The Electrochemical Sensor For The Ultrasensitive Detection Of S-ovalbumin And Ovomucoid In Egg White

The S-ovalbumin and ovomucoid in egg white were taken as research objects,the electrochemical molecularly imprinted sensor and immunosensor were prepared using molecular imprinting technique and electrochemical methods based on new nanomaterials to selectively quantify S-ovalbumin and ovomucoid.The main findings are as follows:?1?Since the content of S-ovalbumin in egg white has significant correlation with the freshness and quality of chicken egg,using S-ovalbumin as an indicator to estimate egg freshness and quality is promising and meaningful.The scan cycles,scan rate,template extraction time and incubation time were optimized by cyclic voltammetry?CV?and differential pulse voltammetry?DPV?to prepare polypyrrole molecularly imprinted sensor?MIPs?that could selectively recognize S-ovalbumin.The optimal conditions were 18 cycles,100 mV/s,1.5 h and 40 min,respectively.The micro-structure of MIPs and nonMIPs were characterized by field emission scanning electron microscopy?FE-SEM?.The DPV was used to evaluate the relationship between different concentrations of S-ovalbumin and changes of peak current.The results showed that there is a significant dependency between S-ovalbumin concentration and peak current when the concentration changes from 10-6 mg/mL to 10-3 mg/mL.The MIPs exhibited a selective response to S-ovalbumin,and therefore,has the potential to be used for the detection of S-ovalbumin.?2?An electrochemical sensor for S-ovalbumin detection was fabricated based on molecularly imprinted polymer?MIP?on the glass carbon electrode modified with multiwalled carbon nanotubes?MWCNTs?and chitosan?CS?.The modified materials were characterized by infrared spectrometry and scanning electron microscopy.The performance of the modified electrodes,the relation between response current and analyte concentrations as well as the selectivity and practicability of MIP sensor were systematically evaluated by cyclic voltammetry,differential pulse voltammetry and electrochemical impedance spectroscopy.Under the optimum operating conditions,the fabricated electrochemical sensor showed a linear current response to the target concentration in the range from 10^-8 to 10^-4 mg/m L with a detection limit of 2.95×10-9 mg/mL in S-ovalbumin detection.Additionally,the proposed sensor exhibited good selectivity,high sensitivity and desirable stability.?3?The Fe₃O₄@Au NPs composites,synthesized by co-precipitation method and sodium citrate reduction,were characterized by means of UV-Vis spectroscopy,FT-IR spectroscopy,X-ray diffraction and scanning electron microscope.The results confirmed the magnetic core/gold shell structure of Fe₃O₄@Au NPs.An electrochemical immunosensor for the detection of S-ovalbumin was prepared by immobilizing the ovalbumin antibody on the surface of Fe₃O₄@Au NPs modified glass carbon electrode.The stepwise assembly process of the immunosensor was characterized by cyclic voltammetry?CV?and electrochemical impedance spectroscopy?EIS?.The differential pulse voltammetry?DPV?determined the optimizing antibody concentration,reaction temperature and pH,demonstrated that there is a significant concentration-dependent relation between peak current and S-ovalbumin with a detection range from 10-12 to 10-7 mg/m L and 10-6 to 10-2 mg/m L,a detection limit of 2.35×10^-13 mg/mL.The proposed immunosensor exhibited excellent selectivity and stability,therefore,has the potential for detecting real sample.?4?The GO-Au NPs composites,synthesized by sodium citrate reduction,were characterized by means of UV-Vis spectroscopy,FT-IR spectroscopy,X-ray diffraction and scanning electron microscope.The ovomucoid electrochemical immunosensor was established through immobilizing the ovomucoid antibody on the surface of modified electrode based on the Au-S bond and active groups of GO.The cyclic voltammetry?CV?,differential pulse voltammetry?DPV?and electrochemical impedance spectroscopy?EIS?were used to characterize the stepwise assembly process of the immunosensor,to investigate the relationship between peak current and concentration of ovomucoid,to determine the anti-interference of immunosensor.The results showed that there is a significant negative-relation between peak current and ovomucoid concentration with a detection range from 10^-8 to 10-1 mg/mL and a detection limit of 1.32×10-9 mg/mL.The proposed immunosensor exhibited excellent selectivity and stability to ovomucoid.