End-point dual specific detection of nucleic acids using CRISPR/Cas12a based portable biosensor.

A CRISPR/Cas12a based portable biosensor (Cas12a-PB) was developed to simultaneously visually detect CaMV35S promoter and Lectin gene from genetically modified (GM) soybean powders (Roundup Ready@). The Cas12a-PB, mainly made of polymethylmethacrylate (PMMA) and PMMA tape, has a connection structure, three channels and three detection chambers. The CRISPR/Cas12a detection reagents were preloaded in detection chambers and the reaction tube was connected to the connection structure by screw threads. After amplification, the amplicons were gone into three detection chambers by swinging the Cas12a-PB to conduct dual detection. Positive samples would produce green fluorescence while negative samples were black under the irradiation of 490 nm LED light. In this study, the Cas12a-PB successively combined with ordinary PCR, rapid PCR and loop-mediated isothermal amplification (LAMP) to achieve dual detection, which made detection process more convenient and portable. As low as 0.1% transgenic ingredients in soybean powders could be detected and the specificity of Cas12a-PB was confirmed with GM maize powders (MON810, GA21), GM soybean powders (DP305423), non-GM peanut and rice as targets. In the end, an amplification chamber combining with Cas12a-PB on a PMMA chip was further designed to eliminate the use of reaction tube and mineral oil, which made operation simpler. The established Cas12a-PB would provide a new reliable solution for multiple targets detection in clinic diagnostics, food safety, etc.