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

Abstract

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.