Amphiphilic Effects of Chlorhexidine Digluconate on Rotational and Lateral Mobilities of Bacterial Outer and Model Membrane Lipid Bilayers

Intramolecular excimer formation of 1,3-di(1-pyrenyl)propane (Py-3-Py), and fluorescence polarization of 1,6-diphenyl1,3,5-hexatriene(DPH) were used to investigate the effect of chlorhexidine digulconate (CHX) on the bulk fluidity of outer membranes (OPG) isolated from cultured Porphyromonas gingivalis and multilamellar vesicles were prepared with total lipids (OPGTL) extracted from OPG and prepared with mixture (PL) of DPPE and DPPC. The fluorescence polarization of n-(9-anthroyloxy)stearic acid (n-AS) were used to examined the effect of CHX on the rotational mobility of the surface and interior region of membrane lipid bilayers. CHX decreased the mobility of the surface region of bilayers but the drug increased the mobility of the interior region of membrane lipid bilayers.These indicate that CHX increased both the lateral and rotational mobilities of probes in OPG, OPGTL and PL bilayers. Selective quenching of Py-3-Py and DPH by TNBS was utilized to examine transbilayer fluidity asymmetry of OPG, OPGTL and PL lipid bilayers. CHX had a greater fluidizing effect on the inner monolayers as compared to the outer monolayer of OPG, OPGTL and PL lipid bilayers. The sensitivities to the increasing effect of fluidity differed according to these membrane lipid bilayers in the descending order of OPG, PL and OPGTL. CHX increased the rotational mobility of the hydrocarbon interior of OPG, OPGTL and PL but decreased the mobility of membrane interface of OPG, OPGTL and PL. The sensitivities to the increasing effects of CHX on the rotational mobility were in proportion to the located depths of the probes in descending order, as follows: 16-AP, 12-AS, 9-AS and 6-AS. The disordering or ordering effects of CHX on the membrane lipids might be responsible for some, but not all of its bateriostatic and bactericidal actions.