Microfluidic paper-based analytical devices (microPADs) are emerging as cost-effective and portable platforms for point-of-care assays. A fundamental limitation of microPAD fabrication is the imprecise nature of most methods for patterning paper. The present work demonstrates that paper patterned via wax printing can be miniaturized by treating it with periodate to produce higher-resolution, high-fidelity microPADs. The optimal miniaturization parameters were determined by immersing microPADs in various concentrations of aqueous sodium periodate (NaIO4) for varying lengths of time. This treatment miniaturized microPADs by up to 80% in surface area, depending on the concentration of periodate and length of the reaction time. By immersing microPADs in 0.5-M NaIO4for 48 hours, devices were miniaturized by 78% in surface area, and this treatment allowed for the fabrication of functional channels with widths as small as 301 µm and hydrophobic barriers with widths as small as 387 µm. The miniaturized devices were shown to be compatible with redox-based colorimetric assays and enzymatic reactions. This miniaturization technique provides a new option for fabricating sub-millimeter-sized features in paper-based fluidic devices without requiring specialized equipment and could enable new capabilities and applications for microPADs.
In this paper we describe the fabrication of novel 3D microfluidic paper‐based analytical devices (3D‐μPADs) and a 3D microfluidic thread/paper‐based analytical device (3D‐μTPAD) to detect glucose and BSA through colorimetric assays. The 3D‐μPAD and 3D‐μTPAD consisted of three (wax, heat pressed wax‐printed paper, single‐sided tape) and four (hole‐punched single‐sided tape, blank chromatography circles, heat‐pressed wax‐printed paper, hole‐punched single‐sided tape containing trifurcated thread) layers, respectively. The saturation curves for each assay were generated for all platforms. For the glucose assay, a solution of glucose oxidase (GOx), horseradish peroxidase, and potassium iodide was flowed through each platform and, upon contact with glucose, generated a yellow‐brown color indicative of the oxidation of iodide to iodine. For the protein assay, BSA was flowed through each device and, upon contact with citrate buffer and tetrabromophenol blue, resulted in a color change from yellow to blue. The devices were dried, scanned, and analyzed yielding a correlation between either yellow intensity and glucose concentration or cyan intensity and BSA concentration. A similar glucose assay, using unknown concentrations of glucose in artificial urine, was conducted and, when compared to the saturation curve, showed good correlation between the theoretical and actual concentrations (percent differences <10%). The development of 3D‐μPADs and 3D‐μTPADs can further facilitate the use of these platforms for colorimetric bioassays.
more » « less- NSF-PAR ID:
- 10462784
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- ELECTROPHORESIS
- Volume:
- 40
- Issue:
- 2
- ISSN:
- 0173-0835
- Page Range / eLocation ID:
- p. 296-303
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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