Abstract: A method for detecting a target nucleic acid fragment in a sample includes a step of contacting the sample with a gRNA complementary to the target nucleic acid fragment, a Cas protein, and a substrate nucleic acid fragment, in which the Cas protein is immobilized on a solid phase, a substrate nucleic acid fragment is labeled with a fluorescent substance and a quencher, in a case of being cleaved by nuclease activity of a three-part complex of the Cas protein, the gRNA, and the target nucleic acid fragment, fluorescent light is emitted, the contact is performed in a reaction space having a volume of 10 aL to 100 pL, thereby forming the three-part complex in a case where the target nucleic acid fragment is present in the sample, cleaving the substrate nucleic acid fragment, and separating the fluorescent substance from the quencher; and detecting the fluorescent light, in which the detection of the fluorescent light indicates the presence of the target nucleic acid fragment in the sample.

Abstract: A method for detecting a target substance in a sample includes a step of introducing the sample and a reagent that generates a fluorescent substance in a presence of the target substance into each well of a well array; a step of sealing each well of the well array with a sealing liquid such that each well forms an independent reaction space; a step of replacing the sealing liquid with a water-absorbing organic solvent, thereby dehydrating the content of the well, reducing the volume, and generating the fluorescent substance in a case where the target substance is present in the content; and a step of emitting excitation light to the fluorescent substance to detect fluorescent light generated in each well of the well array, in which detection of the fluorescent light in the well indicates the presence of the target substance in the well.