A highly sensitive colorimetric aptasensor for the detection of the vascular endothelial growth factor in human serum

Early detection of cancer is of great significance for disease prevention and diagnosis. However, the levels of most cancer markers are quite low in the early stages of disease, so it is urgent to develop a highly sensitive detection method. In this study, a label-free and highly sensitive colorimetric strategy was developed for the detection of the vascular endothelial growth factor₁₆₅ (VEGF₁₆₅) in human serum. First, a convenient biosensor was constructed by immobilizing VEGF₁₆₅ on a microplate, where aptamers bound with VEGF₁₆₅ to form a complex. Then, streptavidin labeled-horseradish peroxidase (HRP-SA) combined with the complex via the interaction between streptavidin and biotin, thus catalyzing the 3,3',5,5'-tetramethylbenzidine (TMB) and H₂O₂ system to produce colored products. In the presence of target, immobilized VEGF₁₆₅ and target competitively bound with the aptamers, resulting in a reduction of the colorimetric signal. Moreover, the optical density (OD) signal decreased with the increase of target concentration. The strategy showed a broad linear range (0.1-100 ng/mL) and a rather low detection limit of 10 pg/mL with good precision and selectivity. Further, the proposed method was successfully applied in detecting VEGF₁₆₅ in human serum. The detection results of serum samples showed that the proposed assay had a high correlation with CLEIA kits (r = 0.971, P = 0.001). It has potential for application in clinical research and diagnosis.