Detection of microbes in environmental sys using electrochemical biosensor

Abstract

The presence of sulfate-reducing bacteria (SRB) in environmental systems can be harmful to the environmental. For example, the hydrogen sulfide which is a product of SRB will react with metal ions in the water to produce metal sulfides. These metal sulfides are insoluble leading to the dark color of sludge. Additionally, H2S can be converted to sulfuric acid that jeopardize concrete and steel within wastewater environments which can be devastating. Moreover, SRB can provide a corrosion problem when metal structures are exposed to water which contains sulfate. An electrochemical biosensor that can detect the presence of bacteria even at a very low concentration is necessary in order to maintain the system free of microbial impacts. In this study, an electrochemical biosensor was investigated by immobilizing antibodies on a gold electrode. First the surface of gold electrode was modified with an alkane thiolate self-assembled monolayer (SAM). Then, the antibodies were attached to the SAM. SAMs with different alkyl chain lengths (3MPA, 6MHA, 8MOA, 11MUA) were studied in order to compare the effects of SAM’s height on sensing efficiency using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The longer alkyl chains showed more blocking behavior against the electron transfer than the short chains. The immobilization of antibodies and binding of bacteria to the gold electrode was observed to increase the electron transfer resistance. In addition, the resistance to the electron transfer increased as the bacteria concentration increased.