Carbon quantum dots in biomedical applications

Abstract

Carbon quantum dots (CQDs) have emerged as an important class of carbon-based fluorescent nanomaterials owing to their tunable photoluminescence, favorable aqueous dispersibility, and modifiable surface chemistry, which support diverse biomedical applications. This review critically summarizes recent advances in biofabricated CQDs with particular emphasis on green synthesis approaches, physicochemical characterization, surface engineering, and biomedical performance. Various synthesis strategies, including hydrothermal, microwave-assisted, electrochemical, and biomass-derived methods, are comparatively evaluated in terms of scalability, reproducibility, biocompatibility, and translational potential. In addition, the biomedical applications of CQDs in bioimaging, biosensing, targeted drug delivery, cancer theranostics, and antimicrobial platforms are comprehensively discussed with recent literature updates. The influence of surface functionalization on colloidal stability, targeting efficiency, cellular uptake, and biological interactions is also examined. Furthermore, current evidence from in vitro and in vivo studies regarding the biosafety and toxicity profiles of CQDs is critically analyzed. Despite significant progress, several challenges remain, including large-scale synthesis standardization, long-term toxicity evaluation, batch-to-batch reproducibility, and regulatory limitations associated with clinical translation. Future advancements in scalable fabrication techniques, multifunctional surface engineering, and safety assessment strategies may accelerate the development of CQDs-based nanomedicine platforms for diagnostic and therapeutic applications.

Keywords: Carbon quantum dots, Green synthesis, Bioimaging, Targeted drug delivery, Biosensing, Theranostics, Nanomedicine