title: Understanding the biocide action of poly(hexamethylene biguanide) using Langmuir monolayers of dipalmitoyl phosphatidylglycerol.
abstract: The disinfectant activity of poly(hexamethylene biguanide) (PHMB) has been explored in industrial applications, in agriculture and in food manipulation, but this biocide action is not completely understood. It is believed to arise from electrostatic interactions between the polyhexanide group and phosphatidylglycerol, which is the main phospholipid on the bacterial membrane. In this study, we investigated the molecular-level interactions between PHMB and dipalmitoyl phosphatidylglycerol (DPPG) in Langmuir monolayers that served as cell membrane models. PHMB at a concentration of 2×10(-4) g L(-1) in a Theorell-Stenhagen at pH 3.0 and in a phosphate at pH 7.4 was used as a subphase to prepare the DPPG monolayers. Surface pressure-area isotherms showed that PHMB adsorbs and penetrates into the DPPG monolayers, expanding them and increasing their elasticity under both conditions examined. Results from polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) indicated that PHMB induces disorder in the DPPG chains and dehydrates their C=O groups, especially for the physiological medium. Overall, these findings point to hydrophobic interactions and dehydration being as relevant as electrostatic interactions to explain changes in membrane fluidity and permeability, believed to be responsible for the biocide action of PHMB.
authors.affiliation: São Carlos Institute of Physics, University of São Paulo (USP), PO Box 369, São Carlos, SP 13566-590, Brazil. Electronic address: adriano_lsouza@hotmail.com.
authors.forename: Adriano L
authors.initials: AL
authors.lastname: Souza
authors.affiliation: Institute for Environmental, Chemical and Pharmaceutical Sciences, Federal University of São Paulo (UNIFESP), Diadema, SP 09972-270, Brazil.
authors.forename: Lucinéia F
authors.initials: LF
authors.lastname: Ceridório
authors.affiliation: Embrapa Instrumentation, National Nanotechnology Laboratory for Agribusiness (LNNA), São Carlos, SP 13560-970, Brazil.
authors.forename: Gustavo F
authors.initials: GF
authors.lastname: Paula
authors.affiliation: Embrapa Instrumentation, National Nanotechnology Laboratory for Agribusiness (LNNA), São Carlos, SP 13560-970, Brazil.
authors.forename: Luiz H C
authors.initials: LH
authors.lastname: Mattoso
authors.affiliation: São Carlos Institute of Physics, University of São Paulo (USP), PO Box 369, São Carlos, SP 13566-590, Brazil.
authors.forename: Osvaldo N
authors.initials: ON
authors.lastname: Oliveira
mesh_terms: D001645:Biguanides / Q000494:pharmacology*; D010715:Phosphatidylglycerols / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D001645:Biguanides; D010715:Phosphatidylglycerols; C031233:polihexanide; C030345:1,2-dipalmitoylphosphatidylglycerol
keywords: Antimicrobial activity; Biocide action; PHMB; PM-IRRAS spectroscopy; Phospholipid monolayers; Poly(hexamethylene biguanide)