Detection of human leptin in serum using chemiluminescence immunosensor: Signal amplification by hemin/G-quadruplex DNAzymes and protein carriers by Fe3O4/polydopamine/Au nanocomposites

• Published in: Sensors and actuators. B, Chemical Vol. 221; pp. 792 - 798
• Main Authors: He, Yuezhen, Sun, Jian, Wang, Xiaoxun, Wang, Lun
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.12.2015
• Subjects: Amplification; Antibodies; Biosensor; Catalysis; Chemiluminescence; DNAzymes; Fe3O4/polydopamine/Au; G-quadruplex; Gold; Human; Human leptin; Immunosensors; Magnetic nanocomposite; Nanocomposites; Fe3O4/polydopamine/Au; Human leptin; DNAzymes; Magnetic nanocomposite; Biosensor; G-quadruplex
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2015.07.022

In this work, we described a chemiluminescence immunosensor for ultrasensitive and selective detection of human leptin. Biocompatible three-layer superparamagnetic core–shell Fe3O4/PD/Au nanocomposites were proved to be an ideal protein carrier for analyte separation and enrichment. The hemin/G-quadruplex DNAzymes were employed to catalyze luminol–H2O2 chemiluminescent reaction for signal amplification. The DNAzymes, as a mimicking peroxidase, exhibited far higher catalytic activity than the natural enzyme HRP in strong alkaline medium. Therefore, the proposed immunosensor has a great potential for easy, highly sensitive and specific detection of a wide range of target molecules in disease diagnosis and clinical medicine. •The biosensor based on superparamagnetic Fe3O4@Au and hemin/G-quadruplex DNAzymes.•Fe3O4@Au were prepared by in situ method with polydopamine as a substrate adhesion.•DNAzymes were effective on catalyzing the chemiluminescence reaction of luminol–H2O2.•Sensitive detection of leptin was achieved by the purification/amplification protocol.•The sensing system held great potential for detecting other biomolecules of interest. A sandwich chemiluminescence (CL) immunosensor for sensitive detection of human leptin was developed with a multiple signal amplification strategy from catalytic hemin/G-quadruplex DNAzymes and functional superparamagnetic nanocomposites. To construct this sensing platform, core–shell structural Fe3O4/polydopamine (PD)/Au superparamagnetic nanocomposites were synthesized by an in situ method with PD as a substrate adhesive. These nanocomposites were further characterized by scanning electron microscopy, transmission electronic microscopy, energy-dispersive spectroscopy, Fourier transform infrared spectrum and a vibrating sample magnetometer at room temperature. In this immunosensor, the monoclonal anti-human leptin antibody (capture antibody) was bound to the Fe3O4/PD/Au nanocomposites. Human leptin, biotinylated detection antibodies and streptavidin-DNAzymes were successively combined the above-mentioned nanocomposites to form sandwich-type immunocomplex through specific interactions. The magnetic particles loaded with the immunocomplex were separated by an external magnet, and the DNAzymes in the immunocomplex greatly enhanced the CL emission of the luminol–H2O2 system. The immunosensor exhibited a high sensitivity, a good specificity, and a wide linear range for human leptin detection from 1.0pgmL−1 to 8.0×102pgmL−1 with a low detection limit of 0.3pgmL−1. This sensor is one of the most sensitive methods for leptin detection due to the highly efficient catalysis of the DNAzymes and analyte enrichment on magnetic capture.