Development of a novel ratiometric electrochemical sensor for monitoring β-galactosidase in Parkinson's disease model mice

Rapid, simple, accurate and highly sensitive detection of enzymes is essential for early screening and clinical diagnosis of many diseases. In this study, we report the fabrication of a turn-on ratiometric electrochemical sensor for the in situ determination of β-Galactosidase (β-Gal) based on surface engineering and the design of a molecular probe (Pygal) specific for β-Gal recognition. First, Pygal probe was synthesized and characterized, and then co-assembled with the methylene blue (MB) internal reference probe on the surface of single-wall carbon nanotubes (SWCNT)-modified carbon fiber microelectrode (CFME). The resulting CFME/SWCNT/MB + Pygal sensor is activated in the presence of β-Gal giving one peak at 0.33 V originating from the oxidation of the product of Pygal enzymatic hydrolysis (PyOH). Another oxidation peak attributed to MB appears simultaneously at -0.28 V allowing the construction of a ratiometric electrochemical sensor for β-Gal detection with improved sensitivity and accuracy. The sensor showed a linear response to β-Gal in a wide concentration range from 1.5 to 30 U L-1 and a low detection limit of 0.1 U L-1. Moreover, the sensor demonstrated excellent selectivity against several biologically relevant hydrolases and redox-active molecules. Finally, the combination of excellent electrochemical performance and favorable physicochemical properties of CFME allowed the determination of β-Gal in the whole blood of Parkinson's Disease (PD) model mice. The workflow reported in this study provides a strategy for the design and development of sensors for the in vivo monitoring of other enzymes important for the early diagnosis of different health issues.