Colorimetric detection of proteins based on target-induced activation of aptazyme.

The detection of protein is vital to fundamental research as well as practical applications. However, most detection methods depend on antibody-based assays which are faced with many shortcomings. Herein, we propose a colorimetric method for protein assays based on target-triggered activation of aptazyme, which may offer simple, rapid and cost-effective detection of the target protein. In this method, the conformation change of aptazyme induced by target protein is designed to be associated with aptazyme activation. Consequently, in the presence of the target protein, the designed DNA linkers will be cleaved into two fragments that fail to cross-link gold nanoparticles (GNPs), thus the color of GNP solution remains red, while the color will be changed in the absence of the target. Because of the advantages of aptazyme such as economic synthesis, stable, easy modification and its ability to accomplish signal recognition and signal amplification simultaneously, the method is thermostable, simple and cost-efficient. In this work, we have taken the detection of vascular endothelial growth factor (VEGF) as an example, which can present an analytical performance with as low as 0.1 nM detection limit, spanning a detection range of 3 orders of magnitude. What is more, the principle of this proposed new method can be extended as a universal assay method not only for the detection of analytes which have an aptamer but also for those analytes that have ligands.