Direct enzyme immobilization on SPEs for electrochemical pesticide detection in olive oil, utilizing laser induced forward transfer

Electrochemical biosensors are increasingly used for the detection of various analytes (pesticides, mycotoxins etc.) in food, due to the rapid and reliable detection that can be achieved without the need for expensive instrumentation equipment, skilled personnel and long time-to–result that is required by conventional analytical techniques. Laser Induced Forward Transfer (LIFT) bio-printing in combination with an all- in- one enzyme solution (a solution that includes the enzyme mixed with signal-enhancing carbon-based materials suspended in a polymer matrix) provides new possibilities for biosensor pesticide detection in olive oil as it delivers direct and accurate immobilization of enzyme solution with high special resolution and the ability to print in significantly smaller electrode surfaces for less material waste. Here, we report the use of LIFT technique, utilizing a 355 nanosecond laser for the highly precise, direct deposition and immobilization of Acetylcholinesterase (AChE) on screen printed electrode (SPE) surfaces. Due to the high impact pressure of the transferred droplets at the receiver substrate, the physical adsorption of the enzyme mixture onto the surface is enhanced, improving the electrochemical communication with the SPE. The inhibitory effect of the analytes on the AChE biosensor was evaluated amperometrically by determining the decrease in the current obtained for the oxidation of the thiocholine produced by the enzyme upon incubation with pesticide solutions, and a LoD below the legislation limit (10 ppb) was achieved. Furthermore, the biosensor’s performance was assessed in olive oil samples spiked with carbofuran and chlorpyrifos, following an optimized pretreatment protocol, with very satisfactory recovery values.