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Wetting properties of glass surface covered with a bioglass layer in the hyaluronic acid (HA), alginate (AL) or mixed solution were determined from the contact angle measurements by the sessile drop method. Air plasma modification of plates to increase adhesion was performed in the low-temperature plasma system. Adhesion of bioglass in the polysaccharide solution on the original glass plates usually increases hydrophobic character of glass surface insignificantly in such a way that hydrocarbon chains are directed outwards and the polar part towards the glass surface. However, after the plasma action hydrophilic character of glass (and glass with biological layer) surface increases again. The changes of glass surface wettability are evidently dependent on the kind of used probe liquid and concentration of bioglass in the polysaccharide solution. Using an optical profilometer, the surface roughness of the plates was determined. An effective smoothing of the bioglass/polysaccharide surface was obtained on the plasma treated surface. The correlation between the hysteresis of water (and/or simulated body fluid) wetting angles and the topography of the surface was found for such mixed systems. However these results are somehow preliminary, it seems that cold plasma modification is an interesting tool for the development of the effect of bioglass adhesion and change of hydrophobicity/hydrophilicity character of glass materials in order to increase the spectrum of its pharmaceutical application. [ABSTRACT FROM AUTHOR]

In our studies the hybrid chitosan/1,2-dipalmitoyl- sn -glycero-3-phosphocholine (Ch/DPPC) films on the air plasma treated polyethylene terephthalate (PET) plates were prepared using a few methods: spreading (S), Langmuir–Blodgett (LB) and Langmuir–Schaefer (LS). Wetting properties of the prepared layers were determined measuring the contact angles of water, formamide and diiodomethane. Moreover, the theoretical model proposed by van Oss et al. was used to study the surface thermodynamics, i.e. surface free energy and its components. The surface topography was analyzed based on the images from atomic force microscope (AFM), optical and mechanical profilometers. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used for surface chemical analysis. It was found that the way of layers preparation had a significant effect on wetting properties and surface free energy of the PET/Ch/DPPC films. Both topographic features and surface chemistry influenced the material characteristics. Moreover, the study gives information on the film polarity strongly affected by the molecular organization and packing. It is believed that the DPPC molecules, modifying the chitosan coating, can improve its hemostatic properties to obtain a positive assessment of athrombogenicity. Therefore the developed surfaces seem to be promising for the enhanced PET biocompatibility suitable for cardiovascular devices. [ABSTRACT FROM AUTHOR]

The main goal of this paper was to determine interfacial properties of base untreated PET (polyethylene terephthalate) and starch modified PET as a function of time of air plasma processing. Air plasma was applied to improve the interfacial adhesion of starch to PET as an effect of oxidation and cross-linking changes. In turn, starch was used because the poor oxygen permeability of its layer can have a potential for the preservation of numerous food and pharmaceutical products. Wettability of the surfaces and work of adhesion on the basis of measurements of advancing and receding contact angles for the probe liquids on the PET plates base and covered with a starch film were obtained. The short plasma treatment was immediately followed by a sharp decrease of contact angle. Largely, in the course of longer plasma acting the contact angle of all liquids slightly increases due to the reorientation of polar groups towards the surface layer of polymer. Moreover, thermal and mechanical properties of base PET and those modified with air plasma were determined. Significant differences in elongation at break, but small differences in thermal stability and flexural properties of PET after plasma modification were observed. The starch film surface was characterized by FTIR measurements which confirm the contact angle results. Changes of time of plasma treatment and/or starch modification combination led to improvement of PET interfacial properties and biocompatibility. The obtained results expand the characteristics of PET/starch materials, which is of significant importance, particularly to formulate new starch coatings with controlled release and new biocompatible packaging PET/starch films with special properties. [ABSTRACT FROM AUTHOR]

In our studies the low-temperature plasma obtained from oxygen, argon, nitrogen was used to enhance polyetheretherketone PEEK adhesive properties and as “pre-deposition” before the main process which was deposition of layers of biologically active substances, e.g. phospholipid 1,2-dipalmitoyl- sn -glycero-3-phosphocholine (DPPC), lauryl gallate (LG) and mixed layers (DPPC/LG) by means of the Langmuir-Blodgett technique. Thus PEEK was used for creating biointerfaces with model membrane structures. Wettability of both unmodified and modified surfaces of the polymer as well as those covered with the films of biological substances was investigated by measurements of advancing and receding contact angles of water, formamide and diiodomethane. Then the values of the measured contact angles were used for determination of surface free energy and its components of the studied surfaces based on the theoretical models. The topography and roughness parameters were also estimated by optical profilometer. The results demonstrate that the appropriate plasma choice and the deposited film composition influence on wettability and thermodynamic parameters of the studied systems. The changes in the PEEK surface properties affect the interactions between the solid support and the membrane. The molecular packing density of the deposited film can be associated with the strength of adhesion and correlates with the surface energy and its component values. It is believed that plasma treatment will be a source of new information about PEEK surface mostly in the field of biomaterial engineering, adhesion of biomolecules as well as biocompatibility. [ABSTRACT FROM AUTHOR]

