Method for detecting analyte and system for detecting analyte
A method for detecting an analyte includes first to third steps. The first step is distributing a sample containing a bead modified with a host molecule that is specifically bound to the analyte in a microchannel using a syringe pump. The second step is irradiating the sample with non-resonant light that is light outside a wavelength range of electronic resonance of the bead. The third step is detecting the analyte based on a signal from a camera that receives the light from the sample.
1 . A method for increasing a sensitivity of detection of an analyte, the method comprising:
pumping, by using a pump, a flow of a liquid sample through a microchannel, the flow of the liquid sample containing a plurality of fine particles each of which is modified with a host molecule that specifically binds to the analyte, the microchannel including an upper surface and a bottom surface, and the microchannel being filled with the flow of the liquid sample;
irradiating the liquid sample flowing through the microchannel with non-resonant light outside a wavelength range of electronic resonance of the plurality of fine particles such that an aggregate of the analyte and the plurality of the fine particles is formed, the irradiating including:
irradiating the liquid sample with the non-resonant light under a condition that a focal point of the non-resonant light is located further behind the upper surface or the bottom surface of the microchannel, the focal point located behind the microchannel in an irradiation direction of the non-resonant light; and
applying a force induced by the non-resonant light in a same direction as the irradiation direction to press the plurality of fine particles against the upper surface or the bottom surface behind which the focal point is located;
capturing, via an optical receiver that receives light from the liquid sample, an image of the liquid sample;
image-processing the image of the liquid sample, thereby determining a size of an aggregate formed by aggregation of the analyte and the plurality of fine particles contained within the liquid sample; and
detecting a concentration of the analyte contained in the liquid sample based on the size of the aggregate and a previously-obtained correspondence relationship between concentrations of the analyte and sizes of aggregates.
2 . The method for increasing the sensitivity of detection of the analyte according to claim 1 , wherein:
the optical receiver includes a camera that captures the image of the liquid sample;
the image-processing includes calculating, based on the image, an index representing the size of the aggregate; and
the detecting includes calculating, by referring to the previously-obtained correspondence relationship, the concentration of the analyte contained in the liquid sample based on the calculated index.
3 . The method for increasing the sensitivity of detection of the analyte according to claim 1 , further comprising stopping the irradiation with the non-resonant light after the irradiating, and wherein:
the detecting includes detecting the concentration of the analyte based on a signal acquired from the optical receiver after standby for a period of time required to wash the aggregate formed within the flow of the liquid sample after the irradiation with the non-resonant light is stopped, and
washing the aggregate includes sweeping away, from the aggregate, fine particles which are not bound to the aggregate in a flow direction of the liquid sample.
4 . The method for increasing the sensitivity of detection of the analyte according to claim 1 , wherein the detecting includes determining whether the analyte is contained in the liquid sample based on a change in intensity of a signal acquired from the optical receiver while the irradiating with the non-resonant light is continued.
5 . The method for increasing the sensitivity of detection of the analyte according to claim 1 , wherein:
specific gravity of each of the plurality of fine particles is larger than specific gravity of a dispersion medium of the plurality of fine particles, and
the irradiating includes irradiating the liquid sample with the non-resonant light from above to below of the liquid sample.
6 . The method for increasing the sensitivity of detection of the analyte according to claim 1 , wherein the irradiating includes irradiating the liquid sample with the non-resonant light so that a region of the microchannel through which the liquid sample flows is not irradiated with the non-resonant light.
7 . The method for increasing the sensitivity of detection of the analyte according to claim 1 , further comprising, prior to the irradiating, adjusting a flow velocity of the liquid sample to a flow velocity at which the analyte and the plurality of fine particles can be prevented from splitting after aggregation.
8 . The method for increasing the sensitivity of detection of the analyte according to claim 1 , wherein at least one of the analyte or the plurality of fine particles is modified with a fluorescent dye.
9 . The method for increasing the sensitivity of detection of the analyte according to claim 1 , wherein a combination of diameters of the plurality of fine particles and a wavelength range of the non-resonant light is determined such that the non-resonant light causes Mie scattering when the plurality of fine particles are irradiated with the non-resonant light.