The development of a highly sensitive urea sensor due to the formation of an inclusion complex between urea and sulfonated-β-cyclodextrin

•A novel urea sensor was developed using polypyrrole to entrap the urease enzyme.•The presence of the urease enzyme was confirmed using SEM and EDX analysis.•The urea sensor doped with SCD has a sensitivity of 5.79 μC μM−1 towards urea.•The formation of an inclusion complex between SCD and urea was investigated.•A 1:1 inclusion complex was established with a formation constant of 2745 + - 300 M−1.

A highly sensitive urea sensor was developed by incorporating the urease enzyme (Urs) into a polypyrrole film (PPy) in one simple electropolymerisation step, using a sulfonated-β-cyclodextrin dopant. This PPy-Urs-SCD film has a superior sensitivity of 5.79 μC μM−1 and detection in the region of 1.0 × 10−10 M urea, which is greater than other urea sensors reported in the literature. This is due to the formation of an inclusion complex between urea and a sulfonated-β-cyclodextrin host in an aqueous solution, which was established using electrochemical techniques. Cyclic voltammetry was used to investigate the effect of an excess concentration of the sulfonated-β-cyclodextrin on the currents recorded for urea. A clear reduction in the current was observed upon the addition of the sulfonated-β-cyclodextrin. The formation constant, Kf, was computed as 2745 ± 300 M−1, indicating the formation of a relatively strong inclusion complex. In addition, a 1:1 stoichiometry for the inclusion complex was deduced from a Job's plot analysis.

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