An aptamer nanoprobe (AptAu) for thrombin was prepared using the nanogold labeled aptamer. In pH 7.4 Na₂HPO₄-NaH₂PO₄ buffer solution and in the presence of NaCl and KCl, the analyte of thrombin reacted with AptAu to form stable G-quartet and release nanogold particles that aggregated to big clusters. After filtration by microporous filter membrane, the big clusters were removed and filtrated solution containing AptAu was obtained. That exhibited catalytic effect on the slow gold particle reaction between HAuCl₄ and VC at 60 ℃. There is a resonance scattering peak at 600 nm. With the increasing concentration of thrombin, the AptAu content in the filtrated solution decreased, and the resonance scattering intensity at 600 nm decreased. The decreased RS intensity is linear to thrombin concentration in the range from 6.40×10^－3 U/mL to 0.150 U/mL, with a regression equation of ΔI＝1.26×10³C＋1.50 and a detection limit of 1.30×10^－3 U/mL. The method was used for quantitative analysis of thrombin in human plasma with satisfactory results.

Key words: thrombin, aptamer, nanogold catalysis, resonance scattering spectral assay