| abstract |
[Problem] To provide a means for, in Immunostaining using fluorescent nano particles, preventing the occurrence of non-specific adsorption of the fluorescent nano particles to reduce background noises, thereby detecting and quantifying a biological substance of interest with higher accuracy, [Solution] Immunostaining is carried out by diluting fluorescent nano particles with a diluent for fluorescent nano particles, wherein the diluent for fluorescent nano particles contains 1 to 5% (W/W) of a protein having a molecular weight of 40,000 or more (e.g., BSA) and 1 to 3% (W/W) of a protein having a molecular weight of less than 40,000 (e.g., casein). In the diluent, when casein is used as the low-molecular-weight protein, it is preferred that the content of κ-casein in the casein is 10% (W/W) or less and the ratio of the content of α-casein to the content of β-casein, i.e., an α-casein:β-casein ratio, is (40 to 60):(60 to 40) (wherein the total amount of α-casein and β-casein is 100). |