Graphene Quantum Dot-Based Biosensors: Recent Advances in Functionalization Strategies and Biomedical Applications

Graphene quantum dots (GQDs) have emerged as a promising class of carbon-based nanomaterials owing to their unique optical properties, tunable surface chemistry, excellent biocompatibility, and high physicochemical stability. These features make GQDs particularly attractive for the development of advanced biosensing platforms. This review provides a comprehensive overview of recent progress in the design, synthesis, and functionalization of GQDs, with a primary focus on their applications in biomedical and biosensors. Various synthesis approaches, including top-down, bottom-up, and chemical methods, are critically discussed in relation to their impact on structural and optical properties. The role of surface engineering and heteroatom doping in modulating sensitivity, selectivity, and signal transduction mechanisms is also highlighted. Furthermore, recent advances in GQD-based biosensors for the detection of clinically relevant biomarkers, environmental analytes, and pathogens are systematically summarized, with emphasis on analytical performance metrics such as sensitivity, selectivity, and limit of detection. In addition, complementary biomedical applications, including bioimaging and therapeutic platforms, are briefly discussed to provide a broader context for the multifunctionality of GQDs. Finally, current challenges and future perspectives toward the rational design of high-performance GQD-based biosensors are outlined.