Method for detecting target particle

1. A method for detecting a target particle, comprising:

(a) preparing a pre-separation solution containing a target particle, a luminescent probe that binds to the target particle, and a particle for separation and recovery that is capable of being bound to a complex composed of the target particle and the luminescent probe, or containing the target particle bound to the luminescent probe, the luminescent probe and the particle for separation and recovery, and forming a complex comprising the target particle, the luminescent probe and the particle for separation and recovery in the solution,

(b) recovering the particle for separation and recovery from the pre-separation solution by solid-liquid separation treatment after (a), and preparing a sample solution containing the particles for separation and recovery, and

(c) calculating the number of the complex comprising the target particle, the luminescent probe and the particle for separation and recovery present in the sample solution prepared in (b), thereby detecting the target particle;

wherein the particle for separation and recovery binds to the complex composed of the target particle and the luminescent probe in (a),

wherein the calculating of the number of the complex comprising the target particle, the luminescent probe and the particle for separation and recovery in (c) is carried out by:

detecting light released from the complex comprising the target particle, the luminescent probe and the particle for separation and recovery in a photodetection region, while moving the location of the photodetection region of an optical system in the sample solution at a speed faster than the diffusion movement speed of the complex comprising the target particle, the luminescent probe and the particle for separation and recovery, using the optical system of a confocal microscope or multi-photon microscope, thereby obtaining a chronological light intensity data of the sample solution,

smoothing the chronological light intensity data,

individually detecting the complex comprising the target particle, the luminescent probe and the particle for separation and recovery from the detected light by individually detecting optical signals from individual complexes comprising the target particle, the luminescent probe and the particle for separation and recovery dispersed and randomly moving in the sample solution, based on a shape of smoothed chronological light intensity data, and

counting the number of target particles detected during movement of the location of the photodetection region by counting the number of individually detected complexes comprising the target particle, the luminescent probe and the particle for separation and recovery.

2. The method for detecting a target particle according to claim 1 , wherein the sedimentation rate of the particles for separation and recovery in the sample solution is 1×10 −6 m/s or less.

3. The method for detecting a target particle according to claim 1 , wherein, in the moving of the location of the photodetection region, the location of the photodetection region is moved along a second path over which the location thereof moves along a first path.

4. The method for detecting a target particle according to claim 3 , wherein the first and second paths are circulation paths, and a movement cycle of the location of the photodetection region along the second path is shorter than the movement cycle of the location of the second path along the first path.

5. The method for detecting a target particle according to claim 3 , wherein a movement cycle τ 1 of the location of the photodetection region, a movement speed v 2 of the location of the second path, and a diameter d of the photodetection region satisfy the following relational expression:

v 2·τ1> d.

6. The method for detecting a target particle according to claim 3 , wherein the location of the photodetection region moves along the second path by changing the light path of the optical system, and the location of the second path in the sample solution moves along the first path by moving the location of the sample solution.

7. The method for detecting a target particle according to claim 3 , wherein the second path is circular or elliptical, and the first path is circular, elliptical or linear.

8. The method for detecting a target particle according to claim 1 , wherein, in the individually detecting of the complex comprising the target particle, the luminescent probe and the particle for separation and recovery by individually detecting optical signals from individual complexes comprising the target particle, the luminescent probe and the particle for separation and recovery from the detected light, the entry of a single complex comprising the target particle, the luminescent probe and the particle for separation and recovery into the photodetection region is detected based on the form of a chronologically detected light signal.

9. The method for detecting a target particle according to claim 1 , wherein the particle for separation and recovery is a magnetic particle.