The application of carbon dot-based nanoprobes in advanced optical imaging and multimodality imaging

Carbon dots (CDs), as versatile fluorescent nanomaterials, demonstrate immense potential for revolutionizing bioimaging due to their facile synthesis, excellent photophysical properties, biocompatibility, and tunable surface chemistry. Their high quantum yield, superior photostability, and tunable emission wavelengths make them ideal materials for highly sensitive fluorescence imaging, including confocal microscopy and super-resolution imaging techniques, enabling detailed subcellular visualization. Their unique fluorescence lifetime characteristics also facilitate fluorescence lifetime imaging microscopy (FLIM) for sensing microenvironments and multiplexing. Furthermore, CDs excel in multiphoton excitation microscopy (MPEM), utilizing their large multiphoton absorption cross-sections for deep-tissue imaging with reduced background and photodamage. Crucially, the ease of functionalizing CDs allows for their integration with other contrast agents (e.g., magnetic nanoparticles, radionuclides, photosensitizers), enabling the construction of sophisticated multimodal nanoprobes. These probes synergistically combine the high sensitivity and resolution of optical imaging with the deep penetration capabilities of techniques such as magnetic resonance imaging (MRI), positron emission tomography (PET), computed tomography (CT), and photoacoustic imaging (PAI). Such multimodal systems provide complementary anatomical, functional, and molecular information, significantly enhancing diagnostic accuracy and enabling real-time image-guided interventions. This review focuses on the applications of CD-based nanoprobes in cutting-edge advanced optical imaging and multimodality imaging technologies. It begins with a brief introduction to mainstream synthesis methods and functional modifications of current CDs. Then, based on the current research landscape, it details the applications and principles of CDs in advanced optical imaging and multimodal imaging. Moreover, we have made a brief summary of the biosafety of carbon dots in biological applications. Finally, it outlines their challenges and prospects in biomedical applications.