A Dual-Readout Photonic Sensor for Simultaneous Measurement of Enzyme Activity and Concentration.

Area of Science:

• Biomedical Engineering
• Analytical Chemistry
• Biochemistry

Background:

• Enzyme assays are crucial for biology and clinical diagnostics, often requiring separate measurements for activity and concentration.
• Current methods necessitate distinct assays (e.g., ELISA for concentration, absorbance for activity), complicating quantification and comparison.
• Simultaneous measurement of both parameters is desirable for comprehensive enzyme characterization.

Purpose of the Study:

• To develop a multiplex disposable photonic biosensor for simultaneous measurement of enzyme activity and concentration.
• To demonstrate the utility of this dual-mode assay for quantifying human Cathepsin-L.
• To establish a prototype for future dual-mode photonic enzyme assays.

Main Methods:

• Utilized a ring resonator-bound antibody for enzyme capture, inducing a resonance red shift.
• Employed enzyme-mediated substrate degradation, causing a resonance blue shift, for activity measurement.
• Validated the assay with human Cathepsin-L and tested in a complex human serum matrix.

Main Results:

• Achieved simultaneous measurement of enzyme concentration and activity using a single photonic platform.
• Demonstrated analytical performance with low limits of detection: 2.0 ng·mL⁻¹ for concentration and 1.8 ng·mL⁻¹ for activity.
• Confirmed the assay's effectiveness in a biologically relevant matrix using 25 human serum samples.

Conclusions:

• The developed multiplex photonic biosensor enables simultaneous quantification of enzyme activity and concentration.
• The assay is highly sensitive and suitable for detecting Cathepsin-L, relevant to diseases like COVID-19, kidney failure, and cancer.
• This technology serves as a valuable tool for Cathepsin-L detection and a model for developing other dual-mode photonic enzyme assays.