A facile fluorescent sensor based on carbon dots and for the detection of hyaluronidase activity

Since the sensitivity of the sensing platform using carbon dots (CDs) alone is poor, the development of sensors based on the combination of CDs with other nanomaterials has attracted considerable interest. In this paper, a novel and facile method was established using CDs and Fe3O4 nanoplates (NPs) for the determination of hyaluronidase (HAase) activity. Fe3O4 NPs were introduced to quench the fluorescence of CDs through inner filter effect (IFE) for the first time. The negatively charged HA could bind to the positively charged Fe3O4 NPs via electrostatic attraction to form HA/Fe3O4 NPs complex, resulting in the weakening of the IFE between Fe3O4 NPs and CDs. Hence, the fluorescence of CDs was recovered. With the presence of HAase, HA was hydrolyzed into small fragments which were unable to interact with Fe3O4 NPs. Thus, the fluorescence of CDs was "turn-off" again by Fe3O4 NPs. The activity of HAase was determined in a range of 0.0040-0.12 U mL-1 with a limit of detection of 0.0016 U mL-1. Both the CDs and Fe3O4 NPs were label-free, low-cost and eco-friendly, making the detection system simple and economical. The proposed method provides a new way of designing new sensing platform.