The objective of this work was to determine surface properties of biopolymer film as a function of temperature and/or after plasma treatment with the aim of further wettability tests and biocompatibility. The examined biopolymers were native starch and starch modified by solution of PC (phosphatidylcholine). Contact angles for polar water (and formamide) and nonpolar diiodomethane on the glass plates covered with starch film before and after gelatinization (25 °C, 37 °C and 60 °C) were measured for the base and plasma modified film. The surface free energy of solid (gel) was determined from the advancing and receding contact angles of these probe liquids, using the contact angle hysteresis model (CAH). The plasma treatment was immediately followed by a sharp decrease of contact angle and in the course of ageing the contact angle also decreased due to the reorientation of polar groups into the polymer surface layer. To depict better changes in hydrophilic/hydrophobic character of the starch surface before and after modification the work of water spreading, W S was calculated. A sharp decrease in negative values of W S takes place which indicates more hydrophilic character of starch surface after modification. Surface morphology and roughness were studied by optical profilometer and FTIR measurements which confirm the contact angle results. It was also proved that a combination of input treatment parameters led to improvement of biopolymer wettability and provided possibilities of starch application where uniform thin films are required. [ABSTRACT FROM AUTHOR]

Abstract: The electrokinetic properties of n-tetradecane/ethanol emulsions in the presence of dipalmitoylphosphatidylcholine (DPPC) and enzyme (lipase Candida cylindracea or phospholipase A2) were investigated. Applying the dynamic light scattering zeta potentials and effective diameters of the emulsions droplets were determined as a function of pH and enzyme concentration. Investigation of the electrokinetic phenomena in the presence of phospholipids and enzymes are important for better understanding processes occurring in biological and pharmaceutical systems at interfaces like solid surfaces, cell membranes and oil–water interfaces. Generally, it was found that the presence of DPPC molecules decrease the negative zeta potentials of n-tetradecane droplets and the charge repulsion. Lipase presence increases the negative zeta potentials of n-tetradecane/DPPC (in ethanol) droplets at acidic and natural pH. In the buffer (pH 8) and pH 12 small decrease in the negative zeta potential of n-tetradecane/DPPC droplets is visible. On the other hand if PLA2 enzyme is used small increase in the negative zeta potential of n-tetradecane/DPPC (in buffer) droplets occurs. It is believed that the differences in the enzyme effect on the measured parameters result from hydrolysis reaction and preferable pH of catalytic reaction. Possible reasons for the observed changes of zeta potential and effective diameter are discussed. [Copyright &y& Elsevier]

Abstract: Extensive investigations of electrokinetic properties of emulsions and suspensions deal among other things with the application of natural stabilizers. Dipalmitoylphosphatidylcholine (DPPC) is present in many biochemical processes including living organisms. In this paper the dynamic properties of n-tetradecane/water emulsions were studied in the presence of DPPC which changes the interfacial free energy and the zeta potential. The zeta potential of the emulsion was determined as a function of pH and electrolyte concentration. H+/OH− ions were found to determine the potential, and also a clearly visible effect of the Na+, Ca2+ and La3+ ions appeared. The decrease in absolute value of the zeta potential was usually accompanied by a growth in effective diameter of the emulsion droplets. To better describe the stabilizing mechanism of DPPC, the electric charge at the shear plane was calculated using the zeta potentials and diameters of the droplets, assuming spherical particles. In n-tetradecane/electrolyte emulsion stabilized by DPPC the zeta potential may be also related to acid–base interactions. From the results, however, repulsion of double layers was concluded to be the main stabilizing mechanism. Possible stabilizing effect of DPPC liposomes and/or other aggregates with adsorbed ions needs further investigations. [Copyright &y& Elsevier]

