On-line fast column switching SEC x IC separation combined with ICP-MS detection for mapping metallodrug-biomolecule interaction

Comprehensive fast column switching two-dimensional chromatography has been combined for the first time with ICP-MS detection. The developed, fully automated on-line 2-D system was designed for intact protein separation. Absolute detection limits in the pmol-range were obtained for proteins considering the hetero-elemental tag sulfur, which was detected as SO(+) employing dynamic reaction cell technique. The method was implemented for screening the interaction of metallodrugs with proteins in biological samples, which play a key role in the preclinical and clinical drug development. As a key advance, this tool-set is capable of handling any candidate metallodrug. Since covalent and non-covalent interactions are essential in this context, a native orthogonal separation was a prerequisite. Hence, the first dimension involved a size-selective separation, which was followed on-line by ion exchange chromatography employing two parallel monolithic discs. The cycle time of the ion exchange using these disks was 3 min. Hence, while gradient elution of one monolithic disk was performed within 3 min, the second disk was loaded with the next fraction of the size exclusion column. In a feasibility study, cisplatin was studied in serum samples (ex vivo incubation) demonstrating the potential of the method in preclinical studies on candidate drugs.