Magnetic Bead Handling Using a Paper-Based Device for Quantitative Point-of-Care Testing.

Area of Science:

• Analytical Chemistry
• Biomedical Engineering
• Point-of-Care Diagnostics

Background:

• Microfluidic paper-based analytical devices (μPADs) offer potential for point-of-care (POC) testing.
• Existing μPADs often rely on dried reagents, leading to production, stability, and storage challenges.
• Room temperature storage and simplified manufacturing are critical for widespread POC adoption.

Purpose of the Study:

• To develop an affordable, room-temperature-storable μPAD for partially automating magneto-immunoassays.
• To demonstrate the μPAD's utility for quantitative detection of Plasmodium falciparum lactate dehydrogenase (Pf-LDH), a malaria biomarker.
• To assess the device's performance against established diagnostic methods.

Main Methods:

• Fabrication of μPADs using a craft cutter for affordability and ease of production.
• Implementation of a single-step colorimetric magneto-immunoassay involving magnetic beads (MB), antibodies, and an enzymatic amplifier.
• On-chip magnetic concentration and washing of MBs, followed by colorimetric signal generation and readout via naked eye or smartphone imaging.

Main Results:

• Quantitative detection of Pf-LDH achieved in under 15 minutes.
• Detection limits of 6.25 ng mL−1 (naked eye) and 1.4 ng mL−1 (smartphone imaging).
• Clinical sample analysis showed correlation with ELISA and superior sensitivity compared to commercial rapid diagnostic tests (RDTs).

Conclusions:

• The developed μPAD enables partial automation of magneto-immunoassays, meeting key requirements for POC testing.
• The device offers a stable, room-temperature-storable, and affordable platform for malaria diagnosis.
• This approach significantly enhances the potential of μPADs for accessible and sensitive disease detection.