In the present study, AS1411 aptamer conjugated gold nanoclusters (GNCs) have been introduced as a targeted radiosensitizer for enhancing megavoltage radiation therapy efficacy. GNCs with an ultra-small gold core and a bovine serum albumin shell (BSA) as a versatile nano-platform were synthesized and conjugated to AS1411 aptamer (Apt–GNCs). (295 characters)