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Though qPCR remains the gold standard for the diagnosis of SARS-CoV-2, loop mediated isothermal amplification (LAMP) assays have been demonstrated to produce diagnostic results with increased sensitivity and specificity. Further, its ability to tolerate PCR inhibitors eliminates the need for laborious RNA extraction and purification methodologies. Several platforms capable of performing LAMP assays in the field of diagnostics have been demonstrated in the past. However, most platforms employed fluorescence detection with integrated optical units or a smartphone dock to achieve detection. Similarly, for colorimetric LAMP assays, smartphone cameras or user interpretation of the colour change was used to achieve detection. The fully integrated real-time fluorescence-based platforms were expensive, and the smartphone-based platforms were only designed for specific smartphone models. Therefore, to fulfil the need for a standalone colorimetric isothermal nucleic acid amplification platform, we have developed an ultra-low-cost molecular diagnostic device with an integrated single-board computer, imaging camera, artificial intelligence-based image processing algorithm and mobile app.

During the early stages of the lock-down period in April, a consortium of academics from СʪÃÃÊÓƵ London, University of Lancaster and the University of Surrey has been working on a Newton Fund grant administered by the BBSRC to develop a low-cost, handheld, rapid detection device for molecular detection of poultry pathogens for in farm use in the Philippines. The technique employed in the device was colorimetric AI-LAMP. It was collectively decided to repurpose the project to produce devices for detecting SARS-CoV-2. In the middle of April, a team led by Professor Balachandran of СʪÃÃÊÓƵ London rapidly assembled 10 devices to perform preliminary tests of SARS-CoV-2 using the CL3 laboratories in Lancaster and Surrey. These devices are shown in Figure 1.

These prototype devices were built with many off-the-shelf electronic components and custom flexible resistive heating elements and specially designed aluminium heating blocks. Raspberry Pi (RPi) was used to control the device. The Python-based control software was used to control the heating, the image progression of the LAMP assay and store the ‘time-lapse’ images and temperature data within a specified folder. The user can initiate a test by either connecting to a screen via the HDMI port or by simply pairing the device with the mobile app via Bluetooth and selecting the required diagnostic assay. We are also developing a novel sample preparation cartridge for easy extraction of RNA from swab samples.

Industrial Collaboration: Based on this successful outcome we partnered with Vidiia Ltd () to manufacture devices with improved firmware and software to comply with CE marking criteria stipulated by regulatory bodies. The company has improved the ergonomics of the existing prototype to enhance functionality and safety features. The CAD has been optimized to incorporate additional features; including thermal management and design for manufacturing principles. The device manufactured by Viddia is called “Virus Hunter 6 - VH⁶” and is shown in Figure 2. It includes a communication module to enable it to communicate via a mobile network. Further improvement of the AI-based image processing algorithm was also implemented on VH6.

The device (VH6) can be used to obtain SARS-CoV-2 test results quickly and with great ease. Test preparation is simple and fast. Test preparation time is under 10 minutes including swab collection, the RT-LAMP assay takes 20 minutes to reach endpoint result, and total test time is therefore 30 minutes. It works by linking a test kit to a test device along with the use of a smart device app for android or iOS. The smart app registers patients for swab collection and managers the entire process, thus ensuring tests are traced and secure. The smart test app also walks the operator through the test at every stage. The VH6 can run up to six individual tests simultaneously. The results are interpreted by the in-built camera and AI algorithms and displayed through Vidiia’s innovative smart app. The VH6 has been CE IVD and MHRA registered, and ready for commercialisation.