Characterization of the binding sites of the anticancer ruthenium(III) complexes KP1019 and KP1339 on human serum albumin via competition studies

Indazolium trans-[tetrachloridobis(1H-indazole)ruthenate(III)] (KP1019) and its Na+ analogue (KP1339) are two of the most prominent non-platinum antitumor metal complexes currently undergoing clinical trials. After intravenous administration, they are known to bind to human serum albumin (HSA) in a noncovalent manner. To elucidate their HSA binding sites, displacement reactions with the established site markers warfarin and dansylglycine as well as bilirubin were monitored by spectrofluorimetry, ultrafiltration-UV-vis spectrophotometry, and/or capillary zone electrophoresis. Conditional stability constants for the binding of KP1019 and KP1339 to sites I and II of HSA were determined, indicating that both Ru(III) compounds bind to both sites with moderately strong affinity (log K (1)' = 5.3-5.8). No preference for either binding site was found, and similar results were obtained for both metal complexes, demonstrating low influence of the counter ion on the binding event

Analytical Methods for Characterizing the Nanoparticle–Protein Corona

When nanoparticles (NPs) enter a biological environment, medium components, especially proteins, compete for binding to the NP's surface, leading to development of a new interface, commonly referred to as the "protein corona." This rich protein shell gives the NPs a biological identity that can be very different from their synthetic one, in terms of their chemical-physical properties. Understanding NP-protein interaction is crucial for both the bioapplications and safety of nanomaterials. The protein corona provides the primary contact to the cells and their receptors. It defines in vivo fate of the delivery systems, governing the stability, immunogenicity, circulation, clearance rates and organ biodistribution of the NPs. Given its importance, the application and the development of analytical methods to investigate the protein corona are crucial. This review gives an overview of chromatographic, electrophoretic, mass spectrometric and proteomic methods because these techniques have the advantage to be able to identify and quantify individual proteins adsorbed onto the corona. This capability opens up the possibility to exploit the protein corona for specific cell targeting. © 2014 Springer-Verlag