Indium-based quantum dots: Next-generation nanomaterials for bioimaging and diagnostics

Early and sensitive detection of cancer-related biomarkers remains a critical challenge in modern analytical science. In-QDs have emerged as promising analytical nanoprobes due to their tunable photoluminescence, high photostability, narrow emission bandwidths, and lower toxicity compared with conventional cadmium-based quantum dots. These features enable high signal-to-noise fluorescence imaging, multiplexed detection, and improved contrast in complex biological environments. This review summarizes recent advances in indium-based quantum dots, including indium phosphide, indium oxide, indium gallium phosphide, and indium-doped carbon quantum dots. Particular emphasis is placed on synthesis strategies, defect passivation, shell engineering, and surface functionalization approaches that enhance quantum yield, near-infrared emission, and imaging performance. Targeting mechanisms, biodistribution behavior, toxicity considerations, and clearance pathways are also discussed to evaluate the reliability of these nanoprobes in biological systems. Also, current challenges and future perspectives for translating indium-based quantum dots into clinically relevant cancer diagnostics and molecular imaging platforms are highlighted. This review presents a mechanism-oriented and comparative framework linking material design, photophysical behavior, and biomedical performance of indium-based quantum dots. In addition to summarizing recent advances, this review highlights emerging developments in NIR-II emitting In-QDs, biodegradable nanostructures, and scalable green synthesis strategies. It further identifies key translational challenges, including regulatory approval, long-term biosafety, and large-scale manufacturing, providing a forward-looking perspective for clinical application.