Polymer multilayers loaded with antifungal β-peptides kill planktonic Candida albicans and reduce formation of fungal biofilms on the surfaces of flexible catheter tubes

Abstract

Candida albicans is the most common fungal pathogen responsible for hospital-acquired infections. Most C albicans infections are associated with the implantation of medical devices that act as points of entry for the pathogen and as substrates for the growth of fungal biofilms that are notoriously difficult to eliminate by systemic administration of conventional antifungal agents. In this study, we report a fill-and-purge approach to the layer-by-layer fabrication of biocompatible, nanoscale ‘polyelectrolyte multilayers’ (PEMs) on the luminal surfaces of flexible catheters, and an investigation of this platform for the localized, intraluminal release of a cationic β-peptide-based antifungal agent. We demonstrate that polyethylene catheter tubes with luminal surfaces coated with multilayers ~700 nm thick fabricated from poly-L-glutamic acid (PGA) and poly-L-lysine (PLL) can be loaded, post-fabrication, by infusion with β-peptide, and that this approach promotes extended intraluminal release of this agent (over ~4 months) when incubated in physiological media. The β-peptide remained potent against intraluminal inoculation of the catheters with C albicans and substantially reduced the formation of C albicans biofilms on the inner surfaces of film-coated catheters. Finally, we report that these β-peptide-loaded coatings exhibit antifungal activity under conditions that simulate intermittent catheter use and microbial challenge for at least three weeks. We conclude that β-peptide-loaded PEMs offer a novel and promising approach to kill C albicans and prevent fungal biofilm formation on surfaces, with the potential to substantially reduce the incidence of device-associated infections in indwelling catheters. β-Peptides comprise a promising new class of antifungal agents that could help address problems associated with the use of conventional antifungal agents. The versatility of the layer-by-layer approach used here thus suggests additional opportunities to exploit these new agents in other biomedical and personal care applications in which fungal infections are endemic.

Antifungal activity of a β-peptide in synthetic urine media: Toward materials-based approaches to reducing catheter-associated urinary tract fungal infections

“…We used two model biocompatible polyelectrolyte multilayer coating systems—a polypeptide-based system consisting of poly-L-lysine (PLL) and poly-L-glutamic acid (PGA) [37, 44–46], and a polysaccharide-based system consisting of hyaluronic acid (HA) and chitosan (CH) [38, 47–50] — to fabricate polymeric thin film coatings on the intraluminal walls of urinary catheters. Using a previously developed fill-and-purge method [37, 38], we fabricated PGA/PLL and HA/CH multilayers inside polyurethane, polyethylene, and silicone tubes commonly used to manufacture urinary catheters.…”

“…Using a previously developed fill-and-purge method [37, 38], we fabricated PGA/PLL and HA/CH multilayers inside polyurethane, polyethylene, and silicone tubes commonly used to manufacture urinary catheters. β-Peptide was loaded into the coated catheter tubes by infusing β-peptide 1 into the tubes and allowing it to infiltrate the coatings by diffusion for 24 hours (see Materials and Methods for additional details of β-peptide loading).…”

“…The tubes were then rinsed twice using a solution of NaCl (0.15 M) in water for 1 min each. PEM films were then deposited using a previously developed ‘fill-and-purge’ approach [37, 38]. Briefly, (i) a solution of negatively charged polymer (PGA or HA) was infused into the tube and allowed to incubate (for 3 min or 5 min, respectively), (ii) tubes were rinsed twice by infusing a rinse solution of NaCl solution in water (0.15 M) for 1 min each, (iii) tubes were infused with a solution of positively charged polymer (PLL or CH for 3 min or 5 min, respectively), and (iv) tubes were rinsed again in the manner described in step (ii).…”

“…Briefly, (i) a solution of negatively charged polymer (PGA or HA) was infused into the tube and allowed to incubate (for 3 min or 5 min, respectively), (ii) tubes were rinsed twice by infusing a rinse solution of NaCl solution in water (0.15 M) for 1 min each, (iii) tubes were infused with a solution of positively charged polymer (PLL or CH for 3 min or 5 min, respectively), and (iv) tubes were rinsed again in the manner described in step (ii). This was repeated until 19.5 PGA/PLL or HA/CH bilayers had been deposited (such that all films were terminated by the deposition of a final layer of the cationic polymer, as reported previously [37, 38]).…”

Technology-driven layer-by-layer assembly of nanofilms

“…Fluidic assembly can be used to deposit multilayers with fluidic channels, both by coating the channel walls and by coating a substrate placed or immobilized in a fluidic channel (77). The general method involves using pressure or vacuum to sequentially move polymer and washing solutions through the channels, which can be fluidic components, such as tubing or capillaries, or designed microfluidic networks (78,79). Flow-chamber-based QCM is a common fluidic assembly technology used for investigating thin-film properties and multilayer growth by providing crucial real-time information (22).…”