Interaction of algal polysaccharide with lipid Langmuir monolayers

Interactions of Microorganisms with Lipid Langmuir Layers

Preventing microbial contamination of aquatic environments is crucial for the proper supply of drinking water. Hence, understanding the interactions that govern bacterial and virus adsorption to surfaces is crucial to prevent infection transmittance. Here, we describe a new approach for studying the organization and interactions of various microorganisms, namely, Escherichia coli (E. coli) bacteria, E. coli-specific bacteriophage T4, and plant cucumber green mottle mosaic viruses (CGMMV), at the air/water interface using the Langmuir-Blodgett (LB) technique. CGMMV were found as applicable candidates for further studying their interactions with Langmuir lipid monolayers. The zwitterionic, positively, and negatively charged LB lipid monolayers with adsorbed viruses were deposited onto solid supports and characterized by atomic force microscopy. Using polymerase chain reaction, we indicated that the adsorption of CGMMV onto the LB monolayer is a result of electrostatic interactions. These insights are useful in engineering membrane filters that prevent biofouling for efficient purification systems.

Studies on the interfacial behavior of DPPC/DPPG mixed monolayers in the presence of fluoxetine

In this study, the interfacial behavior of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine/1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DPPC/DPPG) mixed monolayers with fluoxetine (FLX) in the subphase was investigated by a combination of the Langmuir-Blodgett technique and atomic force microscopy (AFM). It was found that DPPC/DPPG mixed monolayers showed different interfacial behaviors before and after addition of FLX in the subphase. The electrostatic interaction between FLX and lipids molecules destroys the homogeneity of the mixed monolayers and changes the arrangement of lipids molecules at the interface after addition of FLX in the subphase, thereby leading to an increase of compressibility and miscibility and a decrease in the stability of the mixed monolayers. The surface morphology of the mixed monolayers observed by AFM was different between without and with FLX in the subphase, indicating the penetration of FLX into the mixed monolayers. The present study has provided detailed information for further understanding the interactions of drugs with membrane lipids in other lipid monolayers.

Interaction of Silver-Lignin Nanoparticles With Mammalian Mimetic Membranes

Silver nanoparticles (AgNPs) have broad spectrum antibacterial activity, but their toxicity to human cells has raised concerns related to their use as disinfectants or coatings of medically relevant surfaces. To address this issue, NPs comprising intrinsically bactericidal and biocompatible biopolymer and Ag with high antibacterial efficacy against common pathogens and compatibility to human cells have been engineered. However, the reason for their lower toxicity compared to AgNPs has not yet been elucidated. This work studies the in vitro interaction of AgLNPs with model mammalian membranes through two approaches: (i) Langmuir films and (ii) supported planar bilayers studied by quartz crystal microbalance and atomic force spectroscopy. These approaches elucidate the interactions of AgLNPs with the model membranes indicating a prominent effect of the bioresourced lignin to facilitate the binding of AgLNPs to the mammalian membrane, without penetrating through it. This study opens a new avenue for engineering of hybrid antimicrobial biopolymer – Ag or other metal NPs with improved bactericidal effect whereas maintaining good biocompatibility.

Carbon Nanotubes and Algal Polysaccharides To Enhance the Enzymatic Properties of Urease in Lipid Langmuir-Blodgett Films

Algal polysaccharides (extracellular polysaccharides) and carbon nanotubes (CNTs) were adsorbed on dioctadecyldimethylammonium bromide Langmuir monolayers to serve as a matrix for the incorporation of urease. The physicochemical properties of the supramolecular system as a monolayer at the air-water interface were investigated by surface pressure-area isotherms, surface potential-area isotherms, interfacial shear rheology, vibrational spectroscopy, and Brewster angle microscopy. The floating monolayers were transferred to hydrophilic solid supports, quartz, mica, or capacitive electrolyte-insulator-semiconductor (EIS) devices, through the Langmuir-Blodgett (LB) technique, forming mixed films, which were investigated by quartz crystal microbalance, fluorescence spectroscopy, and field emission gun scanning electron microscopy. The enzyme activity was studied with UV-vis spectroscopy, and the feasibility of the thin film as a urea sensor was essayed in an EIS sensor device. The presence of CNT in the enzyme-lipid LB film not only tuned the catalytic activity of urease but also helped to conserve its enzyme activity. Viability as a urease sensor was demonstrated with capacitance-voltage and constant capacitance measurements, exhibiting regular and distinctive output signals over all concentrations used in this work. These results are related to the synergism between the compounds on the active layer, leading to a surface morphology that allowed fast analyte diffusion owing to an adequate molecular accommodation, which also preserved the urease activity. This work demonstrates the feasibility of employing LB films composed of lipids, CNT, algal polysaccharides, and enzymes as EIS devices for biosensing applications.

Effect of Laminaria japonica polysaccharides on lipids monolayers at the air-water surface

In this paper, we examined the effect of Laminaria japonica polysaccharides (LJP) on cationic 1,2-Dioleoyl-3-Trimethylammonium-Propane (DOTAP) and anionic 1,2-dipalmitoyl-sn-glycero-3-[phospho-rac-1-glycerol] (DPPG) monolayers at the air-water interface by the pressure-area isotherms (π-A), adsorption curves (π-t) and morphology measurements with atomic force microscopy (AFM) technique. The π-A curves revealed that the isotherms shifted to larger mean molecular area with progressive addition of LJP into subphase for both DOTAP and DPPG monolayers. And the compression modulus Cs-1 obtained from π-A curves showed that the elasticity of the films decreased with the addition of LJP. Adsorption curves were measured at the surface pressure of 10 and 20mN/m, which were fitted by the adsorption kinetics equation. It revealed that DOTAP monolayer changed into a mixed film with the insertion of polysaccharides molecules. However, there was no significant effect on the surface pressure for DPPG monolayer. Besides, surface morphology was observed by AFM, which was consistent with the results of fitted adsorption curves.

Chondroitin sulfate interacts mainly with headgroups in phospholipid monolayers

Sulfated glycosaminoglycans are precursors of the extracellular matrix used to treat diseases related to blood clotting and degenerative joint diseases. These medical applications have been well established, but the mode of action at the molecular level, which depends on the interaction with cell membranes, is not known in detail. In this study, we investigated the interaction between chondroitin sulfate (CS) and phospholipid monolayers that mimic cell membranes. From surface pressure isotherms and polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS), CS was found to interact mainly with the polar groups of dipalmitoyl phosphatidylcholine (DPPC) and dipalmitoyl phosphatidylglycerol (DPPG), with negligible penetration into the hydrophobic tails and only small changes in monolayer elasticity for the packing corresponding to a real cell membrane. The changes in surface pressure and surface potential isotherms depended on CS concentration and on the time allowed for its adsorption onto the monolayer, which points to a dynamic adsorption-desorption process. The charge of the phospholipid was also relevant, since CS induced order into DPPC monolayers while the opposite occurred for DPPG, according to the PM-IRRAS spectra. In summary, interaction with polar groups is responsible for the CS effects on model cell membranes.