Titanate Nanotubes Engineered with Gold Nanoparticles and Docetaxel to Enhance Radiotherapy on Xenografted Prostate Tumors

Nanohybrids based on titanate nanotubes (TiONts) were developed to fight prostate cancer by intratumoral (IT) injection, and particular attention was paid to their step-by-step synthesis. TiONts were synthesized by a hydrothermal process. To develop the customengineered nanohybrids, the surface of TiONts was coated beforehand with a siloxane (APTES), and coupled with both dithiolated diethylenetriaminepentaacetic acidmodified gold nanoparticles (Au@DTDTPA NPs) and a heterobifunctional polymer (PEG3000) to significantly improve suspension stability and biocompatibility of TiONts for targeted biomedical applications. The prefunctionalized surface of this scaffold had reactive sites to graft therapeutic agents, such as docetaxel (DTX). This novel combination, aimed at retaining the AuNPs inside the tumor via TiONts, was able to enhance the radiation effect. Nanohybrids have been extensively characterized and were detectable by SPECT/CT imaging through grafted Au@DTDTPA NPs, radiolabeled with 111In. In vitro results showed that TiONtsAuNPsPEG3000DTX had a substantial cytotoxic activity on human PC3 prostate adenocarcinoma cells, unlike initial nanohybrids without DTX (Au@DTDTPA NPs and TiONtsAuNPsPEG3000). Biodistribution studies demonstrated that these novel nanocarriers, consisting of AuNP- and DTXgrafted TiONts, were retained within the tumor for at least 20 days on mice PC3 xenografted tumors after IT injection, delaying tumor growth upon irradiation.