New members of the lanthanide titanium cluster family: Janus nanoclusters, and their optical imaging and photodynamic therapy

Abstract

In this work, a new member of the low-symmetry lanthanide titanium clusters family (Ln4Ti14), characterized by a Janus distribution at the cluster core was discovered. The Ln4Ti14 nanocluster, formed by stepwise assembly, is surrounded by a dense protective layer of ligands, ensuring the cluster's stability in solution. Variation of the Ln(III) ions allows for easy control of the energy transfer pathway, enabling switching between high-resolution bio-optical imaging and photodynamic therapy (PDT). Specifically, Eu4Ti14, with its efficient antenna effect, exhibits bright, Eu(III)-characteristic emission and enables high-resolution optical imaging within the mitochondria of living cells and in zebrafish. Notably, Gd4Ti14 rapidly generates a reactive oxygen species (ROS) storm upon light irradiation, effectively damaging mitochondria and exhibiting outstanding PDT efficacy both at the cellular level and in tumor-bearing mouse models. The near-complete ablation of tumors in the tumor-bearing mouse model and H&E staining of sections from key organs demonstrate that Gd4Ti14, as a novel photosensitizer, possesses both outstanding PDT efficacy and excellent biosafety. This work not only opens new horizons for the controllable assembly of lanthanide titanium clusters with specific connectivity and shapes, but also opens up a new blueprint for lanthanide titanium clusters as novel nanodiagnostic and therapeutic platforms.