The carbon dots based on Nile red: The preparation and application to probe α-synuclein fibrils

The aggregation of α-synuclein often links to the occurrence and development of Parkinson's disease (PD). It is crucial to detect the α-synuclein fibril or monitor the aggregation of monomer for pharmacological and pathological researches, drug development and clinical diagnosis, etc. In this study, the Nile red (NR)-based carbon dots (NR-CDs) were meticulously designed and prepared. The NR-CDs were sensitive to the microenvironment, exhibiting enhanced fluorescence intensity with the elevated viscosity and decreased polarity. Thus, the NR-CDs exhibited high affinity towards α-synuclein fibril with remarkable red fluorescence enhancement, but did not respond to its monomer. Hence, the NR-CDs were used as the turn-on fluorescence probe to detect and image α-synuclein fibrils both in vitro and in vivo, as well as to monitor the aggregation process of the amyloids. Superior to NR dye, NR-CDs were characteristic of lower toxicity, better water dispersibility and anti-photobleaching resistance. In addition, the NR-CDs were demonstrated to inhibit the aggregation of α-synuclein, holding the potential as the therapeutic agent. The present study provided an effective way of designing the CDs using the small molecular dye as the carbon source to improve the biocompatibility and detectability, while reserve the selective turn-on fluorescence towards amyloid aggregates. This strategy may be generalized to construct more fluorescence probes with desired properties.