A robust, low-cost instrument for real-time colorimetric isothermal nucleic acid amplification

Portable loop-mediated isothermal amplification device with spectrometric detection for rapid pathogen identification

With the rise in extreme weather due to global warming, coupled with globalization facilitating the spread of infectious diseases, there's a pressing need for portable testing platforms offering simplicity, low cost, and remote transmission, particularly beneficial in resource-limited and non-urban areas. We have developed a portable device using loop-mediated isothermal amplification (LAMP) with spectrometric detection to identify Salmonella Typhimurium DNA. The device utilizes the LinkIt 7697 microcontroller and a microspectrometer to capture and transmit spectral signals in real-time, allowing for improved monitoring and analysis of the reaction progress. We built a hand-held box containing a microspectrometer, thermoelectric cooler, ultraviolet LED, disposable reaction tube, and homemade thermal module, all powered by rechargeable batteries. Additionally, we conducted thorough experiments to ensure temperature accuracy within 1 °C under thermal control, developed a heating module with a LinkIt 7697 IoT development board to heat the DNA mixture to the reaction temperature within 3 min, and integrated foam insulation and a 3D-printed frame to enhance the device's thermal stability. We successfully demonstrated the amplification of Salmonella Typhimurium DNA with an impressive sensitivity of 2.83 × 10-4 ng/μL. A remote webpage interface allows for monitoring the temperature and fluorescence during the LAMP process, improving usability. This portable LAMP device with real-time detection offers a cost-effective solution for detecting Salmonella Typhimurium in food products. Its unique design and capabilities make it a promising tool for ensuring food safety.

Robust and low-cost open-source device for detecting infectious microorganisms by loop-mediated isothermal amplification

Loop-Mediated Isothermal Amplification (LAMP) is a useful technique for detecting infectious microorganisms in human fluids since it performs similarly to conventional PCR, the results are obtained faster and no thermocyclers or complex devices are required. Since only two isothermal blocks (95 °C to lyse cells and 65 °C for DNA amplification) are needed, LAMP is particularly suited for applications in Low- and Middle-Income Countries (LMICs). To validate such assumption, we first designed and tested Arduino-controlled LAMP thermoblocks to process a considerable number of samples simultaneously with a low-energy consumption to enable routine use under worst-case conditions (no main power source and low ambient temperatures). The thermoblocks were tested when battery-powered at temperature down to 5 °C, showing high stability in well temperatures (<0.8 °C). The charge required for both thermoblocks to simultaneously achieve the target temperatures after switching on and to keep their working temperatures were 4.1 A·h and 2.4 A·h/h, respectively. Second, we implemented a low-cost viewer with LEDs and filters to detect the fluorescent LAMP reaction. All the components required for the instrument are for general purpose and readily available by e-commerce. Thus, the LAMP device allows for considerable autonomy by using a typical car battery in rural and itinerant healthcare or field hospitals in LMICs, even under difficult environmental conditions.

At-home testing for respiratory viruses: a minireview of the current landscape

The landscape of at-home testing using over-the-counter (OTC) tests has been evolving over the last decade. The United States Food and Drug Administration Emergency Use Authorization rule has been in effect since the early 2000s, and it was widely employed during the severe acute respiratory syndrome coronavirus 2 pandemic to authorize antigen and nucleic acid detection tests for use in central laboratories as well as OTC. During the pandemic, the first at-home tests for respiratory viruses became available for consumer use, which opened the door for additional respiratory virus OTC tests. Concerns may exist regarding the public's ability to properly collect samples, perform testing, interpret results, and report results to public health authorities. However, favorable comparison studies between OTC testing and centralized laboratory test results suggest that OTC testing may have a place in healthcare, and it is likely here to stay. This mini-review of OTC tests for viral respiratory diseases will briefly cover the regulatory and reimbursement environment, current OTC test availability, as well as the advantages and limitations of OTC tests.

Three-Dimensional-Printed Instrument for Isothermal Nucleic Acid Amplification with Real-Time Colorimetric Imaging

Isothermal amplification methods have become popular in research due to the simplicity of the technology needed to run the reactions. Specifically, loop-mediated isothermal amplification (LAMP) has been widely used for various applications since first reported in 2000. LAMP reactions are commonly monitored with the use of colorimetry. Although color changes associated with positive amplification are apparent to the naked eye, this detection method is subjective due to inherent differences in visual perception from person to person. The objectivity of the colorimetric detection method may be improved by programmed image capture over time with simultaneous heating. As such, the development of a novel, one-step, automated, and integrated analysis system capable of performing these tasks in parallel is detailed herein. The device is adaptable to multiple colorimetric dyes, cost-effective, 3D-printed for single-temperature convective heating, and features an easy-to-use LabVIEW software program developed for automated image analysis. The device was optimized and subsequently validated using four messenger-RNA targets and mock forensic samples. The performance of our device was determined to be comparable to that of a conventional thermal cycler and smartphone image analysis, respectively. Moreover, the outlined system is capable of objective colorimetric analysis, with exceptional throughput of up to 96 samples at once.