Modification of Microfluidic Paper-Based Devices with an Oxidant Layer for Distance Readout of Reducing Substances

Area of Science:

• Analytical Chemistry
• Materials Science
• Biomedical Engineering

Background:

• Microfluidic paper-based analytical devices (μPADs) offer low-cost, portable platforms for chemical analysis.
• Developing simple and effective readout methods for μPADs is crucial for expanding their applications.
• Distance-based detection on μPADs requires robust and easily implementable signal generation strategies.

Purpose of the Study:

• To develop a novel strategy for distance-based readout of reducing substances on μPADs.
• To modify paper cellulose with water-insoluble oxidants for visual detection.
• To demonstrate the applicability of this method for real sample analysis.

Main Methods:

• Paper cellulose was modified with water-insoluble oxidants via a redox reaction with potassium permanganate.
• Reducing substances in sample solutions reacted with the immobilized oxidants, causing a color change and discolored zone formation.
• The distance of the discolored zone correlated with the concentration of reducing substances.

Main Results:

• A yellowish-brown color was developed on the paper channel, which disappeared upon reaction with reducing substances.
• A clear discolored zone was formed, enabling distance-based detection.
• The method was successfully applied to ascorbic acid and captopril assays in real samples, with results comparable to labeled values.

Conclusions:

• The developed method provides a novel and effective approach for distance-based detection of reducing substances on μPADs.
• This strategy broadens the analytical applications of μPADs, particularly for visual and portable analyses.
• The successful application in real samples highlights the potential of this technique for practical diagnostics.