A morphology-based ultrasensitive multicolor colorimetric assay for detection of blood glucose by enzymatic etching of plasmonic gold nanobipyramids.

An ultrasensitively multicolor colorimetric assay on the basis of enzyme-catalyzed reaction mediated etching of gold nanobipyramids (Au NBPs) is developed for detection of blood glucose with naked eye. This assay depends on the catalytic oxidation of H2O2 (generated from glucose oxidation) by horseradish peroxidase (HRP) to generate hydroxyl radicals (•OH) with strong oxidizability, which can accelerate the Au NBPs etching and accompany with vivid color changes and localized surface plasmon resonance (LSPR) blue shift. On the basis of this, the proposed colorimetric glucose assay accomplishes a dynamic range of 0.05-90 μM with detection limit of 0.02 μM, which is almost three orders of magnitude lower than that (10 μM) based on gold nanorods (Au NRs). Moreover, the approximate glucose levels can be intuitively and conveniently judged by the color changes with naked eye. Most importantly, visually distinguish between healthy people and diabetic patients by naked eye dispense with any sophisticated instrument is the most important highlight of this colorimetric assay, indicating the available potential for diagnosis. To the best of our knowledge, this is the first report of colorimetric assay using Au NBPs as etching substrates for visually analysis of glucose.