A ratiometric fluorescent probe for hyaluronidase detection via hyaluronan-induced formation of red-light emitting excimers.

Hyaluronidase (HAase), which is involved in various physiological and pathological processes, can selectively degrade hyaluronan (HA) into small fragments, and it has been reported as a diagnostic and prognostic biomarker for bladder cancer. Herein, a facile ratiometric fluorescent sensing system for HAase has been developed, which is based on hyaluronan-induced formation of red-light emitting excimers and can realize sensitive detection of HAase with a detection limit of 0.007 U/mL. A positively-charged pyrene analog (N-Py) has been synthesized and then mixed with the negatively-charged HA, due to electrostatic interaction between the two components, aggregation along with the N-Py excimers readily form which emits red light. While in the presence of HAase, the enzyme catalyzes the hydrolysis of HA into small fragments, which in turn triggers disassembly of excimers; consequently the N-Py excimer emission turns into monomer emission. The emission ratio resulted from the excimer-monomer transition can be used as the sensing signal for detecting HAase. The probe features visible-light excitation and red light emission (excimer), which is conducive to reducing possible interference from autofluorescence of biological samples. Furthermore, the assay system can be successfully used to determine HAase in human urine samples with satisfactory accuracy. This strategy may provide a suitable sensitive and accurate assay for HAase as well as an effective approach for developing fluorescent ratiometric assays for other enzymes.