Development and application of a universal extraction-free reagent based on an algal glycolipid

In this study, we independently developed a universal nasopharyngeal swab extraction-free reagent based on a trehalose lipid for the rapid detection of pathogen nucleic acids in respiratory infectious diseases. By comparing the isothermal amplification results of a 2019-nCoV pseudovirus solution treated with different components of the extraction-free reagent, we determined the optimal composition of the extraction-free reagent to be a mixed solution of 10 mmol L^-1 tris-HCl containing 0.05 mmol L^-1 EDTA (TE solution), 5% glycine betaine, 0.5% Triton X-100, and 1.5% trehalose lipid. The results showed that the extraction-free reagent could cleave DNA viruses, RNA viruses, and bacteria to release nucleic acids and did not affect the subsequent nucleic acid amplification. Its efficiency was consistent with that of magnetic bead extraction. Real-time fluorescence quantitative PCR was used to analyze the stability and repeatability of the detection results of the samples treated with the extraction-free reagent and the sensitivity of the extraction-free reagent. The results showed that the extraction-free kit could stably store the pathogen nucleic acid for at least 24 hours, the detection repeatability was satisfactory, and there was no incompatibility with the detection limits of various manufacturers' nucleic acid detection reagents. In conclusion, the established nucleic acid extraction-free method can effectively lyse respiratory infectious disease pathogens to release nucleic acids (DNA and RNA) at room temperature and can directly amplify nucleic acids without extraction steps. This method takes a short time and has high efficiency. The released nucleic acid met the requirements of molecular biological detection methods such as real-time fluorescence quantitative PCR (qPCR), reverse transcription-polymerase chain reaction (RT-PCR), and isothermal nucleic acid amplification (INAA).