Fluorescence detection of laccases activity by the photoinduced electron transfer (PET) process

Laccases play a vital role in some physiological processes, for example in morphogenesis, carbon cycle, and defense against parasitism. So, designing a high-sensitivity accurate method is essential for researchers. In this study, a simple fluorescence method based on the function of carbon nitride (g-C₃N₄) by dopamine is synthesized. For the design of this sensor, carbon nitride (g-C₃N₄) is initially synthesis by using a simple method, which is carried out by heating melamine at 550 °C for 3 h and modifying it with dopamine by a linker such as glutaraldehyde. However, the g-C₃N₄-Dopa produced by this method, with an excitation wavelength of 330 nm, has a fluorescence emission at 466 nm. When laccase and g-C₃N₄-Dopa were mixed, dopamine with redox property was oxidized to dopaquinone; this causes the phenomenon of photoinduced electron transfer (PET) process between g-C₃N₄ and the dopaquinone. Hence, fluorescence quenching occurs due to this phenomenon. As a result of these discussions, a sensor for the laccase activity was designed based on the fluorescence quenching degree, supporting a linear range of 0.0-400.0 U L^-1 with the detection limit of 2.0 U L^-1. Using this sensor, the activity of the laccase enzyme in the human serum samples is measured. Dopamine-functionalized carbon nitride was prepared and utilized for the highly sensitive detection of laccases activity.