A high throughput method using electron microprobe analysis for quantification of protein adsorption on surfaces

Protein adsorption on solid surfaces can be easily and accurately quantified by electron microprobe analysis using wavelength dispersive spectroscopy (WDS) to detect the carbon and nitrogen atoms within the protein. The method was calibrated by measurements of the carbon and nitrogen WDS signals for sputtered carbon and C_0.72N_0.28 films of known mass per unit area. Fibrinogen adsorption isotherms on silicon wafers and sputtered Ni film samples were studied using this method. The sensitivities for fibrinogen are about 20 ng/cm² using carbon WDS, and about 60 ng/cm² using nitrogen WDS with a circular electron beam of 50 μm diameter. The fibrinogen adsorption results on Si and Ni are in agreement with reported values in the literature. This study suggests that WDS studies are a reliable way to rapidly and automatically screen metallic biomaterials, including combinatorial libraries, in a quantitative manner for their protein affinity.