Interaction of a polymeric biguanide biocide with phospholipid membranes |
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Authors: | T. Ikeda A. Ledwith C.H. Bamford R.A. Hann |
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Affiliation: | 1. Department of Inorganic, Physical and Industrial Chemistry, University of Liverpool, P.O. Box 147, Liverpool L69 3BX U.K.;2. Corporate Laboratory, Imperial Chemical Industry, P.O. Box 11, The Heath, Runcorn, Cheshire U.K. |
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Abstract: | 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. |
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Keywords: | DPPC DPPE egg PC egg yolk phosphatidylcholine egg PE egg yolk phosphatidylethanolamine egg PG phosphatidylglycerol prepared from egg PC PA phosphatidic acid PHMB poly(hexamethylene biguanide hydrochloride) DAHB diaminohexyl biguanide DAH 1,6-diaminohexane DPH 1,6-diphenyl-1,3,5-hexatriene DSC differential scanning calorimeter transition temperature (maximum peak height) degree of fluorescence polarization |
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