Carbon dots in cancer therapy: a novel approach to targeted drug delivery and reduced toxicity in gallbladder cancer.

Biliary tract cancers (BTCs), including cholangiocarcinoma and gallbladder carcinoma, are highly aggressive malignancies associated with poor prognosis, late diagnosis, and limited therapeutic options. Conventional chemotherapy offers only modest survival benefits because of inadequate tumor selectivity, rapid systemic clearance, dose-limiting toxicity, and the emergence of chemoresistance. Carbon quantum dots (CQDs) have emerged as promising nanotheranostic agents owing to their ultrasmall size, tunable photoluminescence, excellent aqueous dispersibility, biocompatibility, and versatile surface chemistry, enabling simultaneous drug delivery, imaging, and phototherapy. This review summarizes the evolution of carbon dots into structurally engineered CQDs and discusses their physicochemical, optical, and biological properties that underpin their biomedical applications. Particular emphasis is placed on recent advances in CQD-based drug delivery, fluorescence bioimaging, photothermal therapy, photodynamic therapy, and multifunctional theranostic platforms relevant to BTC management. Although direct studies on CQDs for BTC remain limited, emerging evidence from hepatobiliary and other gastrointestinal cancers highlights their potential to improve targeted drug delivery, tumor imaging, and therapeutic efficacy. The review further identifies critical challenges to clinical translation, including the lack of BTC-specific preclinical models, insufficient pharmacokinetic and long-term biosafety data, and the need for standardized, reproducible CQD synthesis and functionalization protocols. Finally, future research directions are discussed, emphasizing tumor-targeted CQD engineering, multimodal therapeutic strategies, and integration with precision oncology. Collectively, CQDs represent a promising nanoplatform for the development of targeted, image-guided, and minimally invasive approaches for the diagnosis and treatment of biliary tract cancers.