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In this paper, the wettability of chitosan/phospholipid (1,2-dipalmitoylsn-glycero-3-phosphocholine - DPPC), chitosan/lipid (cholesterol - Choi) and chitosan/protein (cyclosporine A - CsA) films on air plasma activated polyetheretherketone (PEEK) plates was studied. The layers were prepared using the solution spreading technique and their surface wetting properties were determined based on the measurements of the advancing and receding contact angles of water, formamide and diiodomethane. Moreover, based on the contact angle hysteresis model of Chibowski, values of total surface free energy were estimated. Significant changes in PEEK polarity were observed after plasma activation and modifications with Ch/DPPC, Ch/Chol and Ch/CsA layers. These molecules modulate the chitosan film surface by changing the type and magnitude of interactions, which is revealed in the values of surface free energy'. These results may be important for the development and implementation of highly biocompatible bone substitution polymers coated with chitosan film with antifungal and anti-bactericidal properties. Those systems based on chitosan may also carry and release biologically active substances which could be relevant in the new generation of drug delivery systems. [ABSTRACT FROM AUTHOR]

Solution spreading and Langmuir-Blodgett/Schaefer techniques were used for preparation of chitosan/phospholipid (DPPC) films on air plasma treated polyethylene terephthalate (PET) plates. The surface wetting properties were determined based on the measurements of the advancing and receding contact angles of water, formamide and diiodomethane. The contact angle hysteresis model of Chibowski was applied to estimate the total surface free energy values. The coatings properties were found to be affected by molecular organisation and packing depending on the preparation technique. Phospholipid molecules modified the chitosan film surface by changing the kind and magnitude of interactions, which is revealed in the values of surface free energy. These findings may be helpful for the development of new generation polymer-supported biocompatible coatings with anti-thrombogenic and anti-bactericidal properties, thus expanding the spectrum of chitosan applications. [ABSTRACT FROM AUTHOR]

Abstract: Adsorption of dipalmitoylphosphatidylcholine (DPPC) from NaCl solution on SiO2 particles in suspension was investigated by means of zeta potential and effective diameter measurements as a function of pH using dynamic light scattering. Also, the zeta potential of DPPC aggregates in the same environment was measured. By comprising the results, it was found that DPPC adsorbs on the silica surface, which resulted in decrease of negative zeta potential of the silica suspension. However, DPPC stabilized the SiO2 particle aggregates, which resulted in smaller and smoother changes of the aggregate size during 2h-time experiments, probably due to steric stabilization. In the next series of the experiments the effect of enzymes (phospholipase A2 or lipase Candida Cylindracea) on the behavior of the silica/DPPC suspension was studied. The kind of the enzymes; the hydrolysis products, which were palmitic acid and lysophosphatidylcholine (or glycerylphosphorylcholine), and pH influenced the suspension zeta potential. The lipase was found to be a more active enzyme, both at natural pH=5.8 and pH=8. The evaluated parameters connected with the adsorption process and resulting from enzyme action seem to be helpful for further characterization of the silica/DPPC system, which is discussed in the paper. [Copyright &y& Elsevier]

Abstract: Wetting properties of commercial Al2O3 plates contacted with dipalmitoylphosphatidylcholine (DPPC) or DPPC+enzyme (phospholipase PLA2) in NaCl solution were determined by thin layer wicking and with the help of Washburn equation. Van Oss et al.’s approach to interfacial free energy interactions was applied to determining the solid surface free energy components. Wicking experiments were performed both for bare and alumina plates precontacted overnight with the probe liquid saturated vapours, as well as the untreated and DPPC (or DPPC+PLA2) treated alumina plates. For this purpose the penetration rates of n-octane, water and formamide were measured. From these experiments it resulted that original alumina surface is strongly polar with electron–donor interactions originating from the surface hydroxyl groups. Adsorption of DPPC on Al2O3 plates slightly increased the hydrophobic character of the alumina surface (considerable decrease of the electron–donor, parameter and component was visible) in such a way that the hydrocarbon chains were directed outwards and the polar part towards the alumina surface. However, after the enzyme action the products of DPPC hydrolysis by PLA2 (palmitic acid and lysophosphatidylcholine) increased again the hydrophilic character of Al2O3 surface (a minor increase in component and drastic increase of the electron-donor parameter was noticeable). After treatment with DPPC or DPPC+enzyme PLA2 solution the changes of the total surface free energy of alumina and its Lifshits-van der Waals () component were in the range 7–10mJ/m2, but the most considerable and delivering more interesting information were the changes of the electron–donor () parameter ranging from 27 to 35mJ/m2. Moreover, the changes of the alumina surface wettability were dependent on the time of the enzyme contacting with DPPC in NaCl solution. On the basis of the obtained results it seems that the thin layer wicking method can be an additional useful tool in investigations of the effect of phospholipid and PLA2 action on the hydrophilic–hydrophobic character of alumina surface. [Copyright &y& Elsevier]

