Journal
BIOSENSORS & BIOELECTRONICS
Volume 98, Issue -, Pages 126-133Publisher
ELSEVIER ADVANCED TECHNOLOGY
DOI: 10.1016/j.bios.2017.06.038
Keywords
Enzyme-free immunosensor; Microcystin-LR; Hybridization chain reaction; G-quadruplex
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Funding
- National Scientific Foundation of China [21475047, U130214]
- Special Funds for Public Welfare Research and Capacity Building in Guangdong Province [2016B030303010]
- Program for the Top Young Innovative Talents of Guangdong Province [2016TQ03N305]
- National Undergraduate Scientific and Technological Innovation Project [201610564224]
- Foundation for High-level Talents in South China Agricultural University
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A novel multiple amplified enzyme-free immunosensor was developed for competitive immunoassay of microcystin-LR (MC-LR). Classical electrochemical immunosensors usually employ enzymes as biocatalysts to afford amplified signals, but the Proteolytic degradation and poor stability are still crucial problem. Herein, monodisperse core-shell mesoporous silica (SiO2@MSN)-functionalized DNAzyme concatamers were synthesized to load hemin and methylene blue (MB) as the mimic enzyme. Firstly, the surface of SiO2@MSN was conjugated with secondary antibody as the recognition of MC-LR antibody and with a DNA strand as the initiator. Two auxiliary DNA strands were then selected for the in-situ propagation to form a double-helix DNA through hybridization chain reaction (HCR), forming numerous DNAzymes (G-quadruplex/hemin) after the addition of hemin. Secondly, MB was inserted into the formed double-helix DNA, and also loaded in the brush-like structure of mesoporous SiO2@MSN. The molecular docking study showed that electrons can transfer more effectively with pi-pi stack of hemin/G-quadruplex and intercalation of MB/DNA, thus the catalytic ability of DNAzymes can be greatly improved. With the aid of MB, DNAzymes can catalyze the reduction of H2O2 to produce the electrochemical signal. This enzyme-free electrochemical immunosensor can successfully detect MC-LR in a range of 0.5 ng/L and 25 mu g/L with a detection limit of 0.3 ng/L. This stable, sensitive and selective nonenzymatic electrochemical immunoassay shows promise for applications in food and environmental monitoring.
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