Diagnosing pathogen infection at the point-of-care in resource limited settings with on-chip integrated workflows

Populations in many lower- and lower-middle income countries are plagued by endemic and emerging infectious diseases which continue to be a major health burden, hindering sustainable development and bringing suffering often to the poorest of the population. Existing diagnostic approaches are generally too costly or do not function in the challenging settings of regional and rural health clinics. The WHO has put forward requirements for point-of-care diagnostics (PoCD) as needing to be Affordable, Sensitive, Specific, User-friendly, Rapid and robust, Equipment-free and Deliverable to end-users (ASSURED). The more recent addition of Real-time connectivity and Ease of specimen collection has led to the coining of the acronym REASSURED. In this context, we have been developing on-chip workflows for integrated nucleic-acid based pathogen diagnostics that can be operated in low-resource environments. The cartridges features adjacent chambers, that are connected by micrometer dimension gates. The operation of the devices is based on the surface tension between immiscible aqueous and oil phases filled into the chambers, and the transport of functionalised paramagnetic particles (PMPs) through the water/oil interfaces. Cell lysis and nucleic acid capture on the PMPs is performed in the first chamber. The particles are then pulled manually by an external permanent magnet through a series of oil/water gates to undergo washing and then nucleic acid amplification, usually via colorimetric loop-mediated isothermal amplification (LAMP) or CRISPR-Cas12a-assisted detection with lateral flow test readout. We have applied this concept to the detection of Neisseria gonorrhoeae, Chlamydia trachomatis, SARS-CoV2 RNA and, more recently the soil infecting fungus Sclerotium rolfsii. All operations are performed in a single cartridge that requires simple operation steps and basic equipment and offer great potential for multiplexing and portability.