Adsorption properties of BSA and DsRed proteins deposited on thin SiO2 layers: optically non-absorbing versus absorbing proteins.

Protein adsorption on solid surfaces is of interest for many industrial and biomedical applications, where it represents the conditioning step for micro-organism adhesion and biofilm formation. To understand the driving forces of such an interaction we focus in this paper on the investigation of the adsorption of bovine serum albumin (BSA) (optically non-absorbing, model protein) and DsRed (optically absorbing, naturally fluorescent protein) on silica surfaces. Specifically, we propose synthesis of thin protein layers by means of dip coating of the dielectric surface in protein solutions with different concentrations (0.01-5.0 g l-1). We employed spectroscopic ellipsometry as the most suitable and non-destructive technique for evaluation of the protein layers' thickness and optical properties (refractive index and extinction coefficient) after dehydration, using two different optical models, Cauchy for BSA and Lorentz for DsRed. We demonstrate that the thickness, the optical properties and the wettability of the thin protein layers can be finely controlled by proper tuning of the protein concentration in the solution. These results are correlated with the thin layer morphology, investigated by AFM, FTIR and PL analyses. It is shown that the proteins do not undergo denaturation after dehydration on the silica surface. The proteins arrange themselves in a lace-like network for BSA and in a rod-like structure for DsRed to form mono- and multi-layers, due to different mechanisms driving the organization stage.

sP-selectin plasma levels in obesity: association with insulin resistance and related metabolic and prothrombotic factors.

BACKGROUND AND AIM: Soluble P-selectin (sP-sel) represents a marker of platelet activation. This study was addressed to investigate the associations of sP-sel plasma levels with anthropometric parameters, insulin resistance, and related metabolic and prothrombotic factors. METHODS AND RESULTS: 50 non-diabetic women, 17 with normal weight and 33 overweight and obese, aged 18-55 years, were examined. Measurements included body mass index (BMI), central fat accumulation (evaluated by waist circumference), systolic and diastolic blood pressure levels, fasting plasma concentrations of sP-sel, glucose, lipids (triglycerides, total cholesterol and HDL-cholesterol), insulin, and prothrombotic factors (plasminogen activator inhibitor-1, von Willebrand factor, fibrinogen), and insulin resistance (estimated by the homeostasis model assessment: HOMA(IR)). Overweight and obese women had higher fasting plasma sP-sel concentrations compared to normal-weight controls (P<0.05). sP-sel concentrations were positively correlated with BMI, HOMA(IR), systolic and diastolic blood pressure, fasting insulin, triglyceride and PAI-1 plasma levels (P<0.05 for all the correlations). When a multiple regression analysis was performed, with P-sel as dependent variable and all the other parameters as independent variables, P-sel did not maintain a significant relationship with any of these variables. CONCLUSIONS: s-P-selectin plasma concentrations are higher in overweight and obese insulin resistant subjects, thus possibly contributing to the cardiovascular risk of these patients. However, body fatness and insulin resistance are not independent determinants of fasting plasma sP-sel concentrations.