Surface-Engineered Carbon Dots for Monitoring of Lysosomal Viscosity and Organelle Dysfunction

The development of robust, photostable nanoprobes for precise organelle targeting remains a cornerstone in chemosensing and advanced bioimaging. Alterations in the lysosomal microenvironment serve as an indicator of organelle health and disease progression. Herein, a sustainable synthetic strategy is presented for benzothiazole-modified carbon dots (LysoDots), engineered for specific lysosome localization and viscosity monitoring. LysoDots display a viscosity-dependent fluorescence enhancement in glycerol-water systems while remaining insensitive to physiological pH and temperature variations. This turn-on response allows for the high-fidelity tracking of lysosomal microviscosity changes induced by exogenous stimuli, such as nystatin, and endogenous processes like rapamycin-induced autophagy. Confocal imaging demonstrates a remarkable colocalization of LysoDots with the commercial lysosome marker, LysoTracker Green (LTG), showing a Pearson's correlation coefficient of 0.92 in CAL-33 oral carcinoma cells, with the red emission effectively differentiating lysosomal viscosity profiles between cancerous and non-cancerous cells. Furthermore, the LysoDots were successfully employed in a neuronal model, SH-SY5Y cells, where the probe effectively tracked glutamate-induced lysosomal dysfunction, mimicking the pathology of lysosomal storage disorders, along with the viscosity restoration mediated by trehalose. These findings highlight the potential of LysoDots as a biocompatible, photostable, multi-functional nanomaterial for long-term monitoring of lysosomal dynamics and cellular homeostasis.