Study On The Development Of Electrochemical Immunoassays For Rapid Detection Of Tetrabromobisphenol A And Bisphenol A In The Environment

Emerging pollutants have persisted in the environment over the years due to anthropogenic activities that result in their distribution,which threatens human life and the planet.Tetrabromobisphenol A（TBBPA）and Bisphenol A（BPA）are typical pollutants worldwide due to their toxicity and accumulation,leading to detrimental effects on biodiversity and human health,despite being found at lower concentrations in the environment.Traditional analytical techniques have been applied to detect these pollutants in different environmental matrices;however,their drawbacks include complex sample pretreatment,expensive equipment,time consumption,and the need for skilled personnel,which prevents their wide range of application.As a result,researchers have focused on developing simple,cost-effective,sensitive,accurate,and reliable techniques to detect trace pollutants in environmental and food samples.Electrochemical immunoassay was selected as an ideal methodology due to its simple pretreatment,cost effectiveness,fast analysis process and simple operation.The detection is rapid,and a small sample volume is required to detect the TBBPA and BPA in water and food samples.Based on antigen-antibody immunoreaction,magnesium oxide,ceria oxide,gold-palladium nanoparticle,gold nanoparticle combined with other nanomaterials were synthesized to establish four immunoassay methods to overcome the challenges of the traditional instrumental analysis techniques.The details of the study are outlined below1.In this work,a novel competitive electrochemical immunosensor was developed.Gold palladium bimetallic nanoparticles were successfully synthesized and modified by amine（-NH₂）functionalized-nanoflower-like manganese oxide（NH₂-f Mn O₂）for the rapid and sensitive detection of TBBPA in environmental waters.The MWCNTs modified GCE was employed to load TBBPA-antigens（Ag）through the effects of adsorption for the design of a highly sensitive immunosensor,which provided a large surface area for the specific recognition between antigen-antibody reactions.Meanwhile,Au Pd-NH₂-f Mn O_2,the signal amplifier,was employed as a carrier tag to label secondary antibody（Ab₂）,which showed excellent catalytic ability toward H₂O₂.The Au Pd NPs boosted TBBPA oxidation,thereby generating improved signals.Hence,the competitive biosensor presented superior performances under optimal conditions,such as good sensitivity（LOD,0.10 ng/m L;based on S/N=3）and satisfactory accuracy（recoveries,84-120%;CV,2.35-6.24%）.The proposed method was employed to analyze TBBPA in waters from various sources,indicating a great potential for the sensitive determination of trace TBBPA in aquatic environments.2.In the previous work,although the immunosensor had good sensitivity,it could be compromised by the inability of the multi-walled carbon nanotubes to immobilize antigens because they easily aggregate and cause the output signal to be unstable.As a result,a more robust and highly stable platform is required.This chapter reports an indirect competitive immunosensor for TBBPA detection based on the signal amplification system.Palladium nanospheres in-situ reduced on the surface of Mn O₂ nanosheets hybrid（Mn O₂/Pd）were used as the label for the secondary antibody through the Pd-N bond,and gold-toluidine blue composite was loaded onto MWCNTs（MWCNTs/Au-TB）,which functioned as the platform for the immunosensor.The spherical structure of Pd had abundant catalytic active sites,which enhanced the catalytic activity of Mn O₂/Pd as the label,hence amplifying the signal response.Besides,MWCNTs/Au-TB improved electron transfer and produced a strong signaling pathway for immobilizing antigens through the Au-NH₂ bond,specifically recognizing primary antibodies to improve sensitivity.The immunosensor had a linear concentration range of 0-81 ng/m L,a low detection limit of 0.17 ng/m L（S/N=3）,with good stability,selectivity,and reproducibility.Additionally,the acceptable accuracy and recoveries（recoveries,92-124%;CV,3.3-8.8%）in the real water sample analysis indicated that this strategy is promising for emerging pollutant analysis.3.Insights obtained from the single response systems in the above studies,inspired the design of a novel electrochemical（EC）sensing matrix for a sensitive immunoassay of tetrabromobisphenol A（TBBPA）by combining a competitive immunoreaction and dual signal output.In this study,a rod-like Mn O₂ reduced graphene-Au（Mn O₂-r GO-Au）was utilized as a sensing platform to immobilize TBBPA antigens to label TBBPA antibodies and Co Cu-embedded mesoporous Ce O₂（Co Cu-m Ce O₂）with abundant oxygen vacancies as a catalytic probe.Remarkably,Co and Cu on the mesoporous Ce O₂（m Ce O₂）exposed massive active sites that produced additional oxygen vacancies to ameliorate the electrocatalytic activity and redox performance of the m Ce O₂ nanoparticle.Besides,Co Cu-m Ce O₂ acted as the secondary antibody conjugation label based on an amine functionalized bridge between m Ce O₂ and the antibody and also improved the electrochemical performance.Under the optimized conditions,the fabricated immunosensor displayed;（i）a wide linear range for TBBPA detection,ranging from 0-243 ng/m L;（ii）lower detection limits of 0.034 ng/m L（according to the amperometric i-t method）and 0.076ng/m L（calculated by DPV method）,respectively,which was lower than the enzyme-linked immunosorbent assay（ELISA）with LOD 0.59 ng/m L;（iii）satisfactory accuracy and reliability（recoveries,95-126.2%;CV,3.36-8.9%measured by amperometric i-t method and recoveries,95.4-126%;CV,3.49-9.62%using DPV method）.The designed immunosensor exhibited good sensitivity,accuracy,and an excellent potential for trace TBBPA determination from various samples.4.In this chapter,a novel,sensitive,and competitive amperometric immunosensor was designed to detect trace bisphenol A（BPA）based on gold nanoparticles（GNP）as bio-conjugate.The bioconjugate was decorated with a copper-capped structure（Cu SO₄,AA）to generate Cu particles via HNO₃ reaction,which caused a decline in the signal response.Besides,after the introduction of H₂O₂to react with Cu²⁺a Fenton reaction occurred and·OH was produced,which increased the signal response.The·OH generated stimulated the degradation of methylene blue（MB）coated under Au on the electrode surface,resulting in a further decline of the current response,which correlated with the target analyte concentration.The outcome led to a remarkable enhancement of the analytical performance.Under optimum detection parameters,this novel immunosensor could sensitively detect BPA.A linear range of 1×10^-4-1×10~2 ng/m L was derived along with a low detection limit of 1.59×10^-4 ng/m L.Furthermore,our method displayed good accuracy（recoveries,96-104.7%;CV,2.4-8.5%）.This study will contribute to developing novel Fenton reactions for electrochemical immunosensors.