Atomic (HPLC-ICP-MS) and molecular mass spectrometry (ESI-Q-TOF) to study cis-platin interactions with serum proteins

The judicious use of cis-Pt as an intravenously administrable Pt(II) drug for chemotherapy requires the evaluation of its interactions with blood proteins. Therefore, the combined use of modern analytical chemical speciation and of analytical proteomics approaches to study these interactions is described here. The method involves incubation of cis-Pt with standard proteins and human serum samples. The separation of the proteins is conducted by liquid chromatography in an anion exchange column (Mono Q). Simultaneous molecular detection by UV absorption (280 nm) and elemental detection (195Pt) using inductively coupled plasma mass spectrometry (ICP-MS) are performed. Using this set-up, the effects of the incubation time as well as the drug concentration on cis-Pt interactions with transferrin, albumin and innmunoglobulin G were studied. In addition, the nature of interactions was also investigated by means of electrospray mass spectrometry (ESI-Q-TOF) of the intact protein. Transferrin and albumin showed different interactions, binding one and four cisplatin molecules, respectively. Also, some typical proteomic studies were initiated by tryptic digesting the transferrin and albumin cis-Pt complexes followed by capillary-LC-ICP-MS and ESI-Q-TOF parallel detection of the peptides obtained. The capLC-ICP-MS chromatogram provided clear evidence of Pt-containing peptides remaining after tryptic digestion.