Novel Platform for Easy and Accurate Diagnosis of Infectious Diseases

A new one-step device is developed to quantitatively detect target pathogens

Accurate diagnosis of infectious diseases is critical in minimizing pathogen-associated deaths and further spread of the disease. Through a novel automated platform, Haowen Yang and collaborators have demonstrated rapid and quantitative detection of Mycobacterium tuberculosis (MTB), the bacterium responsible for tuberculosis.

Although current technologies can detect the presence of pathogens in human samples, most devices only provide qualitative diagnosis—an approach insufficient for determining infection severity and monitoring treatment efficacy. On the other hand, available quantitative tests are limited by sophisticated instruments, the need for skilled staff, and long turnaround times. Accordingly, Haowen has developed a new microfluidic system that uses a digital nucleic acid amplification test (NAAT) to quantify MTB from human saliva and blood serum. The device consists of a cartridge and microfluidic device both held within a customized instrument. The only manual step required within the entire diagnostic process is sample addition into the cartridge. The instrument then automates the pipetting, sample preparation, and signal readout of the NAAT, which happens within the microfluidic chip.

A key ingenuity lies in the assay procedure. To perform digital NAATs, the reaction mixture must first be partitioned into thousands of distinct microwells. Haowen implemented a novel mechanical pressure-sealing technique to compress the microfluidic device and force the reaction mixture into the microwells [Figure 1a,b]. This facile method obviates the need for complex valves and multilayer devices commonly used in conventional microfluidic devices, overcoming significant challenges in systems engineering and cost management. The NAAT can then proceed and absolute quantification of MTB DNA is determined by the number of microwells exhibiting fluorescence [Figure 1c].

The novel platform was applied to human samples spiked with known amounts of MTB and high recovery rates were obtained (90% in saliva and 80% in blood serum). The results verify the system’s accuracy, demonstrating its promise as an easy-to-use quantitative diagnostic tool.

Written by Jeff Hsiao.

Read the full paper here.

Figure 1. Schematic of the microfluidic device (a) prior to and (b) after mechanical pressure sealing. (c) Fluorescent microwells for quantitative detection.

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