Antimicrobial Activity of Cationic Conjugated Polyelectrolytes and Oligomers against Saccharomyces cerevisiae Vegetative Cells and Ascospores

Abstract

The antifungal activities of poly(phenylene ethynylene) (PPE)-based cationic conjugated polyelectrolytes (CPEs) and oligo-phenylene ethynylenes (OPEs) were investigated using Saccharomyces cerevisiae (S. cerevisiae) as a model pathogen. The effect of the CPE and OPE materials on the vegetative cells and ascospores were tested in the dark or with UV-irradiation. A number of the tested polymers and oligomers significantly reduced the viability of the vegetative yeast cells in the dark, with activities exceeding the commonly used antibiotic Amphotericin B. With UV-irradiation, all of the tested CPEs and OPEs exhibited potent antifungal activities and completely inactivated the yeast cells. In particular, the oligomeric EO-OPE-1(Th, C2) strongly inactivates ascospores with UV-light at a dose level lower than sporicidal agents reported in the literature. Under conditions that promote spore germination, the CPEs and OPEs show efficient activities against the germinated spores. The protein-enriched outer envelope of yeast cells and germinated ascospores appears to serve as a main target for the CPE and OPE antimicrobial materials.

Antifungal Properties of Cationic Phenylene Ethynylenes and Their Impact on β-Glucan Exposure

“…C. glabrata is noted for its resistance to killing by cationic antimicrobial peptides in comparison to C. albicans and other pathogenic Candida species (54)(55)(56). Furthermore, the decreased ability of EO-OPE-DABCO to kill C. glabrata resembles the results of a previous study, in which a 10-g/ml concentration of the compound failed to kill 99% of S. cerevisiae yeast cells, even after an hour in the light (23). Although S. cerevisiae is benign, it is closely related to C. glabrata (32,36).…”

“…A subset of conjugated polyelectrolytes, phenylene ethynylenes, have shown promising biocidal activity against Gram-positive and -negative bacterial pathogens, as well as the environmental yeast Saccharomyces cerevisiae (21)(22)(23). The chemical structure of these compounds renders them capable of inducing broad-spectrum cell damage.…”

Controlling macromolecular structures towards effective antimicrobial polymers

“…Many types of antimicrobial polymers based on poly(phenylene ethynylene) cationic conjugated polyelectrolytes were investigated by Whitten and co-workers [85]. In a recent study, antifungal activity of poly(phenylene ethynylene) polyelectrolytes (Table 2F) and oligo-phenylene ethynylenes were investigated [81]. The polycations effectively inhibited the fungus Saccharomyces cerevisiae, an opportunistic human pathogen, both in the dark and under ultraviolet (UV)/visible light irradiation.…”

“…They investigated telechelic antimicrobial function of poly(-oxazoline)s to reveal the influence of different non-active SGs distal S. cerevisiae >6-log reductions [81] to the cationic end groups on the antimicrobial effect (Table 4B) [98]. They found that the antimicrobial activity can be controlled over several orders of magnitude, illustrating the fact that hydrophilic SGs with necessary length activate the biocidal group while nonbasic hydrophilic groups deactivate it.…”

Poly(para-phenylene ethynylene) (PPE)- and poly(para-phenylene vinylene) (PPV)-poly[(2-(methacryloyloxy)ethyl) trimethylammonium chloride] (PMETAC) graft copolymers exhibit selective antimicrobial activity

“…11,12 It has been shown that the addition of charged pendants to conjugated polymers has led to enhanced antibacterial activity, with both components seemingly necessary for potent acitvity. 13,14 In some instances it has been shown that the conjugated backbone allows UV activation pathways resulting in alternative killing mechanisms which in combination with the charged pendants increases activity. 12,14 Polyphenylene ethynylene (PPE) derivatives with positively charged quaternary ammonium (QA) or alkylpyridinium or negatively charged sulfonate pendants have been found to be active against both Gram-negative and Gram-positive bacteria.…”