Functionalization of new anticancer Pt(II) complex with transferrin receptor binding peptide

Abstract

One strategy to improve the selectivity of metallocompounds is to functionalize them by conjugation with biomolecules as folate, hormones, and peptides. In this work, we describe the conjugation of a transferrin receptor binding peptide of sequence HAIYPHRH to a Pt(II) bis(2-pyridylmethyl)glycine complex. The complex was fully characterized by mass spectrometry and 1D and 2D NMR. Among several synthetic strategies, the preparation of bis-(2-pyridylmethyl)glycyl-NH-HAIYPHRH by solid-phase peptide synthesis, its purification by HPLC, followed by the coordination of Pt(II) was the successful method. The metal coordination was studied by 1H NMR and 1H-15N HSQC. The results show the metal ion interacts by fast exchange reaction with the two terminal histidines and slow exchange with bis(2-pyridylmethyl)glycine moiety. The compounds presented inhibition of growth for renal cancer cells; therefore, it is not an effect of the peptide as the precursor, [PtCl(bis(2-pyridylmethyl)glycine)], presents similar GI50. The peptide-Pt(II) complex presents a high binding constant with serum albumin and demonstrated to bind covalently to DNA by electrophoretic mobility assays. The work represents a complete description of the coordination of platinum in this system and demonstrates the challenges to develop new metallopeptides.