PEGylated Rhenium Nanoclusters: A Degradable Metal Photothermal Nanoagent for Cancer Therapy

A common issue of functional nanoagents for potential clinical translation is whether they are biodegradable or renal clearable. Previous studies have widely explored noble metal nanoparticles (Au, Pd) as the first generation of photothermal nanoagents for cancer therapy, but all of the reported noble metal nanoparticles are non-degradable. On the other hand, rhenium (Re), one of noble and precious metals with high atomic number (Z = 75), has been mainly utilized as jet superalloy or chemical catalyst, but the biological characteristics and activity of Re nanoparticles have never been evaluated until now. To echo these issues, here we report a simple and scalable liquid-reduction stragety to synthesize PEGylated Re nanoclusters, which exhibit intrinsically high photothermal conversion efficacy (33.0%) and high X-ray attenuation (21.2 HU·mL·mg-1), resulting in excellent photothermal ablation (100% tumor elimination) and higher CT enhancement (15.9 HU mL mg-1 for commercial iopromide in clinic) . Impressively, biocompatible Re nanoclusters can be degradable into renal clearable ReO4- ions after the exposure of H2O2, and thus depicts much higher renal clearance efficiency than conventional gold nanoparticles. This work reveals the potential of theranostic application of metallic Re nanoclusters with both biodegradable and renal clearable properties, and provides the insights into the design of degradable metallic platform with high clinical prospects.