Mini review: Recent progress in RT-LAMP enabled COVID-19 detection

Abstract

The coronavirus disease 2019 (COVID-19) pandemic has infected millions of people around the globe. The outbreak caused by the novel coronavirus (SARS-CoV-2) poses a great health risk to the public. Therefore, rapid and accurate diagnosis of the virus plays a crucial role in treatment of the disease and saving lives. The current standard method for coronavirus detection is the reverse transcription polymerase chain reaction (RT-PCR) method. However, laboratory-based RT-PCR test for SARS-COV-2 requires complex facilities and elaborate training of operators, thus suffering from limit testing capacity and delayed results. Consequently, isothermal PCR such as loop-mediated isothermal amplification (LAMP) has been emerging as a great alternative to the RT-PCR method. LAMP possesses some fundamental advantages such as amplification at a constant temperature, exclusion of a thermal cycler, a faster test result, and potentially a larger diagnostic capacity, while maintaining similar sensitivity and specificity, thus making it more suitable than the RT-PCR for monitoring a pandemic. Starting with a brief introduction of the working principle of LAMP method, this review summarizes recent progress in LAMP-enabled SARS-CoV-2 viral RNA detection. Lastly, future research directions are discussed. This critical review will motivate biosensor community in furthering the present research, which may pave the road for rapid and large-scale screening of SARS-CoV-2.

Keywords: COVID-19; Isothermal amplification; Molecular diagnosis; RT-LAMP; Rapid.

Fig. 1

Schematic drawing of the LAMP amplification process . Arrowing from the primer signifies direction of DNA synthesis. The desired sequence for amplification is shown in dark red. A. Initial steps to form dumbbell-like structure. B. Cyclic amplification of LAMP. (Reprinted from ref. 9).

Fig. 2

Sensitivity test for COVID-19 simulated samples. All readout methods are presented (top to bottom: color change, fluorescence under UV light, gel electrophoresis). (Reprinted from ref. 7).

Fig. 3

Readout signal of COVID-19 samples with GeneFinder dye under blue light. Left are negative controls and right are positive samples. (Reprinted from ref. 14).

Fig. 4

Sensitivity results for mismatch-tolerant RT-LAMP process. (Reprinted from ref. 16).

Fig. 5

Barcoding concept for LAMP-Seq procedure. (Reprinted from ref. 5).

Fig. 6

Diagram of purification protocol, with colorimetric readout. A) Testing without purification B) Purification from swab sample C) Purification from saliva sample. (Reprinted from ref. 17).

Fig. 7

Visual detection after Penn-LAMP (A) and schematic drawing of Penn-RAMP process (B). (Reprinted from ref. 6).

Fig. 8

Diagram of RT-LAMP and CRISPR-Cas12 based COVID-19 detection. (Reprinted from ref. 2).

Fig. 9

Illustration of the FAM-biotin reporter used in SARS-CoV-2 DNA Endonuclease-Targeted CRISPR Trans Reporter (DETECTR) in conjunction with lateral flow detection platform . When not cleaved, the reporter will bind to the control line in the LFA, confirming the absence of the target gene. (Reprinted from ref. 2).

Fig. 10

The overview of STOPCovid method. (Reprinted from ref. 18).