**Highly Hydrophilic Gold Nanoparticles as Carrier for Anticancer Copper(I) Complexes: Loading and Release Studies for Biomedical Applications**

**Ilaria Fratoddi 1, Iole Venditti 2,\*, Chiara Battocchio 2, Laura Carlini 2, Simone Amatori 1, Marina Porchia 3,\*, Francesco Tisato 3, Federica Bondino 4, Elena Magnano 4, Maura Pellei 5 and Carlo Santini 5**


Received: 2 May 2019; Accepted: 15 May 2019; Published: 20 May 2019

**Abstract:** Gold nanoparticles (AuNPs), which are strongly hydrophilic and dimensionally suitable for drug delivery, were used in loading and release studies of two di fferent copper(I)-based antitumor complexes, namely [Cu(PTA)4] + [BF4] − (A; PTA = 1, 3, 5-triaza-7-phosphadamantane) and [HB(pz)3Cu(PCN)] (B; HB(pz)3 = tris(pyrazolyl)borate, PCN = tris(cyanoethyl)phosphane). In the homoleptic, water-soluble compound A, the metal is tetrahedrally arranged in a cationic moiety. Compound B is instead a mixed-ligand (scorpionate/phosphane), neutral complex insoluble in water. In this work, the loading procedures and the loading e fficiency of A and B complexes on the AuNPs were investigated, with the aim to improve their bioavailability and to obtain a controlled release. The non-covalent interactions of A and B with the AuNPs surface were studied by means of dynamic light scattering (DLS), UV–Vis, FT-IR and high-resolution x-ray photoelectron spectroscopy (HR-XPS) measurements. As a result, the AuNPs-A system proved to be more stable and e fficient than the AuNPs-B system. In fact, for AuNPs-A the drug loading reached 90%, whereas for AuNPs-B it reached 65%. For AuNPs-A conjugated systems, a release study in water solution was performed over 4 days, showing a slow release up to 10%.

**Keywords:** gold nanoparticles; copper(I) complexes; conjugates; drug delivery; anticancer compounds
