Simultaneous Determination of Oxygen and pH Inside Microfluidic Devices Using Core-Shell Nanosensors

Area of Science:

• Analytical Chemistry
• Materials Science
• Biotechnology

Background:

• Simultaneous online monitoring of oxygen and pH is crucial for various chemical and biological processes.
• Existing methods often face limitations in cost, complexity, or stability in challenging media.
• Development of robust, sensitive, and easily readable nanosensors is needed for advanced process analysis.

Purpose of the Study:

• To develop and characterize a novel core-shell nanosensor system for simultaneous, contactless detection of oxygen and pH.
• To enable inexpensive and efficient real-time analysis using adapted oxygen meters and frequency-domain phase shift measurements.
• To demonstrate the application of these nanosensors in monitoring enzymatic reactions in microreactors.

Main Methods:

• Fabrication of core-shell nanoparticles (180 nm diameter) using poly(styrene-block-vinylpyrrolidone).
• Incorporation of a platinum-based oxygen indicator (PtTPTBPF) in the core and a BF2-chelated tetraarylazadipyrromethene (aza-BODIPY) pH indicator in the shell.
• Utilized dual lifetime referencing in the frequency domain (phase shift measurements) for contactless readout.

Main Results:

• Achieved oxygen detection resolution of 0.5-2.0 hPa at low concentrations and 4-8 hPa at ambient levels.
• Obtained pH resolution of 0.03-0.1 pH units within a dynamic range (apparent pKa 7.23 ± 1.0).
• Demonstrated successful online monitoring of pH during enzymatic transformation of Penicillin G in batch and flow microreactors.

Conclusions:

• The developed core-shell nanosensors provide a powerful, stable, and spectrally compatible platform for simultaneous oxygen and pH monitoring.
• The system offers advantages of red-light excitation, near-infrared emission, and high stability in diverse aqueous environments.
• This technology enables efficient real-time analysis of enzymatic processes in miniaturized reactor systems.