Penicillamine-Capped Red-Emitting Gold Nanoclusters for Therapeutic Application

Subnanometer-sized metal nanoclusters (NCs) with diameters <2 nm have emerged as promising materials in biomedical applications. Here, we report the synthesis of near-infrared (NIR)-emitting Au14 nanoclusters using a small therapeutic molecule, d-penicillamine (DPA), as a surface stabilizing agent. We have characterized the morphology and composition of as-synthesized NCs using electron microscopy and mass spectrometry techniques. The photophysics of the NCs was investigated by UV–vis and photoluminescence (PL) spectroscopy. We found molecule-like features with three distinctive absorption bands at 390, 456, and 590 nm and a photoemission band at 696 nm. We observed that Au NCs specifically inhibited cancer cells dose-dependently through preferential uptake and imparted significant intracellular ROS. They did not show any acute toxicity in C57BL/6 mice at a dosage of 10 mg/kg, with predominant accumulation in the kidneys at the end of 24 h.