A solid-state heater-imager for quantitative evaluation of colorimetric isothermal nucleic acid amplification on paper.
basic_science · Level V
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- Record sourced from PubMed, PMID 42578606.
- Also identified by DOI 10.1039/d6lc00154h.
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Abstract
Maintaining precise isothermal conditions in portable nucleic acid amplification tests (NAATs) is critical for reproducible results but remains challenging with conventional single-sided thin-film heaters, which exhibit temperature gradients and strong dependence on ambient conditions. To close this gap, we engineered ThermiQuant™ VitroMini, a dual-sided heater design that achieves volumetric-level temperature uniformity using thin-film heaters while preserving optical transparency for real-time colorimetric loop-mediated isothermal amplification (LAMP) analysis on microfluidic paper-based analytical devices (μPADs). The device integrates two independently regulated indium tin oxide (ITO) heaters (8 Ω each) controlled by independent proportional-integral-derivative (PID) algorithms. Heaters were evaluated under controlled ambient environments of 4 °C (refrigerated), 23 °C (room temperature), and 50 °C (oven). Analytical tests were performed using a colorimetric LAMP assay targeting the SARS-CoV-2 <i>orf7ab</i> gene on μPADs preloaded with dried LAMP reagents, with time-lapse images (30 seconds interval) analyzed <i>via</i> Amplimetrics™ software. VitroMini maintained 65 ± 0.5 °C across 4 to 50 °C ambient conditions and achieved a limit of detection of 34 copies per reaction (4.5 copies per μL) and limit of quantification of 1000 copies per reaction (133 copies per μL), with quantification time (<i>T</i><sub>q</sub>) linearly correlated with log<sub>10</sub> DNA concentration. Dual-sided heating eliminated temperature bias, condensation artifacts, and ambient-dependent variability while preserving optical transparency for real-time quantitative LAMP reaction. ThermiQuant™ VitroMini bridges the gap between benchtop volumetric heaters and portable diagnostic devices, offering a compact, low-power platform for quantitative colorimetric molecular analysis on paper with potential for decentralized and field-deployable applications.