Measurement of interaction forces between fibrinogen coated probes and mica surface with the atomic force microscope: The pH and ionic strength effect

Abstract

The study of protein-surface interactions is of great significance in the design of biomaterials and the evaluation of molecular processes in tissue engineering. The authors have used atomic force microscopy (AFM) to directly measure the force of attraction/adhesion of fibrinogen coated tips to mica surfaces and reveal the effect of the surrounding solution pH and ionic strength on this interaction. Silica colloid spheres were attached to the AFM cantilevers and, after plasma deposition of poly(acrylic acid), fibrinogen molecules were covalently bound on them with the help of the cross-linker 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) in the presence of N-hydroxysulfosuccinimide (sulfo-NHS(. The measurements suggest that fibrinogen adsorption is controlled by the screening of electrostatic repulsion as the salt concentration increases from 15 to 150 mM, whereas at higher ionic strength (500 mM) the hydration forces and the compact molecular conformation become crucial, restricting adsorption. The protein attraction to the surface increases at the isoelectric point of fibrinogen (pH 5.8), compared with the physiological pH. At pH 3.5, apart from fibrinogen attraction to the surface, evidence of fibrinogen conformational changes is observed, as the pH and the ionic strength are set back and forth, and these changes may account for fibrinogen aggregation in the protein solution at this pH.

Distribution of Sialic Acids on Mucins and Gels: A Defense Mechanism

“…To derive the kinetic constants of lectin-sialic acid interactions, we analyzed only force curves that showed single rupture events (i.e., 80% of the total 3120 force curves that contained specific interactions). These would predominantly represent single receptor-ligand unbinding events (40). Following Rinko et al (36), we used the single-barrier Bell and Tees models, and the Bell-Evans paradigm, which models multiple barriers Biophysical Journal 102(1) 176-184 as a series of linear regimes.…”

Challenges in drug delivery to the brain: Nature is against us

“…The influence of different particle properties on protein binding was analyzed in detail by several research groups [1][2][3][10][11][12][13][14][18][19][20]. The initial protein shell of more abundant proteins was found to be substituted by proteins with a higher binding affinity for the NP material.…”

The role of ionic interactions in the adherence of theStaphylococcus epidermidisadhesin SdrF to prosthetic material

“…The cation concentration (ionic strength) of a solution also affects protein–surface interactions. Cations can interfere with the hydrostatic and electrostatic forces that operate in the adsorption of proteins to surfaces (Agnihotri & Siedlecki, ; Tsapikouni et al ., ). Increasing concentrations of several ions (Ca 2+ , Li 1+ , Na 1+ , Mg 2+ ) reduced the attachment bacteria expressing SdrF and the B domain and subunit to polystyrene.…”

“…Infections are among the most common complications of prosthetic device implantation (Baddour et al ., ; Gandelman et al ., ; Wang et al ., ). The capacity of bacteria to adhere to these devices through both specific and nonspecific interactions is a critical first step in the initiation of these infections (Broekhuizen et al ., ; Tsapikouni et al ., ; Otto, ). This problem is enhanced when the infection involves devices such as ventricular assist devices that are critical to patient survival (Rose et al ., ).…”