Digital camera-based lipase biosensor for the determination of paraoxon

This work is focused on construction of a biosensor containing unique bacterial homogenate with high lipase activity and colorimetric type of assay where camera of a smartphone was chosen as a detector. The biosensor was constructed as a tool of lipase inhibitors and paraoxon served as a representative analyte inhibiting the lipase. Psychrophilic strains of bacteria isolated from in Antarctica were tested and the best isolate P4368 having huge lipase activity was chosen. Tween assay was performed as a standard method for lipase activity determination and indoxylacetate served as a substrate of lipase measurable by smartphone camera and R, G and B color channels digital analysis. Bacteria were homogenized and immobilized on polyvinylidene difluoride membrane and indoxylacetate was immobilized in the proximity of the homogenate. Paraoxon ethyl was analyzed by the standard method and by the camera-based biosensor. The biosensor-based assay was found to determine paraoxon with limit of detection 3.72 x 10(-8) mol/l and IC50 value for paraoxon was 4.00 x 10(-6) mol/l. A volume 5 mu l of sample was sufficient for the assay and the sample was applied directly without any processing. In a conclusion, a simple colorimetric biosensor for the determination of venomous compounds like organophosphorus pesticides and nerve agents was constructed and promising analytical parameters were received during its characterization.