Novel Conducting Polymer Sensor for the Detection and Analysis of Biothiols

Abstract

Biothiols (biological thiols) are sulfur-containing compounds, that are extremely important molecules with a large range of diversity in their functions. These molecules are found in all parts of the body and are vital for processes such as cell-signaling molecules and (anti)oxidation in the body. Abnormal levels of biothios can lead to, or be indictive of, a range of diseases and conditions. These molecules can be highly reactive and unstable, as such detection of these molecules has proven to be extremely difficult. and there is currently limited methods for their detection and analysis, all of which lack in accuracy, selectivity and/or efficiency. The development of a new method for the detection of thiols could prove to be a breakthrough in the research and understanding of these critical molecules. The synthesis, development and use of an innovative sulfide chemical sensor, that allows for fast, accurate and selective detection of biothiols would be a way to address this need. The sensor developed and investigated in this work is based on a novel, conducting polymer with the detection method relying on the thiol’s formation of a strong disulfide bond between the analyte and the conducting polymer sensor which would induce changes in the properties of the conducting polymer. In this project, a new novel methoxycarbonylsulfenyl-functionalised EDOT monomer, 1, was made through a five-step synthesis, and in the process also led to the synthesis of a range of other functionalised EDOT monomers. Polymerisation of the functional monomer resulted in poor polymerisation, along with poor detection of thiols, through low electrical activity of the polymer. Fortunately, co-polymerisation of EDOT-thioacetate 6 and EDOT to form poly(EDOT-thioacetate-co-EDOT), followed by deacetylation of the polymer on the electrode was used to successfully form a co-polymer of PEDOT and PEDOT-thiol, poly(EDOT-thiol-co-EDOT). This co-polymer showed excellent electrical activity and when exposed to glutathione, was able to detect it in solution. Various parameters of forming the co-polymer were optimised for sensing performance and the optimised co-polymer was used to form a calibration curve, with a linear relationship between sensing signal and concentration of glutathione for the range of 1 μM and 600 μM, and giving an LOD of 0.32 μM. The sensor and its function were explored using a range of characterisation techniques and a series of additional experiments showed that the developed sensor was highly recyclable and selective, with regard to interfering agents. This was an excellent result and meant that all the aims of this project were achieved, in the successful development of a conducting-polymer-based sensitive, selective, efficient and recyclable sensor to detect biothiols. Future work will be based on the testing of this developed technology for detection of other (bio)thiols and the development of this novel technology to become a sensing device for monitoring of human health.