Dopant concentration-dependent size-controlled spherical Cu²⁺-doped Zn Au nanocluster assemblies for efficient cancer...

Assembled metal nanoclusters are a promising material for imaging and optical applications, but face challenges in anticancer therapy due to poor cellular uptake arising from their large size. To address this, a Cu²⁺ ion-doping strategy was employed in a zinc ion-induced gold nanocluster (Zn Au NC) assembly to enhance cellular uptake efficiency. This was achieved by varying doping levels, which enabled control over the size and crystallinity of the doped assembly, thereby enhancing cellular uptake and therapeutic performance. The smallest Cu²⁺ ion-doped Zn Au NC assembly (3.02 nm) exhibited the best anticancer activity with an IC₅₀ value of 107 μg mL^-1 (equivalent to 1.6 μg mL^-1 of Cu) against HeLa cells. It also exhibited the highest efficacy against MCF-7 cells, with an IC₅₀ value of 132 μg mL^-1. Moreover, the dopant-induced red luminescence at 590 nm facilitated cellular imaging, demonstrating combined therapeutic and diagnostic functionality. These findings establish metal ion doping as an effective route to tune the structural and biomedical properties of nanocluster assemblies.