A new atrazine pesticide potentiometric biosensor was described using urease biomolecules immobilized onto the insulator-semiconductor electrode and different additional materials such as glutaraldehyde as a cross-linking agent, bovine serum albumin, coated nanoparticles (Fe 3 O 4 ), cationic poly(allylamine hydrochloride) and anionic poly(sodium 4-styrenesulfonate) polyelectrolytes. The effect of atrazine molecules on the activity of free and immobilized urease was studied using the ion selective electrodes (ISEs) and capacity-potential measurements C(V). The sensitivity of the modified bioelectrode to urea addition was evaluated by the capacitance method via the relationship between the evolution of the flat band potential DV FB and the urea concentration for values ranging from 23 to 0.04 mM. The detection of atrazine in solution was performed via its inhibiting action on the urease biosensor. An incubation time of 30 min was chosen to study the inhibition effect of atrazine for different concentrations on the urease biosensor. Under optimal experimental conditions, the enzymatic activity, the inhibition process and the analytical characteristics of the resulting ENFEC (Enzyme Field effect capacitive) system were investigated. As a result, the detection limit of atrazine via the inhibition of urease activity was about 0.13 mM with a dynamic concentration range from 10 À2 to 10 À7 M.

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In this work we describe a new urea biosensor, based on the immobilization of bacteria, Proteus mirabilis on gold electrode. To improve the stability of the bio-system, additional materials were used such as functionalized Fe 3 O 4 nanoparticles (NPs), cationic (PAH), anionic (PSS) polyelectrolytes, Bovine Serum Albumin (BSA) and glutaraldehyde as a cross-linking agent. The electrochemical performances of the developed bacteria biosensor was evaluated using the electrochemical impedance spectroscopy (EIS) and cyclic voltammetry measurements. The adhesion of the bacteria cell on gold electrode was evaluated using contact angle measurements. The morphology of bacteria and its interaction with Fe 3 O 4 nanoparticles were evaluated with the atomic force microscopy (AFM). As a result, a sensitive, stable and reproducible urea biosensor was developed.

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