Highly sensitive antibody-aptamer sensor for vascular endothelial growth factor based on hybridization chain reaction and pH meter/indicator

Vascular endothelial growth factor (VEGF) is a crucial signaling protein for the tumor growth and metastasis, which is also acted as the biomarkers for various diseases. In this research, we fabricate an aptamer-antibody sensor for point-of-care test of VEGF. Firstly, target VEGF is captured by antibody immobilized on the microplate, and then binds with aptamer to form the sandwich structure. Next, with the assist of glucose oxidase (GOx)-functionalized ssDNAs, hybridization chain reaction occurs using the aptamer as the primer. Thus, GOx are greatly gathered on the microplate, which catalyzes the oxidization of glucose, leading to the pH change. As a result, the detect limit at a signal-to-noise was estimated to be 0.5pg/mL of target by pH meter, and 1.6pg/mL of VEGF was able to be distinguished by naked eyes. Meanwhile, this method has been used assay VEGF in the serum with the satisfactory results. The sensing principle of this sensor [Display omitted] •We fabricate an aptamer-antibody immunosensor for point-of-care test of VEGF.•Small size aptamer is applied instead of secondary antibody, which improves the bind kinetics.•Enzyme-free and isothermal HCR is introduced into the detection, which simplifies the experimental steps and times.•Low-cost pH meter and pH indicator have been used as the transducers instead of common large instruments.•0.5pg/mL of target could be detected by pH meter, and 1.6pg/mL of that is able to be distinguished by pH indicator.