A digital microfluidic approach to homogeneous enzyme assays

Area of Science:

• Biochemistry
• Analytical Chemistry
• Microfluidics

Background:

• Traditional microfluidic devices use continuous fluid streams.
• Digital microfluidics manipulates discrete droplets for greater flexibility.
• Enzymatic analyses require precise control over reaction conditions.

Purpose of the Study:

• To demonstrate the application of digital microfluidics for enzymatic analyses.
• To evaluate the sensitivity and reproducibility of digital microfluidic assays.
• To compare digital microfluidics with conventional methods for enzyme kinetics studies.

Main Methods:

• Utilized a digital microfluidic device to perform enzymatic reactions with discrete droplets.
• Employed alkaline phosphatase and fluorescein diphosphate as a model system.
• Detected fluorescent product using a fluorescence plate reader.
• Investigated enzyme kinetics and inhibition effects.

Main Results:

• Achieved substrate quantitation with a 2-order linear range and a detection limit of 7.0 x 10^-20 mol.
• Demonstrated reproducible enzyme kinetics (Km, kcat) comparable to conventional assays.
• Showed that a nonionic surfactant improved device longevity without impacting enzyme activity.
• Developed a prototype for multiplexed enzyme analyses.

Conclusions:

• Digital microfluidics provides a sensitive and reproducible platform for enzymatic assays.
• The digital format allows for detailed analysis in significantly reduced reaction volumes.
• This technology surpasses conventional methods in sensitivity and efficiency for enzyme activity and substrate concentration determination.