Quorum-Signaling Molecule Detection Based on Composite Sensors: Metal Oxides/Conducting Polymer

Abstract

Abstract N-hexanoyl-l-homoserine lactone (C6-HSL) is a distinctive signal produced by Gram-negative bacterial strains. The signal is used to cell-to-cell communication. Oil and gas companies are suffering from Microbiologically-influenced corrosion (MIC) induced Sulfate-reducing bacteria (SRB. SRB induce severe pitting corrosion on the metal surface especially when attached and form biofilms. Nowadays, scientists are looking for an applicable method to detect SRB-biofilms. Metal oxides (MOx) intercalated into a polymers matrix, specifically conducting polymers (CPs), to sense different biological molecules effectively such as C6-HSL due to its ability to form a coordination bond and its high selectivity. Therefore, this work was directed to provide a novel quorum-signaling molecule, C6-HSL, sensing technique to distinguish invisible SRB-biofilms attached to a metal surface. Hence, two different MOx/Polyaniline-Dodecyl benzene sulfonic acid (PANI-DBSA) composites (ZnO/PANI-DBSA and Fe2O3/PANI-DBSA) were synthesized and structurally characterized. Afterwards, the composites were applied with carbon paste 1% by weight over a carbon working electrode (WE) to detect the C6-HSL qualitatively and quantitatively via an electrochemical analysis. The electrochemical impedance spectroscopy (EIS) verified the ability of the obtained composites to monitor the C6-HSL produced by SRB-biofilm compared to the standard material. The monitoring composites achieved the intended results where the observation swapped from 50 to 1000 ppm of the C6-HSL concentrations. The limit of detection (LOD) of the ZnO/PANI-DBSA and Fe2O3/PANI-DBSA was 624 and 441 ppm, respectively. Furthermore, the SRB-biofilm was confirmed by a calorimetric measurement in addition to EIS, where the outcomes were compatible.