Determining the selectivity of a tetra-phosphorylated biomimetic peptide towards uranium in the presence of competing cations through the simultaneous coupling of HILIC to ESI-MS and ICP-MS.

A cyclic tetra-phosphorylated biomimetic peptide (pS1368) has been proposed as a promising starting structure to design a decorporating agent of uranyl (UO) due to its affinity being similar to that of osteopontin (OPN), a target UO protein in vivo. The determination of this peptide's selectivity towards UO in the presence of competing endogenous elements is also crucial to validate this hypothesis. In this context, the selectivity of pS1368 towards UO in the presence of Ca, Cu and Zn was determined by applying the simultaneous coupling of hydrophilic interaction chromatography (HILIC) to electrospray ionization (ESI-MS) and inductively coupled plasma (ICP-MS) mass spectrometry. Sr was used as Ca simulant, providing less challenging ICP-MS measurements. The separation of the complexes by HILIC was first set up. The selectivity of pS1368 towards UO was determined in the presence of Sr, by adding several proportions of the latter to UO(pS1368). UO was not displaced from UO(pS1368) even in the presence of a ten-fold excess of Sr. The same approach has been undertaken to demonstrate the selectivity of pS1368 towards UO in the presence of Cu, Zn and Sr as competing endogenous cations. Hence, we showed that pS1368 was selective towards UO in the presence of Sr, but also in the presence of Cu and Zn. This study highlights the performance of HILIC-ESI-MS/ICP-MS simultaneous coupling to assess the potential of molecules as decorporating agents of UO.