Electrochemical detection of foodborne pathogen Aeromonas hydrophila by DNA hybridization biosensor

The paper describes an electrochemical DNA biosensor used for the detection of Aeromonas hydrophila. This opportunistic pathogen is recognized as an emerging foodborne hazard and is associated with a variety of virulence factors including production of cytotoxic enterotoxin aerolysin. The genosensor recognition layer was prepared using mixed self-assembled monolayer (SAM) consisting of thiolated single-stranded DNA probe (ssDNA) and diluent molecules – mercaptoalcohol: mercaptoethanol (MCE) or mercaptohexanol (MCH) or mercaptononanol (MCN). The voltammetric examination of double-layer capacitance of biosensor recognition interface supported by chronocoulometric quantitation of DNA present on the electrode surface showed that mixed ssDNA and MCH monolayer revealed the lowest defectiveness. Its double-layer capacitance equaled 4.0 μF cm−2 and ssDNA probe surface coverage reached 8.5 × 1011 molecules cm−2 of gold electrode surface. Chronocoulometric quantitation of DNA and square wave voltammetry (SWV) measurements of electroactive indicator, methylene blue (MB) were performed to investigate the influence of hybridization reaction time, concentration of target DNA fragments, and presence of non-complementary DNA on the electrochemical response of genosensor recognition interface. The biosensor enabled distinction between the DNA samples isolated from A. hydrophila (present at the concentration of 2.5 μg cm−3) and other microbial DNA.