Biocidal Polymers Research Articles

Biocidal polymers active by contact. II. Biological evaluation of polyurethane coatings with pendant quaternary ammonium salts

AbstractFilms of polyurethane were prepared by reaction of hydroxytelechelic polybutadienes carrying covalently bound quaternary ammonium salts with an aliphatic triisocyanate. These coatings exhibited high biocidal activity against Gram‐positive and Gram‐negative bacteria, yeasts, and moulds. It was found that many parameters controlled the bioactivity such as the time of contact between films and bacteria, the [NCO]/[OH] ratio used to prepare the cured polyurethane, the concentration of quaternary ammonium salts in the coating, and the length of the alkyl chain from C8 to C16 linked to the quaternary nitrogen atom. A secondary phenomenon of diffusion only observed with the shorter alkyl chains (C8 and C10) was shown to be due to synthesis residues. After these water‐soluble impurities are eliminated, the biocidal activity remains excellent: then it is due only to a contact polymer bacteria. © 1993 John Wiley & Sons, Inc.

Polycationic biocides with pendant active groups: molecular weight dependence of antibacterial activity.

Two types of polycations with pendant active groups were synthesized: one is polymethacrylate containing pendant biguanide units, and the other is poly(vinylbenzyl ammonium chloride). The two polycations were found to exhibit higher bactericidal activity against Staphylococcus aureus than the corresponding monomers. Fractionation of the polycations was successfully performed on gel filtration chromatography, and examination of the antibacterial activity against S. aureus of the well-characterized polymer samples with various molecular weights (MW) revealed that the activity was strongly dependent on the MW of the polycations and that there existed an optimal MW range for the cidal action of the polymeric biocides. Experiments on the lysis of protoplasts of Bacillus subtilis in contact with the polycations have shown that target sites of the polycationic biocides are cytoplasmic membranes of bacteria.

Spectroscopic Studies on the Interaction of Polymeric In-chain Biguanide Biocide with Phospholipid Membranes as Probed by 8-Anilinonaphthalene-l-sulfonate

Abstract Interaction of a highly effective polymeric biocide poly(hexamethylene biguanide hydrochloride)(PHMB) with phospholipid model membranes was investigated spectroscopically by using 8-anilinonaphthalene-l-sulfonate (ANS) as a fluorescent probe. PHMB enhanced the fluorescence intensity and shifted the maximum wavelength of fluorescence of ANS embedded in the negatively-charged liposome composed of egg PC and dicetyl phosphate, while it had only small effect on the neutral liposome composed of egg PC alone. These results were interpreted in terms of preferred binding of PHMB to negatively-charged species. The Benesi-Hildebrand type plots revealed that PHMB was adsorbed to a greater extent onto the negatively-charged membrane than onto the neutral membrane: the dissociation constants for the liposome–ANS complexes derived from the plots gave quantitative evidence for the enhanced binding of PHMB to the negatively-charged membrane. Diaminohexyl biguanide (DAHB), a corresponding monomer to PHMB, was found to have no significant effect on either the neutral nor the negatively-charged liposome, a finding probably related to the fact that DAHB is practically inactive.

New polymeric biocides: synthesis and antibacterial activities of polycations with pendant biguanide groups.

Acrylate monomers with pendant biguanide groups were successfully synthesized, and their homopolymers and copolymers were prepared with acrylamide. These cationic disinfectants of polymeric forms exhibited high antibacterial activity against gram-positive bacteria, whereas they were less active against gram-negative bacteria. It was found that the activity of the polymeric disinfectants was much higher than that of the monomeric species, and the difference in activity between the polymers and the monomers was discussed on the basis of their contributions to each elementary process of the lethal action.

Interaction of a polymeric biguanide biocide with phospholipid membranes

Differential scanning calorimetry (DSC) and fluorescence polarization methods have been used to study the interactions between phospholipid membranes and a polymeric biocide, poly(hexamethylene biguanide hydrochloride) (PHMB). It was found that PHMB had very little effect on neutral lipids such as phosphatidylcholine (PC) and phosphatidylethanolamine (PE), whereas it greatly reduced the phase transition temperature of phosphatidylglycerol (PG), an acidic lipid found in bacteria. Although the corresponding monomeric biocide had a similar effect on the PG bilayer, the behaviour towards mixed lipid bilayers of PC and PG has been shown to be completely different for the polymeric and monomeric biocides: viz. the former can induce isothermal phase separation into a PHMB-PG complex domain and a PC-enriched domain, whilst the latter cannot. This may account for the great difference in bactericidal activity between them. It is suggested that PHMB interacts primarily with negatively charged species in the membranes, inducing aggregation of acidic lipids in the vicinity of the adsorption site, where higher fluidity and higher permeability are expected. The results have shown that two factors might be crucial in the cidal activity of such types of cationic disinfectants as biguanides: phase separation and interaction with the hydrocarbon interior of the membranes. Polymeric biocides could be particularly effective by virtue of their ability to combine hydrophobic character and multiple charges within a single molecule.

Interaction of biologically active molecules with phospholipid membranes: I. Fluorescence depolarization studies on the effect of polymeric biocide bearing biguanide groups in the main chain

Interaction of poly(hexamethylene biguanide hydrochloride) (PHMB), which is a polymeric biocide bearing biguanide groups in its main chain, with phospholipid bilayers was studied by the fluorescence depolarization method. A strong interaction of PHMB with negatively charged bilayers composed of phosphatidylglycerol(PG) alone or of PG and phosphatidylcholine (PC) was observed, whereas neutral PC bilayers were not affected. On adding PHMB, the fluorescence polarization of diphenylhexatriene embedded in the negatively charged bilayers was reduced to a great extent, especially in the gel phase. This was interpreted in terms of PHMB-induced expansion and fluidization of the bilayer, which enables the probe molecule to undergo less-hindered torsional motion. Similarity between PHMB and polymyxin B in the structure, the mode of action against bacteria and the interaction with lipid membranes is discussed.