MnCO3 as New Electrochemiluminescence Emitter for Ultrasensitive Bioanalysis of β-Amyloid1-42 Oligomers Based on Site-directed Immobilization of Antibody.

In this work, an electrochemiluminescence (ECL) immunosensor was proposed utilizing MnCO3 nanospheres as a novel ECL luminophor and HWRGWVC (HC-7) heptapeptide as an efficient antibody capturer for site-directed immobilization with high affinity. MnCO3 nanospheres that prepared by homogeneous precipitation method exhibited high ECL efficiency, low toxicity, favorable biocompatibility and excellent stability. After the functionalization of poly dimethyl diallyl ammonium chloride (PDDA), the obtained MnCO3/PDDA could combine with gold nanoparticles (Au NPs) via electrostatic interaction (MnCO3/PDDA/Au). Besides, HC-7 as a small peptide ligand, has demonstrated to bind Fc portion of antibody with high affinity. Since the end of HC-7 is a cysteine, it can connect to MnCO3/PDDA/Au via Au-S bond. Then, the antibody could be effectively captured by HC-7 through specific interaction with a better maintained activity than traditional coupling reaction. For verifying the practicability of the constructed immunosensor, β-Amyloid1-42 oligomers (Aβ) was employed as an analyte. Based on the above points, the immunosensor performed favorable ECL property to Aβ concentrations in a wide linear range (0.1 pg/mL-10 ng/mL) with a low detection limit (19.95 fg/mL). With excellent repeatability, selectivity and stability, this method opened up a new avenue for realizing the ultrasensitive detection of Aβ and other biomarkers in real sample analysis.