Interactions of nanoparticles with body proteins--improvement of 2D-PAGE-analysis by internal standard

Two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) is the method of choice to investigate protein adsorption of blood proteins (opsonization) onto nanoparticular drug carriers. In general the reproducibility of the obtained adsorption patterns is satisfying. However, direct comparison between the amounts of single protein spots from gels obtained in different runs is difficult, because 2D-PAGE is a multistep procedure. A possible solution of the problem is to establish a protein as internal standard. Therefore, selected proteins (Bio-rad) were under investigation. Due to its molecular weight and isoelectric point, soybean trypsin inhibitor (TI) does not interfere with plasma components. Therefore, a method was established to use TI as an internal standard protein to improve comparability between the 2D-PAGE gels obtained in different analytical runs.