Interaction of O-acylated chitosans with biomembrane models: Probing the effects from hydrophobic interactions and hydrogen bonding

Understanding the biocide action of poly(hexamethylene biguanide) using Langmuir monolayers of dipalmitoyl phosphatidylglycerol

“…The molecular-level interactions through which such effects take place include hydrophobic interactions with DPPG chains and dehydration of C O groups from DPPG. Surprisingly, the expected electrostatic interactions between the positively charged groups from PHMB and the phosphate groups from DPPG did not cause significant changes in the phosphate bands in the PM-IRRAS spectra, in contrast to what has been reported for chitosans interacting with dimyristoyl phosphatidic acid (DMPA) and dipalmitoyl phosphatidyl choline (DPPC) [20,22]. Therefore, it seems that hydrophobic interactions and dehydration may be as important as the electrostatic interactions reported by Ikeda et al [5] as the governing forces for increasing fluidity and permeability of the membrane involved in the biocide action of polyhexanides.…”

“…This shift is related to dehydration of carbonyl groups owing to interactions between C O groups from DPPG and NH groups from PHMB. Similar results were found for the interaction between chitosan derivatives and phosphate groups from phospholipids in Langmuir monolayers [22]. Dehydration of polar groups has also been found by Sautrey et al [33] in molecular-level interactions between an antimicrobial calixarene with guanidine groups, named CX1, and 1,2-dimyristoyl sn-glycero 3-phosho-rac-(1-glycerol) (DMPG).…”

“…The importance of the charge for biocide activity in these positively charged materials has been proven beyond doubt, but evidence has been mounting from Refs. [8,22] and from the present results that hydrophobic interactions are also crucial, especially for antimicrobial peptides acting through the barrel-stave pore model mechanism [8]. In particular, the hydrophobic core of the cell membrane must be disrupted, which normally occurs via changes in the membrane elasticity.…”

“…Here we employed the Langmuir-Blodgett technique [13][14][15][16] that allows for fabrication and manipulation of monomolecular films [17,18]. A Langmuir phospholipid monolayer may simulate half the biological membrane, producing a bioinspired interface [19], with which interactions can be studied [20][21][22][23], particularly with the assistance of the spectroscopic tool referred to as polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS). Since PHMB is soluble in water, we used solutions as a subphase under two conditions: in a phosphate buffer at pH 7.4 to mimic physiological condition, and in a Theorell buffer at pH 3.0, so that we can compare the results with those reported for chitosans.…”

Chitosan does not inhibit enzymatic action of human pancreatic lipase in Langmuir monolayers of 1,2-didecanoyl-glycerol (DDG)

“…Other components employed in monolayers included stearic acid and cholesterol [49][50][51]. From these studies, one can infer that the positively charged chitosans interact more strongly with negatively charged phospholipids, though hydrophobic interactions also play an important role [52,53].…”