Carbon Dot/Naphthalimide Based Ratiometric Fluorescence Biosensor for Hyaluronidase Detection.

Bladder cancer is the leading cause of death in patients with genitourinary cancer. An elevated level of hyaluronidase (HAase) was found in bladder cancer, which acts as an important biomarker for the early diagnosis of bladder cancer. Hence, there is a need to develop a simple enzymatic assay for the early recognition of HAase. Herein, we report a simple, sensitive, and ratiometric fluorescence assay for HAase detection under physiological conditions. The fluorescence assay was constructed by the adsorption of cationic carbon dots and positively charged naphthalimide on negatively charged hyaluronic acid and the development of a Förster resonance energy transfer (FRET) mechanism from carbon dots to a naphthalimide fluorophores. The hyaluronidase enzyme cleaves the hyaluronic acid in this assay, and breaking down the FRET mechanism induces ratiometric changes. A detection limit of 0.09 U/mL was achieved, which is less than the HAase level found in normal human body fluids. Moreover, this assay may be used for diagnosing HAase-related diseases.