Antibacterial and Antifungal Activities of Poloxamer Micelles Containing Ceragenin CSA-131 on Ciliated Tissues

Abstract

Ceragenins were designed as non-peptide mimics of endogenous antimicrobial peptides, and they display broad-spectrum antibacterial and antifungal activities, including the ability to eradicate established biofilms. These features of ceragenins make them attractive potential therapeutics for persistent infections in the lung, including those associated with cystic fibrosis. A characteristic of an optimal therapeutic for use in the lungs and trachea is the exertion of potent antimicrobial activities without damaging the cilia that play a critical role in these tissues. In previous work, potent antimicrobial activities of ceragenin CSA-131 have been reported; however, we found in ex vivo studies that this ceragenin, at concentrations necessary to eradicate established biofilms, also causes loss of cilia function. By formulating CSA-131 in poloxamer micelles, cilia damage was eliminated and antimicrobial activity was unaffected. The ability of CSA-131, formulated with a poloxamer, to reduce the populations of fungal pathogens in tracheal and lung tissue was also observed in ex vivo studies. These findings suggest that CSA-131, formulated in micelles, may act as a potential therapeutic for polymicrobial and biofilm-related infections in the lung and trachea.

Keywords: antibacterial activity; antifungal activity; biofilm; ceragenin; cilia; micelles; poloxamer.

Figure 1

Structure of ceragenin CSA-131.

Figure 2

Antibiofilm results determined through the plating of microorganisms freed from biofilms, culturing, and plate counting. White bars: S. aureus (ATCC 25923); black bars: P. aeruginosa (ATCC 47085); gray bars: C. albicans (ATCC 90028); hashed bars: C. auris (CDC 384). Detection limit: 2 logs. * indicates p < 0.05 relative to controls and to pluronic alone.

Figure 3

Antibiofilm results determined through colorimetric (XTT) assay represented as percent survival. White bars: S. aureus (ATCC 25923); black bars: P. aeruginosa (ATCC 47085); gray bars: C. albicans (ATCC 90028); hashed bars: C. auris (CDC 384). * indicates p < 0.05 relative to controls.

Figure 4

Kinetic antibacterial activity against P. aeruginosa of CSA-131 (100 µg/mL) (black squares), CSA-131 (100 µg/mL) with pluronic (4%) (black triangles); untreated control (black diamonds). Detection limit was two logs.

Figure 5

Description of methods used in harvesting and testing porcine trachea explants.

Figure 6

SEM images of cilia on porcine trachea explants untreated, treated with CSA-131 at 100 µg/mL, and treated with CSA-131 at 100 µg/mL with 4% pluronic. Exposed goblet cells are circled in the image of the sample treated with CSA-131 without pluronic.

Figure 7

Fungi remaining in tissue explants after incubation for two hours followed by treatment with CSA-131 (with and without pluronic (4% or 5%) for one hour. White bars: C. albicans (ATCC 90028); black bars: C. auris (CDC 384). (A) trachea explants; (B) lung explants.