Study of Cu coordination core in copper complexes grafted onto Au nanorods

Copper coordination compounds have been developed as a promising alternative to the classic anticancer metallodrugs. In our quest for suitable organic ligands that exhibit a remarkable cytotoxic activity, we focused our attention on the synthesis of Cu(II)-complexes of bis(azol-1-yl)acetates and related esters or amides. However, since these compounds have low solubility in an aqueous medium, it is necessary to design a strategic approach allowing for drug delivery. In our recent works, we are exploring the possibility to conjugate the copper complexes with hydrophilic gold nanoparticles (AuNPs), to improve their solubility and stability in water, increasing their bioavailability. The preliminary studies confirmed the success of the method. An accurate study of the Cu coordination core is a mandatory step to understand the grafting to Au-NPs and the Au-NP/Cu-complexes stability in order to individuate the suitable procedures for controlled drug release. In this work, the local atomic structure and coordination chemistry around Cu and Au atoms in different Au-NP/Cu-complexes [5] has been probed by X-ray absorption fine structure (XAFS). The data provide deep insight into the interaction between Au-NP and Cu(II)-complexes shedding light on the mechanisms for drug loading/release. Such information is relevant to reliably understand the activity of these novel drug delivery systems representing a step forward in developing specific metal-based anticancer drugs.