Lixin Wang,Yuhong Liu,Jilin Yan,Huiling Li,Yifeng Tu
Coronary heart disease (CHD) poses an important threat to human health, and its pathogenesis is the formation of atheromatous plaques in coronary ventricles. Compared to other biomarkers, lipoprotein-associated phospholipase A2 (Lp-PLA2), which is involved in multiple processes of atherosclerosis, is a noticeable inflammatory biomarker related to CHD. Herein, using a multifunctional nanocomposite containing a CoFe Prussian blue analogue (PBA) and Au nanoparticles (AuNPs) (AuNPs@CoFe PBA) as a sensing substrate, an electrochemiluminescent (ECL) immunosensor was developed for the highly sensitive detection of Lp-PLA2. Benefiting from the synergistic effect of the PBA and AuNPs, the nanocomposite exhibits excellent peroxidase-like activity and can catalyze the luminol–ECL reaction, amplifying the ECL signal by ∼29-fold. Meanwhile, the enlarged specific surface area of the nanocomposite and the presence of abundant AuNPs allow the immobilization of more antibody proteins, thereby improving the sensing response of the immunosensor. When the target Lp-PLA2 is captured by the antibody on the sensor surface, the sensor emits a reduced ECL signal because of the increased mass and electron transfer resistance due to the formation of the immune complex. Under optimized conditions, the constructed ECL immunosensor exhibits a broad linear range from 1 to 2200 ng/mL and a low detection limit of 0.21 ng/mL. Additionally, the ECL immunosensor exhibits high specificity, stability, and reproducibility. This work provides a new approach to diagnose CHD and broadened the application of the PBA in the field of ECL sensors.
A portable photothermal immunoassay based on Au-coated magnetic Fe 3 O 4 core-shell nanohybrids (Au-Fe 3 O 4 ) was developed for point-of-care (POC) testing of lipoprotein-associated phospholipase A 2 (Lp-PLA 2 ) on a digital near-infrared (NIR) thermometer. Au-Fe 3 O 4 photothermal materials were first synthesized through reverse micelle method, and then functionalized with polyclonal rabbit anti-human Lp-PLA 2 antibody. A sandwiched immunoreaction was carried out in polyclonal mouse anti-human Lp-PLA 2 antibody-coated microplate using Au-Fe 3 O 4 -labeled antibody as the detection antibody. With formation of sandwich-type immunocomplex, the captured Au-Fe 3 O 4 on the plate converted the light into heat under an 808-nm laser irradiation (1.5 W cm −2 ), thereby resulting in the increasing temperature of the detection solution. The temperature variations relative to surrounding temperature was determined on a portable NIR thermometer. Several labeling protocols with gold nanoparticle, Fe 3 O 4 nanoparticle, or Au-Fe 3 O 4 nanohybrids were investigated for determination of Lp-PLA 2 and improved analytical features were achieved with the core-shell Au-Fe 3 O 4 nanohybrids. Under optimum conditions, Au-Fe 3 O 4 -based immunoassay exhibited good photothermal responses for the detection of Lp-PLA 2 with a dynamic linear range of 0.01–100 ng mL −1 at a low detection limit of 8.6 pg mL −1 . Good reproducibility and intermediate precision were less than 9.7%. Other biomarkers or proteins did not interfere with responses of this system. An acceptable accuracy was acquired for analysis of human serum sample between Au-Fe 3 O 4 -based photothermal immunoassay and commercialized human Lp-PLA 2 ELISA kit.
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