Atomically Precise Gold–Levonorgestrel Nanocluster as a Radiosensitizer for Enhanced Cancer Therapy

Gold
nanoclusters have become promising radiosensitizers due to
their ultrasmall size and robust ability to adsorb, scatter, and re-emit
radiation. However, most of the previously reported gold nanocluster
radiosensitizers do not have a precise atomic structure, causing difficulties
in understanding the structure–activity relationship. In this
study, a structurally defined gold–levonorgestrel nanocluster
consisting of Au8(C21H27O2)8 (Au8NC) with bright luminescence (58.7%
quantum yield) and satisfactory biocompatibility was demonstrated
as a nanoradiosensitizer. When the Au8NCs were irradiated
with X-rays, they produced reactive oxygen species (ROS), resulting
in irreversible cell apoptosis. As indicated by in vivo tumor formation experiments, tumorigenicity was significantly suppressed
after one radiotherapy treatment with the Au8NCs. In addition,
compared with tumors treated with X-rays (4 Gy) alone, tumors treated
with the nanosensitizer exhibited an inhibition rate of 74.2%. This
study contributes to the development of atomically precise gold nanoclusters
as efficient radiosensitizers.