Method for detecting a target substance by using a nucleic acid probe

A method for collecting a target substance, comprising the steps of:

• forming a first complex comprising
• (a) a first nucleic acid probe immobilized on a first solid phase and having a single-strand portion,
• (b) a nucleic acid ligand which has a binding section hybridizable with the single-strand portion of the first nucleic acid probe and which has a target-binding substance capable of binding to the target substance,
• (c) the target substance, and
• (d) a labeling substance capable of binding to the target substance;
• separating, from the first complex, a second complex comprising the nucleic acid ligand, the target substance and the labeling substance;
• and
• collecting the separated second complex.

A reagent kit for detection of a target substance, comprising:

• a first solid phase on which a first nucleic acid probe having a single-strand portion is immobilized;
• a nucleic acid ligand having both a binding section hybridizable with the single-strand portion of the first nucleic acid probe and a target-binding substance capable of binding to the target substance;
• a second solid phase on which a second nucleic acid probe having a single-strand portion hybridizable with the binding section of the nucleic acid ligand is immobilized;
• and
• a labeling substance capable of binding to the target substance.