Elemental labeling of peptides

In the field of pharmaceutical and diagnostic medicine peptides play an important role and their quantification in biological systems affords selective and sensitive analytical methods. Our project - a cooperation between the Division of Analytical Chemistry, BOKU-Vienna and the Medical University of Vienna - aims at the development of novel strategies for peptide quantification employing elemental labeling. The integration of this strategies in biomedical research opens the way to new analytical concepts for preclinical studies, as accurate absolute peptide quantification and investigation of peptide interaction with cellular targets can be performed. A drug, which is currently tested in preclinical studies, will serve as a model substance for the planned research. The peptide showed promising results in tissue protection by reducing tissue inflammation and tissue edema thereby reducing myocardial infarct sizes (in patients undergoing catheter-based reopening of occluded coronary vessels). For enhancement of analytical sensitivity the peptide will be labeled with an indium atom employing a macrocyclic chelate as complexing moiety. For the first time detection and quantification of an elemental labeled drug in in vitro cell experiments will be performed via liquid chromatography combined with inductively coupled plasma mass spectrometry (LC-ICP-MS). Moreover, the striking advantages of the approach will be demonstrated via peptide/protein interaction studies. Important information on the increased sensitivity and selectivity of the new approach, as well as quantitative information on the cellular uptake and possible interaction partners of the drug will be obtained. Novel findings on the stability of different labeling chemistries will have an important impact on the field of elemental labeling in bio-analysis, especially on the emerging topic of biomarker discovery and quantification.

In the framework of the project Elemental labeling of peptides analytical strategies for quantification of biomolecules in biomedical samples have been developed combining elemental labeling with highly sensitive detection via inductively coupled plasma mass spectrometry (ICP-MS). Future applications of the novel technique are the quantification of e.g. peptide drugs and biomarkers at ultratrace concentrations. The implementation of the concept in routine diagnostics demands not only for a detailed knowledge of elemental labeling techniques, but also for a careful characterization of the produced elemental labeled compounds and of the detection process. Hence, the project comprised basic research addressing the development of strategies for elemental labeling of biomolecules, the characterization of the labeled compounds, and the development of separation and detection methods foe quantitative application of the concept of elemental labeling in the biological and medical field. The novel methods have been successfully applied for quantification of a candidate peptide drug in cooperation with the Skin & Endothelium Research Division (SERD) at the Medical University of Vienna. Moreover, the process of elemental labeling has been optimized utilizing a specific antibody, which has finally enabled the highly sensitive and specific quantification of a cancer biomarker. The results have been published in international scientific journals and are the base for future development of elemental analytical strategies for diagnostic analysis of liquid clinical samples and for imaging of tissue samples.