Detection of Ostreopsis cf. ovata in environmental samples using an electrochemical DNA-based biosensor.

Ostreopsis cf. ovata is a benthic microalga distributed in tropical and temperate regions worldwide which produces palytoxins (PlTXs). Herein, an electrochemical biosensor for the detection of this toxic microalga is described. The detection strategy involves isothermal recombinase polymerase amplification (RPA) of the target using tailed primers and a sandwich hybridisation assay on maleimide-coated magnetic beads immobilised on electrode arrays. The biosensor attained a limit of detection of 9 pg/μL of O. cf. ovata DNA (which corresponds to ~640 cells/L), with no interferences from two non-target Ostreopsis species (O. cf. siamensis and O. fattorussoi). The biosensor was applied to the analysis of planktonic and benthic environmental samples. Electrochemical O. cf. ovata DNA quantifications demonstrated an excellent correlation with other molecular methods (qPCR and colorimetric assays) and allowed the construction of a predictive regression model to estimate O. cf. ovata cell abundances. This new technology offer great potential to improve research, monitoring and management of O. cf. ovata and harmful algal blooms.