Electrochemical Proteus vulgaris whole cell urea sensor in synthetic urine

Abstract

An electrochemical whole cell Lab-on-a-Chip sensor for the detection of urea in synthetic urine has been developed. Urea was indirectly monitored by the electrochemical ammonia oxidation liberated by the microbial P. vulgaris microorganism surface membrane reaction. For this, a custom-made platinum miniature electrode platform utilizing lift-off photolithography technique and coupled with a 3D printed casing was fabricated. A P. vulgaris pellet was drop casted on the Pt working electrode surface and exposed to different urea concentrations in synthetic urine. The electrochemical determination of urea was done via the ammonia oxidation reaction. In presence of P. vulgaris, our results showed a relationship between the ammonia oxidation peak current density (from 0.5 to 5.0 μA/cm2) and the urea concentration (from 0.01 M to 0.1 M) in synthetic urine aqueous solutions. The sample volumes analyzed were 80 μL and 100 μL of urea in synthetic urine at pH 8.0. The former presented less variability and higher sensitivity. The as-prepared microchips were characterized by scanning electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy and cyclic voltammetry to determine its surface composition, modification, and robustness.

Keywords

• Proteus vulgaris
• Urea
• Electrochemical sensor
• Synthetic urine
• Ammonia