Chitosan−Cholesterol and Chitosan−Stearic Acid Interactions at the Air−Water Interface

Abstract

We report in this work the isotherms of cholesterol and stearic acid at the air-water interface modified by different chitosans (chitosan chloride, hydrophobic modified chitosan, and medium and high molecular weight chitosans) in the aqueous subphase. The Langmuir-Blodgett films of the complexes cholesterol-chitosan and stearic acid-chitosan are analyzed by atomic force microscopy (AFM), and a molecular simulation was performed to visualize the chitosan-lipid interactions. Strong modifications are obtained in the isotherms as a result of the chitosan interactions with cholesterol and stearic acid at the air-water interface. These modifications were dependent on the type and concentration of chitosan. Severe modifications of all phases were noticed with larger molecular areas, and the observed changes in the compressional modulus were dependent on the type of chitosan used. The complexes of chitosan-stearic acid were more flexible than the ones of chitosan-cholesterol. The AFM images demonstrated that chitosan was disaggregated by the cholesterol and stearic acid interactions producing more homogeneous surfaces in some cases. The hydrophobic chitosan showed more affinity with stearic acid, while both medium and high molecular weight chitosans produced homogeneous surfaces with cholesterol. The simulated chitosan chains interacting with cholesterol and stearic acid demonstrated the possibility of specific sites of electrostatic bonds between these molecules. Adsorption of cholesterol on the different powdered chitosans, performed by HPLC, showed that the medium and high molecular weight chitosans could retain higher proportions of cholesterol compared with the other analyzed samples.

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

“…Accordingly, the resulting surface pressure-area isotherm for this higher chitosan concentration is more expanded. This ability of chitosan to expand DDG monolayers is consistent with the literature, for such expansion has been observed for several surfactants, including lipids or phospholipids such as stearic acid, oleic acid, linoleic acid, ␣-linoleic acid, cholesterol, dipalmitoylphosphatidylglycerol (DPPG), dipalmitoylphosphatidylcholine (DPPC) and dimyristoylphosphatidic acid (DMPA) [42][43][44][49][50][51]. The maximum C S −1 (C S −1 max ) can be used to characterize the surface packing of the monolayers [60].…”

“…Two main representative phospholipids used were phosphatidylglycerol and phosphatidylcholine to mimic bacterial and mammalian membranes [46][47][48], respectively. 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].…”

Global distribution and surface activity of macromolecules in offline simulations of marine organic chemistry

“…Two-dimensional acid base relationships and reactive chemistry can also occur along aqueous interfaces (Kanicky and Shah 2002). Electrostatic interactions may enhance the effective thickness of the adsorbed material (Parra-Barraza et al 2005). At least some of these challenges may be susceptible in the near term to a careful blend of theoretical and laboratory investigations.…”

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

“…The latter include the inability to reproduce in vivo conditions for the cell and the use of only a few components of a real cell. Nevertheless, with present technology some types of molecular-level information can only be obtained in membrane models, and therefore several studies have been made with Langmuir monolayers as membrane models [23,[25][26][27][28][29][30][31][32][33].…”