A study published in Systems Microbiology and Biomanufacturing has described a paper-based diagnostic device designed to rapidly detect miRNA-21, a microRNA commonly associated with cancer.
MicroRNAs are increasingly being studied as potential non-invasive biomarkers because they can reflect changes linked to tumor development and progression. However, detecting them reliably remains difficult because they are present at very low levels in blood and have short, highly similar sequences.
To address this challenge, researchers developed a microfluidic paper-based analytical device (µPAD) that combines paper-based testing with nanoparticle-driven colorimetric detection. The assay uses gold-platinum nanoparticles that trigger a visible color change when miRNA-21 is present.
The test works by allowing the target miRNA to bind to complementary DNA on the device. This reaction releases nanoparticle conjugates, which move through the paper strip by capillary action. In the detection zone, the nanoparticles catalyze a reaction that changes the test area from colorless to blue. The signal can then be quantified using a smartphone image and ImageJ software.
Under optimized laboratory conditions, the device demonstrated a detection range of 1–2000 nmol/L and a detection limit of 0.25 nmol/L. The researchers also reported successful detection of miRNA-21 in spiked human serum samples.
Current molecular testing for cancer biomarkers often requires specialized instrumentation, centralized laboratories, and longer turnaround times. Paper-based microfluidic systems could eventually support faster, lower-cost testing in settings with limited laboratory infrastructure.
The study also highlights continued interest in point-of-care molecular diagnostics that can be paired with simple imaging tools such as smartphones. While the assay remains experimental and would require substantial clinical validation before routine use, it reflects broader efforts to make molecular biomarker testing more accessible and scalable across clinical settings.
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