Extruded filament electrodes for lactate biosensing in continuous-injection paper-based microfluidic devices

Area of Science:

• Electrochemistry
• Materials Science
• Analytical Chemistry

Background:

• Paper-based analytical devices (μPADs) offer low-cost, portable sensing solutions.
• Efficient fabrication of integrated electrode systems for μPADs remains a challenge.
• Lactate detection is crucial for various biomedical and sports monitoring applications.

Purpose of the Study:

• To develop a straightforward method for fabricating 3D-printed electrodes integrated into μPADs for lactate quantification.
• To optimize the μPAD system for rapid, sensitive, and low-volume sample analysis.
• To demonstrate the analytical applicability of the fabricated μPADs for lactate determination in real sweat samples.

Main Methods:

• Fabrication of poly(methyl methacrylate) (PMMA) molds using a 3D printing pen and carbon black filament.
• Modification of working electrodes with Prussian Blue (PB), lactate oxidase (LOx)/chitosan, and Nafion.
• Integration of a 3-electrode thermoplastic chip with μPADs, utilizing radial flow for sample analysis.
• Characterization of μPADs using food dye, ferricyanide, and optimization of paper substrate pore size and injection volume.

Main Results:

• The integrated μPAD system demonstrated rapid responses with sharp, intense transient signals.
• Optimized μPADs exhibited a linear range of 0.5 to 4 mmol L⁻¹ for lactate determination.
• The system successfully quantified lactate in real sweat samples using only 2 μL of sample.

Conclusions:

• A facile approach for fabricating integrated 3D-printed electrodes on μPADs was successfully developed.
• The developed μPADs offer a promising platform for rapid, low-volume lactate quantification.
• This technology opens avenues for new sensing applications requiring minimal sample volumes.