Enzymatic biosensor for insecticides detection

Abstract

The detection of organophosphoric insecticides, in a simple manner was made using impedimetric enzyme biosensors, which allow determination in sub-micromolar concentration ranges. This type of measurement applies for monitoring of biocatalytic reactions based on irreversible inhibition of the enzyme (acetylcholinesterase). The reaction involves generation of charged species, which leads to a global change in the ionic composition of the tested solution.Our work has been focused on the development of an impedimetric microsensor for direct detection of dichorvos, because this kind of biosensor presents a number of advantages such as: miniaturized electrodes based on gold thin film; easy production using standard microtechnology; low cost; no reference electrode required; no light sensitivity and differential mode measurements possibile allowing elimination of interferences. In addition, dichlorvos is targeted to be detected considering that the commonest poisoning today is due to: Methyl Parathion (metacid), Dichorvos (Nuvan), Zinc Phosphide and Aluminium Phosphide (Celphos). The biosensor with interdigitated electrodes and immobilized acetylcholinesteraze (AChE) measures the impedance of the layer adjacent to the electrode surface. The impedimetric measurement consists of determining the conductivity and capacitance of the solution between two interdigitated electrodes. The chemistry of deposited enzymatic layer (concentration, enzymatic activity measuring, deposition protocol), the immobilization technique for AChE, the fabrication technique and the electrical characteristiques of the enzymatic sensor have been studied. AChE immobilization was performed by ionic adsorption on polyethylenglycol (PEG) bio-polymeric substrate, by including in the gel. The functionalized electrodes deposited with biomaterial were inserted into the microfluidic channels and tested from electrical andmicrofluidic point of view, achieving the micro-bio integration. Insertion of electrolyte plus acetilcholine into the channels leads to activation of the enzyme and the measurements are realized under the strict control of temperature and pH. The response time is about 10 minutes.