Development of An Electrochemical Immunosensor for Environmental Monitoring of Polychlorinated Biphenyls (PCBs) in Soil Environment

Abstract

Polychlorinated biphenyls, PCBs are a type of chemical contaminant known as persistent organic pollutants (POPs). They consist of biphenyl molecules covalently bonded with one to ten chlorine atoms. PCBs pose a threat to ecosystems and food safety due to their high toxicity, long-term stability, poor degradation, and bioaccumulation. The current methods, although sensitive, have their limitations, for example, time-consuming, laborious, and costly. Further, the instrumentation cannot be used for on-site analysis. The aim of this research is to develop a novel electrochemical method that will be capable of providing a direct, portable, cost-effective, and easy method for analysing and monitoring PCBs in the environment. For the first time, a self-assembled monolayer was used to modify an electrode as a method for fabricating a transducer for detection of PCBs by using a gold electrode, it was modified with 11- mercaptoundecanoic acid (11-MUA), and the activation of the carboxylic acid terminal was performed by cross-linking 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hyrodsuccinmide (NHS). The electrochemical behaviour of the electrode was investigated by CV (Cyclic Voltammetry), LSV (Linear Sweep Voltammetry) and EIS (Electrochemical Impedance Spectroscopy) using a ferrocyanide/ferricyanide redox pair. It was found that the indirect competitive assay showed the best performance for Aroclor1254 detection, with a commercial Polyclonal chicken antibody (IgY) specific to PCB was used as primary antibody. The limit of detection was found at 0.20 ng/ml using bare gold electrode. However, the sensitivity of the sensor was increased after the electrode surface modification was found at 0.09 ng/ml. A novel electrochemical immunosensor method showed a good performance with a 3-fold decrease in sensitivity achieved after the surface modification. The electrode coated with coating conjugate was found stable for more than 25 days at 4 ˚C. In conclusion, this Ph.D. thesis demonstrates that the integration of electrochemical techniques with immunoassay methods can achieve detection limits as low as required for in-situ and real-time analysis of soil samples. It was found that the electrochemical immunosensor method showed better results compared to ELISA and that was verified with GC-MS. The usage of this a novel electrochemical immunosensor as a complement to the electrochemical studies not only enhanced the quality of the research but also contributed to the construction and improvement of immunosensors. As a result, they represent an accurate and a new robust method that can be applied to microsensors and microfluidic systems for the effective control and prevention of PCBs in the environment.