Dual-spot ratiometric microfluidic paper-based analytical device for accuracy and precision improvement

Area of Science:

• Analytical Chemistry
• Biosensing Technology
• Optical Detection

Background:

• Smartphone-based optical detection methods are susceptible to instrumental and environmental errors, compromising analytical accuracy.
• Simultaneous, proximate sample and reference spotting in a dual-spot design mimics double-beam spectrophotometry to mitigate these fluctuations.
• Accurate detection of analytes like ascorbic acid (AA) is crucial in various applications, including clinical diagnostics.

Purpose of the Study:

• To develop and validate a ratiometric microfluidic paper-based analytical device (μPAD) utilizing a dual-spot design for enhanced accuracy in smartphone-based optical detection.
• To selectively detect ascorbic acid (AA) by minimizing interference from other ions.
• To improve the precision and reliability of optical measurements obtained via smartphone imaging.

Main Methods:

• A ratiometric μPAD was fabricated, incorporating green-emissive carbon dots (CDs) and red-emissive ethidium bromide for dual emission.
• A dual-spot configuration was implemented, with one spot for sample detection and a proximate control spot to compensate for fluctuations.
• Sodium fluoride (NaF) was used as a masking agent to eliminate Fe3+ interference with CD fluorescence, enabling selective AA detection.
• Images captured by a smartphone under UV illumination were analyzed using RGB intensity processing via the Color Grab application.

Main Results:

• The dual-spot method significantly improved the analytical precision and accuracy of the μPAD.
• A linear working range for ascorbic acid detection was established from 0 to 125 μM, with a low limit of detection of 2.71 μM.
• The developed μPAD demonstrated successful application in detecting AA in human serum samples, exhibiting high recovery rates (87.27% to 98.52%).

Conclusions:

• The dual-spot ratiometric μPAD design effectively compensates for instrumental and environmental fluctuations, leading to more accurate smartphone-based optical detection.
• This approach offers a robust and sensitive method for the selective quantification of ascorbic acid in complex matrices like human serum.
• The developed μPAD represents a promising advancement for portable, low-cost analytical devices in point-of-care diagnostics and environmental monitoring.