Microfluidic-based colorimetric nucleic acid detection of pathogens

Infectious diseases caused by pathogens put a significant burden on global health, as exemplified by the COVID-19 pandemic. There is a need for cost-effective detection techniques that ensure high sensitivity and specificity, comparable to standard methods. Point-of-care (POC) nucleic acid detection techniques provide low-cost, rapid solutions for congregate and remote settings. Microfluidic devices combined with colorimetric read-outs, as one of the portable and easy-to-interpret detection techniques, are apt for POC diagnostics. This paper reviews the most recent advances in colorimetric-based microfluidic devices for the nucleic-acid detection of viruses, bacteria, fungi, and protozoa including influenza, SARS-CoV-2, Listeria, Pseudomonas, Candida, and malaria. The characteristic features of devices, effectiveness of pathogen detection, analysis time, sensitivity and specificity of the results are discussed here. In addition, this paper offers an insight on the future avenues of microfluidic-based colorimetric detection, highlighting the necessary steps for achieving the high caliber set by gold standard techniques. This article suggests that the integration of plasmonic nanostructures with microfluidic devices will address the issue of sensitivity in today's colorimetric-based devices. Future work should also focus on addressing the need for an all-encompassing device, as well as the commercialization of devices to augment translation in clinical settings. In this review, we highlight the most recent advances in the nucleic acid detection of viruses, bacteria, fungi, and protozoa in a portable fashion using colorimetric-based microfluidic devices.