Ambient Electrospray Deposition: an Efficient Technique to Immobilize Laccase on cheap electrodes with unprecedented Reuse and Storage Performances

The Electrospray Ionisation (ESI), a well established technique widely used to produce beams of biomolecules in mass spectrometry (ESI-MS), can be used for ambient soft landing of biomolecules, as enzymes, on a specific substrate[1,2]. In this work we show how the ambient electrospray deposition (ESD) technique can be successfully exploited for manufacturing a new promising green friendly electrochemical amperometric Laccase based biosensor with unprecedented reuse and storage performance. These biosensors have been manufactured by spraying a laccase solution of 2μg/μL at 20% of methanol on a commercial carbon screen printed electrode (C-SPE) using a custom ESD set-up[3]. The laccase-based ESD biosensor has been tested for the detection of catechol compound in the linear range 2–100 μM, with a limit of detection of 1.7 μM, without interference from cadmium, chrome, arsenic and zinc and without any memory effects, but showing a matrix effect in lake and well water. The ESD biosensor shows enhanced performances compared to the ones fabricated with other immobilization methods, like e.g. dropcasting. Indeed it retains a 100% activity up to two month of storage at ambient conditions without any special care and a working stability up to 63 measurements on the same electrode just prepared and 20 on one year old electrode subjected to redeposition together with a 100% resistance to use of the same electrode in subsequent days[4]. The ESD method appears to be a one-step, environmentally friendly method allowing deposition of the bio-recognition layer without using any additional chemicals. The promising results in terms of storage and working stability obtained also with lactate oxidase enzyme5, suggest these improvements should be attributed to the ESD immobilization technique rather than to the peculiarities of the bioreceptor.