Ultrasensitive colorimetric immunoassay for hCG detection based on dual catalysis of Au@Pt core–shell nanoparticle functionalized by horseradish peroxidase

In this paper, an ultrasensitive colorimetric biosensor for human chorionic gonadotrophin (hCG) detection was designed from bottom-up method based on the dual catalysis of the horseradish peroxidase (HRP) and Au@Pt nanoparticles (NPs) relative to H 2 O 2 -TEM system. HRP and monoclonal mouse anti-hCG antibody (β-submit, mAb 1 ) were co-immobilized onto the Au@Pt NP surface to improve catalytic efficiency and specificity, which formed a dual functionalized Au@Pt-HRP probe with the mean size of 42.8   nm (D 50 ). The colorimetric immunoassay was developed for the hCG detection, and the Au@Pt-HRP probe featured a higher sensitivity in the concentration range of 0.4–12.8   IU   L −   1 with a low limit of detection (LOD) of 0.1   IU   L −   1 compared with the LODs of 0.8   IU   L −   1 for BA-ELISA and of 2.0   IU   L −   1 for Au@Pt, which indicated that the Au@Pt-HRP probe possessed higher catalytic efficiency with 2.8-fold increase over Au@Pt and 33.8-fold increase over HRP. Also, the Au@Pt-HRP probe exhibited good precision and reproducibility, high specificity and acceptable accuracy with CV being less than 15%. The dual functionalized Au@Pt-HRP probe as a type of signal amplified method was firstly applied in the colorimetric immunoassay for the hCG detection.