Sodium Dodecyl Sulfate Decorated Legionella pneumophila for Enhanced Detection with a GaAs/AlGaAs Nanoheterostructure Biosensor

Abstract The net electric charge associated with a bacterial strain is primarily defined by the number of available functional groups at its surface and we observed that it can determine the limit of detection of a charge-sensing biosensor. We have investigated the dynamic range of bacterial electric charge variations through binding negatively charged sodium dodecyl sulphate (SDS) molecules, with the objective of improving the detection limit of a charge-sensing GaAs/AlGaAs nanoheterostructure biosensor designed for detection of Legionella pneumophila. A two-fold increased zeta potential of L. pneumophila was measured at pH 7.4 following the exposure of these bacteria to an SDS solution at 0.02 mg/mL. Subsequently, it was possible to detect SDS decorated and heat-inactivated L. pneumophila at 103 CFU/mL. This illustrates the fundamental role of the bacterial electric charge in the operation of photocorrosion-based III-V semiconductor biochips. We discuss the mechanisms of bacterial interaction with SDS, critical aspects of decorating bacteria with this anionic surfactant and the channels responsible for charge transfer.