Adsorption of fibrinogen onto macroporous, biocompatible sponges based on poly(2-hydroxyethyl methacrylate)

Kinetics and isotherm of fibronectin adsorption to three-dimensional porous chitosan scaffolds explored by ¹²⁵I-radiolabelling

In this study, (125)I-radiolabelling was explored to follow the kinetics and isotherm of fibronectin (FN) adsorption to porous polymeric scaffolds, as well as to assess the elution and exchangeability of pre-adsorbed FN following incubation in serum-containing culture medium. Chitosan (CH) porous scaffolds with two different degrees of acetylation (DA 4% and 15%) were incubated in FN solutions with concentrations ranging from 5 to 50 µg/mL. The kinetic and isotherm of FN adsorption to CH were successfully followed using (125)I-FN as a tracer molecule. While on DA 4% the levels of adsorbed FN increased linearly with FN solution concentration, on DA 15% a saturation plateau was attained, and FN adsorbed amounts were significantly lower. These findings were supported by immunofluorescent studies that revealed, for the same FN solution concentration, higher levels of exposed cell-binding domains on DA 4% as compared with DA 15%. Following incubation in serum containing medium, DA 4% also revealed higher ability to exchange pre-adsorbed FN by new FN molecules from serum than DA 15%. In accordance, when assessing the efficacy of passively adsorbed FN to promote endothelial cell (EC) adhesion to CH, ECs were found to adhere at higher levels to DA 4% as compared with DA 15%, 5 µg/mL of FN being already efficient in promoting cell adhesion and cytoskeletal organization on CH with DA 4%. Taken together the results show that protein radiolabelling can be used as an effective tool to study protein adsorption to porous polymeric scaffolds, both from single and complex protein solutions.

PM-IRRAS Investigation of the Interaction of Serum Albumin and Fibrinogen with a Biomedical-Grade Stainless Steel 316LVM Surface

Polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) was applied to investigate the interaction of bovine serum albumin (BSA) and fibrinogen with a biomedical-grade 316LVM stainless steel surface, in terms of the adsorption thermodynamics and adsorption-induced secondary structure changes of the proteins. Highly negative apparent Gibbs energy of adsorption values revealed a spontaneous adsorption of both proteins onto the surface, accompanied by significant changes in their secondary structure. It was determined that, at saturated surface coverages, lateral interactions between the adsorbed BSA molecules induced rather extensive secondary structure changes. Fibrinogen's two coiled coils appeared to undergo negligible secondary structure changes upon adsorption of the protein, while large structural rearrangements of the protein's globular domains occurred upon adsorption. The secondary structure of adsorbed fibrinogen was not influenced by lateral interactions between the adsorbed fibrinogen molecules. PM-IRRAS was deemed to be viable for investigating protein adsorption and for obtaining information on adsorption-induced changes in their secondary structures.