期刊
ANALYTICAL CHEMISTRY
卷 92, 期 13, 页码 9370-9378出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.analchem.0c01773
关键词
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资金
- Natural Sciences and Engineering Research Council of Canada (NSERC)
- National Natural Science Foundation of China [31601548]
- China Scholarship Council (CSC) Scholarship
- Hubei Youth Science and Technology Morning-light Program [2019]
Target directed aptamer adsorption by gold nanoparticles (AuNPs) has been widely used to develop label-free colorimetric biosensors. However, the potential interactions between target molecules and AuNPs have not been considered, which may lead to misinterpretation of analytical results. In this work, the detection of dopamine, melamine, and k(+) was studied as model systems to address this problem. First, dopamine and two control molecules all induced the aggregation of citrate-capped AuNPs with apparent K-d's of 5.8 mu M dopamine, 51.6 mu M norepinephrine, and 142 mu M tyramine. Isothermal titration calorimetry measured the aptamer K-d to be 1.9 mu M dopamine and 16.8 mu M norepinephrine, whereas tyramine cannot bind. Surface enhanced Raman spectroscopy confirmed direct adsorption of dopamine, and the adsorbed dopamine inhibited the adsorption of DNA. Using a typical salt-induced colorimetric detection protocol, a similar color response was observed regardless of the sequence of DNA, indicating the observed color change reflected the adsorption of dopamine by the AuNPs instead of the binding of dopamine by the aptamer. For this label-free sensor to work, the interaction between the target molecule and AuNPs should be very weak, while dopamine represents an example of strong interactions. For the other two systems, the melamine detection did not reflect aptamer binding either but the K+ detection did, suggesting melamine also strongly interacted with AuNPs, whereas K+ had very weak interactions with AuNPs. Since each target molecule is different, such target/AuNP interactions need to be studied case-by-case to ensure the sensing mechanism.
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