Fully integrated microfluidic devices for qualitative, quantitative and digital nucleic acids testing at point of care

Abstract

Benefiting from emerging miniaturized and equipment-free nucleic acid testing (NAT) technologies, fully integrated NAT devices at point of care (POC) with the capability of "sample-in-answer-out" are proceeding at a break-neck speed to eliminate complex operations and reduce the risk of contamination. Like the development of polymerase chain reaction (PCR) technology (the standard technique for NAT), the detection signal of fully integrated NAT devices has evolved from qualitative to quantitative and recently to digital readout, aiming at expanding their extensive applications through gradually improving detection sensitivity and accuracy. This review firstly introduces the existing commercial products, and then illustrates recent fully integrated microfluidic devices for NAT at POC from the aspect of detection signals (i.e., qualitative, quantitative and digital). Importantly, the key issues of existing commercial products and the main challenges between scientific research and product development are discussed. On this basis, we envision that the MARCHED (miniaturized, automatic, reagent-preloaded, commercializable, high-throughput, environment-independent and disposable) NAT devices are expected to be realized in the near future.

Keywords: Commercial products; Digital amplification; Isothermal amplification; Microfluidic chips; Paper microfluidics; Sample preparation.

Fig. 1

Development of fully integrated microfluidic devices for nucleic acids testing at point of care.

Fig. 2

Fully integrated commercial microfluidic devices for detection of nucleic acids. (a) GeneXpert® system developed by Cepheid. (b) Filmarray® developed by Biofire. (c) Cobis Liat® developed by Roche. (d) ID NOW® developed by Abbott. (e) COVID-19 all-in-one test kit® delivered by Lucira Health.

Fig. 3

Fully integrated microfluidic devices for qualitative detection of nucleic acids. (a) A fully integrated paper chip for EGFR mutation detection. (b) An integrated centrifugal microfluidic disc for multiple targets detection. (c) A “Paper Machine” for Escherichia coli detection. (d) A micro-pipette tip-based NAT in crude samples. Images reproduced from (Chen et al., 2019; Connelly et al., 2015; Lu et al., 2016; Oh et al., 2016).

Fig. 4

Fully integrated microfluidic devices for quantitative detection of nucleic acids. (a) An integrated electrochemical chip for NA detection. (b) A paper-based integrated NAT device based on combination of ITP and RPA. (c) A miniaturized 3D printed battery-operated reactor composed of a portable heater module and a USB fluorescence microscope for chip analysis. (d) An integrated chip for viable Salmonella detection based on real-time turbidity LAMP monitoring. Images reproduced from (Bender et al., 2018; Kadimisetty et al., 2018; Koo et al., 2018; Wang et al., 2020).

Fig. 5

Fully integrated microfluidic devices for digital detection of nucleic acids. (a) Self-powered integrated microfluidic point-of-care low-cost enabling (SIMPLE) chip for detecting DNA directly from human plasma. (b) A “sample-in-multiplex-digital-answer-out” chip for fast detection of pathogens. (c) An integrated droplet-based digital LAMP device based on smartphone imaging and analyzing. (d) An integrated droplet-based digital PCR device for ctDNA detection. Images reproduced from (Geng et al., 2020; Hu et al., 2019; Yeh et al., 2017; Yin et al., 2020).

Fig. 6

Future perspectives of integrated microfluidic devices for nucleic acids testing at point of care.