| Vibrio are widely distributed in coastal and estuarine environments where they are closely associated with marine animals,plankton,algae or abiotic surfaces.Vibrio,especially Vibrio parahaemolyticus,is one of the most important threats to public health.Furthermore,in the last decades,an increase in Vibrio parahaemolyticus infections of worldwide has caused mass mortalities of marine animals,leading to important economic losses.Thus,a simple,fast,inexpensive and reliable method for efficient detection and identification of Vibrio parahaemolyticus is urgently needed.Compared to current detection methods,electrochemical sensors offer several advantages including high sensitivity,low-cost,easy-to-use and allowing real-time analysis.Electrochemical sensors have been prominently applied for Vibrio parahaemolyticus detection.To improve the sensitivity,selectivity and stability of sensors,an effective way is the preparation of modified electrodes by design and optimization of nanocomposites.In this paper,three Vibrio parahaemolyticus DNA electrochemical sensors based on functionalized nanosheet composites were constructed and corresponding detection methods were established.The main research contents are as follows:?1?The electrode was modified by IL-GO-ELDH nanocomposites which were prepared by ionic liquid?IL?covalently functionalized graphene oxide?GO?and exfoliated hydrotalcite-like nanosheet?ELDH?assemblies.What's more,the Vibrio parahaemolyticus DNA electrochemical sensor was constructed based on the principle of specific hybridization of the probe single-stranded DNA with the complementary single-stranded DNA.IL-GO-ELDH provided unique film-forming property,large surface area,high conductivity and good dispersibility of each component,facilitating electron transfer for sensitive and selective detection of Vibrio parahaemolyticus DNA with excellent selectivity,fast responses,and a low detection limit.The probe DNA was immobilized on the surface of the modified electrode by covalent bonding.Differential pulse voltammetry was applied to monitor the target DNA hybridization event using[Fe?CN?6]3-/4-as an electrochemical indicator.Under the optimal experimental conditions,the electrochemical DNA sensor could detect target DNA concentrations in the range of1.0×10-15-1.0×10-77 M with a detection limit of 2.63×10-16 M?S/N=3?.?2?ZIF-8 was grown in situ on GO nanosheet substrate.IL-ZIF-8@GO nanocomposites were synthesized via IL covalent functionalization of ZIF-8@GO.IL-ZIF-8@GO nanocomposite assembled electrode was obtained as an electrochemical sensor of Vibrio parahaemolyticus DNA after being immobilized a single-stranded probe DNA by covalent bond method.The probe DNA was bound with the addition of target DNA to form the double-stranded structure on the electrode surface,which led to a significantly decrease of peak current of electrochemical indicator[Fe?CN?6]3-/4-.Under optimal conditions,the peak current value of DPV decreased linearly with the target DNA concentrations in the range of 1.0×10-16-1.0×10-7 M.The detection limit was estimated to be 3.62×10-1717 M?S/N=3?.The experimental results show that the electrochemical DNA sensor based on IL-ZIF-8@GO has good selectivity and high sensitivity,which can be attributed to the high porosity,large specific surface area and excellent conductivity of IL-ZIF-8@GO complex.?3?CoAl-LDH derived from ZIF-67 was combined with GO by ion exchange reaction and electrostatic assembly method.Thi-rGO-LDH nanocomposite was prepared by thionine?Thi?functionalization and hydrazine hydrate reduction of LDH-GO.A label-free electrochemical sensor was fabricated for Vibrio parahaemolyticus DNA detection based on Thi-rGO-LDH nanomaterials.Thi in the Thi-rGO-LDH nanocomposite retained its excellent redox activity and could be directly used as an indicator signal by the electrochemical signal of thionine.The probe DNA was bound with the addition of target DNA to form the double-stranded structure on the electrode surface,which hindered the transfer of electrons and led to a significantly decrease of the electrochemical signal of Thi.Therefore,the target DNA sequence could be detected by monitoring the electrochemical signal changes of Thi after probe DNA immobilization and target DNA hybridization.And the immobilization and hybridization behaviors were assessed using differential pulse voltammetry.Under the optimal experimental conditions,the peak current value of DPV decreased linearly with the logarithm of the target DNA concentration in the range of 1.0×10-17-1.0×10-7 M.The detection limit was estimated to be 6.83×10-18 M?S/N=3?.The experimental results show that the electrochemical DNA sensor based on Thi-rGO-LDH nanocomposites exhibit good reproducibility,stability and selectivity. |
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