Structural investigation of Cu(I) Coordination Compounds and Gold Nanorods as Drug Delivery Systems

This study investigates the molecular and electronic structure of composite nanoparticles, designed for biomedical applications, conjugated to Cu(I) complexes of a chelating agent (L) functionalized with the antineoplastic drug lonidamine and two phosphane monodentate co-ligands, namely 1,3,5-triaza-7-phosphaadamantane (PTA) for the complex [(PTA)2Cu(L)]PF6, or triphenylphosphine (PPh3) for the complex [(PPh3)2Cu(L)]PF6 (Fig. 1). Due to their lipophilic nature, direct biomedical applications are precluded; hence, we conjugated these complexes with gold nanorods (AuNRs), acting as a well-established drug delivery system.1 To determine the behaviour, the coordination chemistry of the complexes after conjugation with nanorods and subsequent exposure to aqueous solutions is mandatory from a biomedical point of view and relevant for material understanding. The [(PTA)2Cu(L)]PF6 and [(PPh3)2Cu(L)]PF6 complexes were characterized in their dry and pristine states using X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Fine Structure (XAFS) analysis (Fig. 2). Furthermore, the Cu-coordination in [(PTA)2Cu(L)]PF6 complex was examined in both its AuNR-functionalized dry form and in aqueous solution.2 This comprehensive investigation facilitates the determination of Cu-coordination geometry and provides deep insights into the molecular structures of the complexes, showing modifications upon interaction with AuNRs and after their dissolution in water.