Cell membrane microfragments called microvesicles (MV) originating from different cells are circulating in the blood of healthy subjects and their elevated numbers are found in different diseases, including cancer. This study was designed to characterise MV present in plasma of gastric cancer patients. Since majority of MV in blood are platelets-derived (PMV), plasma samples deprived of PMV were used. In comparison to control, the number of MV in patients was significantly elevated in all stages, higher in more advanced disease. Patients' MV showed an increased membrane expression of CCR6 and HER-2/neu. The proportion of MV carrying some leucocyte determinants was low and similar in patients and control. Transmission electron microscopy showed their substantial heterogeneity in size and shape. The size determined by dynamic light scattering analysis confirmed this heterogeneity. The MV size distribution in patients was broader within the range of 10-800 nm, while in control MV showed 3-mode distribution within the range of 10-400 nm. Atomic force microscopy confirmed MV size heterogeneity with implication that larger objects represented aggregates of smaller microparticles. Patients' MV exhibited increased absolute values of zeta potential, indicating a higher surface charge. Tumour markers HER-2/neu, MAGE-1, c-MET and EMMPRIN were detected both in control and patients' samples with stronger expression in the latter. Significantly higher expression of MAGE-1 and HER-2/neu mRNA was observed in individual patients. All together, it suggests that at least some MV in plasma of gastric cancer patients are tumour-derived. However, their role in cancer requires further studies.

Adsorption of fibrinogen, modeled as a linear chain of touching beads of various sizes, was theoretically studied using the random sequential adsorption (RSA) model. The adsorption process was assumed to consist of two steps: (i) formation of an irreversibly bound fibrinogen monolayer under the side-on orientation, which is independent of the bulk protein concentration and (ii) formation of the reversibly bound, end-on monolayer, whose coverage was dependent on the bulk concentration. Calculation based on the RSA model showed that the maximum surface concentration of the end-on (reversible) monolayer equals N(⊥∞) = 6.13 × 10(3) μm(-2) which is much larger than the previously found value for the side-on (irreversible) monolayer, equal to N(∞) = 2.27 × 10(3) μm(-2). Hence, the maximum surface concentration of fibrinogen in both orientations is determined to be 8.40 × 10(3) μm(-2) corresponding to the protein coverage of 5.70 mg m(-2) assuming 20% hydration. Additionally, the surface blocking function (ASF) was determined for the end-on fibrinogen adsorption, approximated for the entire range of coverage by the interpolating polynomial. For the coverage approaching the jamming limit, the surface blocking function (ASF) was shown to vanish proportionally to (θ(⊥∞) - θ(⊥))(2). These calculation allowed one to theoretically predict adsorption isotherms for the end-on regime of fibrinogen and adsorption kinetics under various transport conditions (diffusion and convection). Using these theoretical results, a quantitative interpretation of experimental data obtained by TIRF and ellipsometry was successfully performed. The equilibrium adsorption constant for the end-on adsorption regime was found to be 8.04 × 10(-3) m. On the basis of this value, the depth of the adsorption energy minimum, equal to -17.4 kT, was predicted, which corresponds to ΔG = -41.8 kJ mol(-1). This is in accordance with adsorption energy derived as the sum of the van der Waals and electrostatic interactions. Besides having significance for predicting fibrinogen adsorption, theoretical results derived in this work also have implications for basic science providing information on mechanisms of anisotropic protein molecule adsorption on heterogeneous surfaces.

Irreversible side-on adsorption of fibrinogen, modeled as a linear chain of touching beads of various size, was studied theoretically using the random sequential adsorption (RSA) model. Numerical simulation of the Monte Carlo type enabled one to determine the dependence of the surface blocking function (available surface function) on the protein coverage. These numerical results were interpolated using analytical functions based on a polynomial expansion. The dependence of the jamming coverage on the size of the simulation area was also determined. By an extrapolation of these results to the infinite area size, the maximum surface concentration of fibrinogen for the side-on adsorption was determined to be 2.26 Â 10 3 μm -2 . This corresponds to a jamming coverage θ ¥ of 0.29. It was shown that the blocking function can well be approximated in the limit of high coverage by the dependence C(θ ¥ -θ) 4 . Using this interpolating expression, the kinetics of fibrinogen adsorption under convection and diffusion transport conditions were evaluated for various bulk concentrations of the protein. These kinetic curves were derived by numerically solving the mass transport equation in the bulk with the blocking function used as a nonlinear boundary condition at the interface. It was shown that our theoretical results are in agreement with experimental kinetic data obtained by AFM, ellipsometry, and other techniques for hydrophilic surfaces in the limit of low bulk fibrinogen concentration.

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Adsorption of fibrinogen was theoretically studied using the three-dimensional random sequential adsorption (RSA) model. Fibrinogen molecule shape was approximated by the bead model considering the presence of flexible side arms. Various cases were considered inter alia, the side-on adsorption mechanisms and the simultaneous side-on/end-on adsorption mechanism. The latter mechanisms is pertinent to fibrinogen adsorption at lower pH (below isoelectric point of 5.8) where the entire molecule is positively charged. Extensive calculations enabled one to determine the jamming surface concentration (coverage) of molecules adsorbed under the side-on and end-on orientations as well as the total coverage. For the simultaneous side-on/end-on model the maximum surface concentration was 7.29 × 10(3) μm(-2) corresponding to the protein coverage of 4.12 mg m(-2) (without considering hydration). Additionally, the surface blocking functions for different adsorption regimes were determined and analytically approximated for the entire range of coverage by the interpolating polynomials. Using these blocking functions, fibrinogen adsorption kinetics for diffusion controlled transport conditions was evaluated. Comparison of these theoretical results with experimental data was made. It was demonstrated that the simultaneous side-on/end-on model properly reflects the maximum coverage of fibrinogen adsorbed on latex particles determined via the electrokinetic (electrophoretic mobility) and AFM measurements. Also, streaming potential measurements of fibrinogen adsorption kinetics on mica were successfully interpreted in terms of this model. The theoretical results derived in this work have implications for basic science providing information on mechanisms of anisotropic protein adsorption.

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The first theoretical study of a dimers adsorption process at homogeneous surface is presented. By using the RSA algorithm, we show example monolayers, discuss estimations of random jamming coverage and measure the surface blocking function, which could be used for calculating real systems kinetics. We also found the correlation function for generated coverages and analysed orientational ordering inside the adsorbed monolayer. Results were compared with theoretical and experimental data.

Monodisperse silver nanoparticle sols were synthesized via chemical reduction processes in aqueous environment without using polymeric stabilizing agents or surfactants. The sols obtained using various reducing agents; inorganic cell permeabilizers and organic phenolic compounds; inter alia gallic acid (GA) and tannin (TA) were thoroughly characterized by various physicochemical methods such as TEM, SEM, AFM, DLS and micro-electrophoresis. The antibacterial activity of the sols against two E. coli strains was characterized via the determination of the Minimum Bactericidal Concentration (MBC). All sols exhibited a pronounced bactericidal effect against the standard K12 strain, especially the GA and TA sols showing MBC concentration as low as 1-5 mg L(-1). In the case of the antibiotic resistant strain the highest activity (MBC of 10 mg L(-1)) was observed for the sol synthesized using sodium hypophosphate and sodium tripolyphosphate. Additionally, interactions of silver nanoparticles with bacteria cell were studied using TEM and AFM imaging. It was shown that the silver particles attach to the bacteria surface inducing disintegration, which enables their penetration inside the bacteria. Our measurements confirmed that the surface chemistry of silver nanoparticles can play a decisive role.