Determination of human IgG by solid substrate room temperature phosphorescence immunoassay based on an antibody labeled with nanoparticles containing dibromofluorescein luminescent molecules

Luminescent silicon dioxide nano-particles with size of 20 nm, which containing dibromofluorescein (D) were synthesized by sol-gel method (symbolized by D-SiO2).The particles can emit intense and stable room temperature phosphorescence signal on polyamide membrane when Pb(Ac)2 was used as a heavy atom perturber. The λexmax/λemmax was 457/622 nm. Our research indicated that the specific immune reaction between goat-anti-human IgG antibody labeled with D-SiO2 and human IgG could be carried out on polyamide membrane quantitatively, and the phosphorescence intensity of the particle was enhanced after the immunoreactions. Thus a new method of solid substrate room temperature phosphorescence immunoassay (SS-RTP-IA) for the determination of human IgG was established basing on antibody labeled with the D-SiO2 nanoparticles. The linear range of this method was 0.0624-20.0 pg human IgG spot−1 (corresponding concentration: 0.156-50.0 ng ml−1, the sample volume: 0.40 μl spot−1) with a limit of detection (LD) as 0.018 pg spot−1, and the regression equation of working curve was ΔIp = 7.201 mIgG (pg spot−1) + 82.57. Samples containing 0.156 and 50.0 ng ml−1 of IgG were measured repeatedly for 11 times and R.S.D.s were 4.1 and 3.4%, respectively. Results showed that this method had the merits as sensitive, accurate and precise.