Novel Electrochemical Aptamer Sensors For Highly Sensitive Detection Of Bisphenol A And ?-estradiol

Pollution problems caused by environmental hormones seriously grave threat to the environmental safety and human health.In recent years,excessive use of environmental hormones,including plastic products additives,hormones,pesticides and herbicides caused the pollution.Food,air and water are the main victims of the contaminants that may have impact on human and animal life.Therefore,it is particularly important to establish a simple,accurate,sensitive,rapid and on-line method for the determination of environmental hormone residues.Chromatographic methods,immunoassay,optical and electrochemical methods are the traditionally used assays for quantitative and qualitative measurement of environmental pollutants.Electrochemical analysis has the characteristics of simple equipment,easy miniaturization,on-line detection and no influence on the turbidity of samples,thus,combining the highly specificity molecular recognition ligand of aptamer with highly sensitive electrochemical technology has important research significance.The aim of this research is to develop novel electrochemical aptamer sensors for highly sensitivity and selectivity detection of bisphenol A and 17?-estradiol.The research contents of this paper mainly include the following three parts:1.Bisphenol A(BPA),an important compound that is classified as an environmental hormone.A novel electrochemical aptamer sensor for the determination of BPA was developed based on graphene modified glassy carbon electrode.Graphene oxide was reduced to graphene on line by electrochemical method,which overcame the disadvantages that drop coating prepared method was easy to fall off and unstable.The BPA aptamer DNA was immobilized on the graphene modified electrode through the interaction with graphene to prepare the BPA electrochemical aptamer sensor.Withferricyanide-ferrocyanide(1:1)as the electrochemical probe,quantitative determination of different concentration of BPA was used by differential pulse voltammetry through the bonding of aptamer with BPA induced the different blocking of the electron transfer of[Fe(CN)6]3-/4-.The results showed that the peak currents linearly correlated with the BPA concentration over a linear range of 1.0×10-15~ 1.0×10-11mol/L,with the detection limit of 3.3×10-16mol/L(S/N=3).The spike recovery of BPA in tap water was carried out,and the developed aptamer sensor could be used for the detection of BPA in tap water.2.An ultrasensitive electrochemical aptamer sensor for determination of BPA was successfully constructed based on gold nanoparticles(GNPs)coated molybdenum disulfide(Mo S2).GNPs and Mo S2 were stepwise modified on glassy carbon electrode(GCE).And these two nano-materials were used to increase the surface area of electrode to enhance the electron transfer rate,and finally amplify the sensor signal.The aptamer sensor was fabricated in sequence by self-assembling of thiolated hairpin-DNA probes onto the surfaces of the modified electrodes,and then hybridized with anti–BPA aptamer to form double-stranded DNA.Upon BPA target binding,the aptamer dissociated from their respective hairpin DNA into the solution and the single-stranded DNA could then tend to form a hairpin structure.Electrochemical measurements were performed using methylene blue as a redox indicator.The oxidation peak current of methylene blue accumulated on the electrode increased with increasing the concentration of BPA due to higher affinity for single strand DNA rather than double strand DNA.BPA can be detected in the concentration range from 10×10-16 to 1×10-11mol/L,the linear equation is(35)Ipa(?A)= 1.96 lg C(mol/L)+ 34.42(R=0.9990),and down to levels as low as 0.06 fmol/L.This study may offer a new approach with good analytical properties and potential applications to other environmental hormone.3.One of the most important endogenous estrogens is 17?-estradiol,which disturbed the endocrine system,and causing adverse effects on the growth,reproduction and development of human and animal.A new method based on gold nanoparticles(GNPs)double signal amplification electrochemical aptamer sensor for the detection of17?-estradiol was constructed.GNPs and Mo S2 nanocomposite modified glassy carbonelectrode was first prepared in the experiment.Then the 17?-estradiol aptamer DNA probe was fixed on the surface of the modified electrode by the self-assembly technique,using BSA instead of MCH to occupy the remaining free sites on the electrode surface,the partial complementary DNA of the thiolated end was hybridized with 17?-estradiol aptamer DNA,and the GNPs was assembled at the end of thiolated the partial complementary DNA.Finally,the electrochemical sensor was prepared by electrostatic action to absorb the electrochemical probe thionine to the GNPs surface.The use of GNPs and Mo S2 nanocomposite not only increases the load of the DNA probe,and also expands the number of the electrochemical probe thionine,and further improves the sensitivity of the method detection.A concentration and peak current within the range of1.0×10-14 to 5.0×10-12 mol/L,and the detection limit of(S/N=3)of 17?-estradiol was4.2×10-15 mol/L,the linear equation is ?I(?A)=0.83 lg C(mol/L)+12.21(R=0.9925).