Self-consistent field model of inhomogeneous adsorption of nonionic surfactants onto polystyrene latex

The structure of a nonionic surfactant layer adsorbed on a hydrophobic surface is studied by means of a molecular realistic self-consistent field theory. The formation of discrete surface aggregates is considered. Combining the one-gradient self-consistent field theory with the two-gradient one, which allows for lateral inhomogeneities in the adsorbed layer, we predict the adsorption isotherm and the surface structure for surfactants with a branched hydrocarbon tail and several lengths of the PEO head. Analyzing the surface free energy of the system, it is found that the structure of the adsorbed layer changes along the isotherm. At very low surfactant concentrations a homogeneous dilute "gas"-like layer of individual surfactants is formed. Above a certain value (still below the cmc) hemispherical aggregates develop on the surface, coexisting with the "gas"-like homogeneous layer. A method is suggested to take interaggregate interactions into account. For the short-headed surfactant, hemicylindrical aggregates appear at higher concentrations. Finally, near the cmc the homogeneous adsorbed layer is recovered. Theoretical adsorption isotherms are compared to the experimental ones for Triton X-100 and Triton X-405 onto a polystyrene Latex dispersion. The model that includes the inhomogeneous adsorption (two-gradient SCF) is significantly closer to the experimental results than the one-gradient SCF theory that has the lateral homogeneous layer as a constraint

Modeling the effect of structural details of nonionic surfactant on micellization in solution and adsorption onto hydrophobic surfaces

Applying the classical one-gradient self-consistent-field (SCF) theory for adsorption and/or association, we can show that the molecular architecture of nonionic surfactants influences strongly the micellization in solution and the adsorption on solid-liquid interfaces. This is illustrated by using two models for the molecule with the same overall structure, one with a linear and one with a more realistic branched hydrocarbon tail. The critical micelle concentration is computed for several lengths of the poly(oxyethylene) headgroup. In addition, the adsorption isotherms of these small surfactants on hydrophobic surfaces were studied. Theoretical results are critically compared to the experimental results for critical micelle concentrations and adsorption isotherms of Triton X-100 and Triton X-405 onto a polystyrene latex dispersion. From this comparison, it was concluded that a SCF model in which homogeneous adsorbed layers are preassumed fails to reproduce experimental findings. It is speculated that lateral inhomogeneities must. be included in the SCF model to improve its performance

Physicochemical characterization of chitosan nanoparticles: electrokinetic and stability behavior

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HCV eradication with IFN-based therapy does not completely restore gene expression in PBMCs from HIV/HCV-coinfected patients

Altres ajuts: Fondo Europeo de Desarrollo Regional (FEDER).Objective: To evaluate the impact of hepatitis C virus (HCV) elimination via interferon (IFN)-based therapy on gene expression profiles related to the immune system in HIV/HCV-coinfected patients. Methods: We conducted a prospective study in 28 HIV/HCV-coinfected patients receiving IFN-based therapy at baseline (HIV/HCV-b) and week 24 after sustained virological response (HIV/HCV-f). Twenty-seven HIV-monoinfected patients (HIV-mono) were included as a control. RNA-seq analysis was performed on peripheral blood mononuclear cells (PBMCs). Genes with a fold-change (FC) ≥ 1.5 (in either direction) and false discovery rate (FDR) ≤ 0.05 were identified as significantly differentially expressed (SDE). Results: HIV/HCV-b showed six SDE genes compared to HIV-mono group, but no significantly enriched pathways were observed. For HIV/HCV-f vs. HIV/HCV-b, we found 58 SDE genes, 34 upregulated and 24 downregulated in the HIV/HCV-f group. Of these, the most overexpressed were CXCL2, PDCD6IP, ATP5B, IGSF9, RAB26, and CSRNP1, and the most downregulated were IFI44 and IFI44L. These 58 SDE genes revealed two significantly enriched pathways (FDR < 0.05), one linked to Epstein-Barr virus infection and another related to p53 signaling. For HIV/HCV-f vs. HIV-mono group, we found 44 SDE genes that revealed 31 enriched pathways (FDR < 0.05) related to inflammation, cancer/cell cycle alteration, viral and bacterial infection, and comorbidities associated with HIV/HCV-coinfection. Five genes were overrepresented in most pathways (JUN, NFKBIA, PIK3R2, CDC42, and STAT3). Conclusion: HIV/HCV-coinfected patients who eradicated hepatitis C with IFN-based therapy showed profound gene expression changes after achieving sustained virological response. The altered pathways were related to inflammation and liver-related complications, such as non-alcoholic fatty liver disease and hepatocellular carcinoma, underscoring the need for active surveillance for these patients