Polypyrrole-based double rare earth hybrid nanoparticles for multimodal imaging and photothermal therapy

Nanotheranostic agents that can simultaneously provide real-time tracking and accurate treatment at tumor sites are playing an increasingly important role in medicine. Herein, a novel polypyrrole (PPy)-based theranostic agent containing double rare-earth elements (PPy@BSA-Gd/Dy NPs) was successfully synthesized via an integrated strategy combining biomineralization and oxidation polymerization. The obtained PPy@BSA-Gd/Dy NPs with a diameter of approximately 59.48 ± 6.12 nm exhibited excellent solubility, long-term stability, superior biocompatibility, and negligible toxicity. Importantly, due to its intrinsic paramagnetic and strong X-ray attenuation ability, this agent demonstrated brilliant imaging performance in both T1/T2-weighted magnetic resonance imaging (MRI) and X-ray computed tomography (CT) imaging in vitro and vivo. Additionally, with an excellent photothermal conversion efficiency (26.61%) upon irradiation by an 808 nm laser, this theranostic agent showed significant photothermal cytotoxicity against HeLa cells and 4T1 cells in vitro and antitumor efficacy through intravenous injection in vivo. Meanwhile, biodistribution and blood circulation were also used to explore its fate in vivo. In summary, this study highlighted the versatility and practicability of PPy@BSA-Gd/Dy NPs and also suggested that the agent may be a promising candidate for T1/T2-weighted MRI/CT tri-modal imaging guided photothermal cancer therapy.