Colorimetric determination of the early biomarker hypoxia-inducible factor-1 alpha (HIF-1α) in circulating exosomes by using a gold seed-coated with aptamer-functionalized Au@Au core-shell peroxidase mimic

An ultra-sensitive method is described here for the determination of HIF-1α (an early biomarker for myocardial infarction) in circulating exosomes in serum. Gold nanospheres were functionalized with a HIF-1α-binding aptamer via sulfydryl chemistry. The apt-AuNP-coated gold seeds were grown by seed-mediated growth, and this significantly increased the peroxidase-mimicking property the nanoparticles. A chromogenic system composed of 3,3′5,5′-tetramethylbenzidine and hydrogen peroxide was used. Absorbance at 652 nm increases linearly in the 0.3 to 200 ng L−1 HIF-1α concentration range, and the limit of detection is 0.2 ng L−1. The method was tested by analyzing rat serum from isoproterenol (ISO)-induced myocardial infarction. It allows HIF-1α to be directly determined in a 25 μL sample without preconcentration. The assay is not interfered by the polydispersity of exosomes released under either health and disease conditions.