Abstract: Adsorption of phospholipid (DPPC) from NaCl electrolyte solution (or from chloroform solution) on Al2O3 particles in suspension was investigated by means of the zeta potential and effective diameter measurements as a function of pH using dynamic light scattering. Al2O3 particles were precovered with an amount of dipalmitoylphosphatidylcholine sufficient to cover the alumina surface by the statistical mono- or bilayer (ML or BL). It was found that DPPC from NaCl solution was adsorbed on Al2O3 surface independently of phospholipid concentration, which resulted in decrease of the initial zeta potential of Al2O3 suspension. When alumina was precovered with DPPC from chloroform (ML or BL) some reorientation of phospholipid molecules could take place. Despite the lowering of the zeta potential value in both cases (from both aqueous and chloroform solution) DPPC stabilized the Al2O3 particle aggregates, which resulted in smaller and smoother changes of the aggregate size during 2-experiment hours due to steric and electrostatic stabilization. In the next series of experiments the effect of enzymes (phospholipase A2 or lipase Candida cylindracea) on the behavior of Al2O3/DPPC particles was studied. The kind of the enzymes, the hydrolysis products, which were palmitic acid and lysophosphatidylcholine (or glycerylphosphorylcholine), and pH changed the suspension zeta potential and influenced the stability of these systems. Lipase was found to be a more active enzyme than phospholipase. The electrokinetic parameters connected with the adsorption process and resulting from the enzyme action seem to be helpful for characterization of the Al2O3/DPPC suspension and the activity of the enzymes, which is discussed in the paper. [ABSTRACT FROM AUTHOR]

Abstract: Wetting properties of silica plates contacted with dipalmitoylphosphatidylcholine (DPPC) or DPPC/enzyme (phospholipase PLA2) in NaCl solution were determined by thin layer wicking and with a help of Washburn equation. The wicking experiments were performed both for bare plates and the silica plates precontacted overnight with the probe liquid saturated vapors the silica plates, as well as untreated and DPPC (or DPPC/enzyme) treated. Adsorption of DPPC on original silica plates increases a bit hydrophobic character of silica surface in such a way that hydrocarbon chains are directed outwards and the polar part towards the silica surface. However, after the enzyme action the products of DPPC hydrolysis by PLA2 (palmitic acid and lysophosphatidylcholine) increase again hydrophilic character of silica surface (an increase in acid–base interactions, ). The changes of silica surface wettability are evidently dependent on the time of enzyme contacting with DPPC in NaCl solution. Although, the changes of total surface free energy of silica after treatment with DPPC/enzyme solution are minor about 2–6mJ/m2, the changes of the electron-donor () and Lifshitz–van der Waals () component of the surface free energy are noticeable. Despite, these results are somehow preliminary, it seems that thin layer wicking method is an interesting tool for investigation of the effect of adsorbed DPPC on hydrophobicity/hydrophilicity of silica surface and influence of enzyme PLA2 action. [Copyright &y& Elsevier]

The aim of the study was to determine the bactericidal properties of popular medical, pharmaceutical, and cosmetic ingredients, namely chitosan (Ch), hyaluronic acid (HA), and titanium dioxide (TiO2). The characteristics presented in this paper are based on the Langmuir monolayer studies of the model biological membranes formed on subphases with these compounds or their mixtures. To prepare the Langmuir film, 1,2-dipalmitoyl-sn-glycero-3-phospho-rac-(1-glycerol) (DPPG) phospholipid, which is the component of most bacterial membranes, as well as biological material-lipids isolated from bacteria Escherichia coli and Staphylococcus aureus were used. The analysis of the surface pressure-mean molecular area (π-A) isotherms, compression modulus as a function of surface pressure, CS−1 = f(π), relative surface pressure as a function of time, π/π0 = f(t), hysteresis loops, as well as structure visualized using a Brewster angle microscope (BAM) shows clearly that Ch, HA, and TiO2 have antibacterial properties. Ch and TiO2 mostly affect S. aureus monolayer structure during compression. They can enhance the permeability of biological membranes leading to the bacteria cell death. In turn, HA has a greater impact on the thickness of E. coli film. [ABSTRACT FROM AUTHOR]