Colorimetric and fluorometric aggregation-based heparin assay by using gold nanoclusters and gold nanoparticles.

Abstract

An optical nanoprobe consisting of gold nanoclusters (AuNCs) and gold nanoparticles (AuNPs) is described for ultrasensitive detection of heparin (Hep). Polyethyleneimine (PEI) induces the aggregation of AuNPs which results in a color change from wine red (peak at 520nm) to blue (peak at 610nm). In parallel, the fluorescence of AuNCs (with excitation/emission maxima at 370/610nm) is weakened. However, in the presence of Hep (which is strongly negatively charged), it will electrostatically bind to positively charged PEI and then will prevent aggregation. Hence, the color changes from blue (aggregated) to red (non-aggregated). In parallel, fluorescence remains unchanged. Hep can be quantified by using the nanoprobe in the range of 4-220ng·mL-1, with the detection limits as low as 1.6 (colorimetry) and 3.4ng·mL-1 (fluorometry). The assay was applied to the detection of Hep in (spiked) human serum with satisfactory results. Graphical abstractSchematic illustration for colorimetric and fluorometric determination of heparin based on the use of a nanoprobe consisting of gold nanoclusters (AuNCs) and gold nanoparticles (AuNPs) with polyethyleneimine (PEI) as the mediator.