Abstract: Complexes comprising a coordinated Cu(II) ion are described herein, which are capable of binding to an extracellular portion of Ctr1 such that the complex with the Cu(II) ion is transported through the Ctr1. The complexes may comprise a Cu(II) ion coordinated to a ligand and to a peptide, wherein the peptide is released upon contact of the complex with an extracellular portion of Ctr1, thereby forming a second complex comprising the ligand, the copper ion and the extracellular portion of Ctr1. Further described herein are uses and methods utilizing the complex, in imaging, in radiation therapy, and for determining a redox state of cells.