Smart fluorogenic tools: From designing principles to visualization of multistep protein aggregation

Protein aggregation is implicated in numerous pathological conditions, including neurodegenerative diseases, cancers, and cardiovascular disorders, making it a crucial target for innovative diagnostics and therapeutics. Recent advancements in organic fluorescent probes have transformed the visualization of protein aggregation, enabling non-invasive, real-time imaging with unprecedented sensitivity and resolution. This review provides a comprehensive exploration of cutting-edge strategies for designing and applying organic fluorescent probes, with a focus on key classes such as aggregation-induced emission (AIE) probes, molecular rotors, and conjugated polyelectrolytes. These probes have significantly advanced our ability to detect distinct aggregation stages, from early oligomer formation to mature fibrils, while overcoming challenges such as fluorescence quenching and specificity. By summarizing innovations in multi-modal imaging and near-infrared (NIR) probes, we highlight their strengths and discuss how these advancements may inspire the development of next-generation probes tailored for studying protein aggregation. Finally, we identify opportunities to enhance probe design for improved biocompatibility, quantitative capabilities, super-resolution imaging and therapeutic integration, positioning next-generation fluorescent probes as transformative tools in clinical and research settings.