiotics added exogenously or incorporated into the silicone matrix and prevented biofilm growth; ii, enhanced the efflux pump inhibitor PaβN and further reduced the anti-biofilm minimum inhibitory concentration; iii, when conjugated to HSA, allows the preparation of antibiotic loaded NPs that are bactericidal and can eradicate mature biofilms. Moreover, we proved that PMBN and levofloxacin can be loaded into silicone-grafted γ-cyclodextrin and that this combination exerted a potent anti-biofilm activity upon its release. These findings may be applied to the development of medical devices resistant to biofilm formation. Keywords: biofilm, antimicrobial peptides, polymyxin B nonapeptide, anti-biofilm, nanoparticles.