Kinetics and energetics of plasma protein adsorption onto mineral microparticles

The early events pertaining to protein adsorption and desorption onto various mineral particles were studied employing real time, in situ measurements. The experimental method involved continuous measurements of the outflowing protein concentration with a fluorescence spectrometer, based on the natural fluorescence of the proteins. The acquired data were interpreted, according to a kinetic model, in terms of protein binding rates. From the latter, the kinetic association (k _a) and dissociation (k_d) constants were determined. To avoid the influence of steric hindrance, only data points obtained within the first 0.5 s from the initialization of the experiments were used. Protein concentration effects were found to be pronounced in the determination of the kinetic association constant and less significant in the case of the kinetic dissociation constant. The energy of the non-covalent bonds that are formed between the protein and the surface during adsorption was calculated from the kinetic data. Finally, use of the extended DLVO (XDLVO) theory allowed the calculation of the type of non-covalent bonds, as well as the ratio of favorable to unfavorable protein orientations upon adsorption, also known as von Smoluchowski´s factor, f