Abstract: Properties of surface of hydrophobic liquid (e.g. n-alkane) in aqueous solutions are very important for stability of dispersed systems, i.e. emulsions and suspensions, as well as in many biochemical processes including living organisms. Application of natural stabilizers it is a key aspect of wide-ranging investigations of emulsion. One of such systems is oil/lecithin solution. The adsorbed lecithin layer at the oil droplets determines the structural and dynamic properties of oil/water emulsions. It changes the interfacial free energy and the zeta potential. The zeta potentials determined in this paper as a function of time and pH confirm that H+/OH− ions are potential determining and the largest effect of OH− is visible at alkaline pHs. The decrease in absolute value of the zeta potential was accompanied by a growth in the effective diameter of emulsion droplets. Using both the potential and diameters electric charge at the shear plane for spherical particle was calculated. In these systems the zeta potential may be created by immobilized and oriented water dipoles and acid–base interactions. However, on the basis of the results it is concluded that the main stabilizing mechanism is the double layers repulsion, besides possible stabilizing effect of lecithin liposomes and other aggregates. [Copyright &y& Elsevier]

The Langmuir technique allows for the characterization of monolayers of biological and/or biologically active compounds which have high potential for application in tissue engineering to improve the implants biocompatibility. This group of substances includes 1,2-dioleoyl- sn -glycero-3-phosphocholine (DOPC), cyclosporine A (CsA), lauryl gallate (LG), and chitosan (Ch). The single (DOPC, CsA, LG), binary (DOPC-CsA 1:1) and ternary (DOPC-CsA-LG 3:3:2, 1:1:2, 1:1:6 that correspond to χ LG = 0.25, 0.50, 0.75) monolayers on the acidic subphase with or without chitosan (Ch) were characterized using the Langmuir technique coupled with the surface potential meter. The dependence of the surface pressure and the surface potential on the area per molecule (π − A and ∆ V − A isotherms, respectively) was determined. Based on the above isotherms data, the compression modulus (C s − 1), excess and total Gibbs energy of mixing (∆ G exc and ∆ G mix) as well as the apparent dipole moment (μ a) were calculated. These parameters allowed drawing conclusions about the molecular packing, the orientation of molecules, the type and magnitude of interactions within the monolayers, and finally about their stability, depending on the components proportions and the contribution of Ch molecules. The main findings indicated that the insertion of LG to the binary DOPC-CsA 0.50 monolayer resulted in a shift of the π − A isotherms towards smaller areas per molecule, the smaller areas the higher amount of LG. That correlated with an increase in packing density (larger C s − 1 values) and an attraction between the molecules (revealed by the negative ∆ G exc and ∆ G mix values) in the three-component monolayers. Furthermore, the addition of chitosan (Ch) molecules into the subphase stiffened the multicomponent (DOPC-CsA or DOPC-CsA-LG) films. The strengthening of the attractive interactions and better miscibility were observed for all the DOPC-CsA-LG films. Therefore, these monolayers spread on the Ch subphase were found to be thermodynamically stable (among them the most stable was DOPC-CsA-LG 0.50) and could be successfully used for coating implants in order to improve their biocompatibility with the surrounding tissues. [Display omitted] • Chitosan (Ch) molecules enhance the attraction between the DOPC, CsA and LG molecules. • Presence of Ch increases the surface potential and the apparent dipole moment values. • Ternary DOPC-CsA-LG monolayers on the Ch subphase are thermodynamically stable. • Obtained monolayers can be transferred to a solid support to improve its biocompatibility. [ABSTRACT FROM AUTHOR]

The study aimed to determine the chemical nature, energy state, and topography of chitosan and/or TiO 2 thin layers, which were transferred from different aqueous solutions or dispersions onto a solid support (mica) by a dip-coating method using the Langmuir-Blodgett trough. The surface topography was analysed using an optical profilometer. The performed wettability measurements were used to estimate changes in the total surface free energy based on the theoretical mathematical Lifshitz-van der Waals-Acid-Base model. In addition, the Langmuir technique was employed to determine the effect of Ch-TiO 2 and/or hyaluronic acid (HA) on the model membrane properties in aspect of biocompatibility. The prepared materials can be classified as high-energy, hydrophilic, with roughness in the nanometric scale. Physicochemical parameters have a significant impact on the processes that take place in the surface layer of the biomaterial being in contact with the biological environment. [Display omitted] • Biocompatible chitosan-TiO 2 coating with nano-scale irregularities was obtained on mica. • Surface properties of novel material (Ch-HA-TiO 2) were characterized. • Relationship between wettability and surface microstructure was shown. • Hybrid biomaterial exhibited the high surface free energy. • Presence of the hyaluronic acid increased the biocompatibility of Ch-TiO 2 combination. [ABSTRACT FROM AUTHOR]