Detection of urea in milk by urease-inorganic hybrid nanoflowers combined with portable colorimetric microliter tube.

A simple one-pot green synthesis method was used to prepare urease-inorganic hybrid nanoflowers (UE-HNFs), which had a high surface-to-volume ratio to improve enzyme catalytic efficiency and make urease reusable. A portable colorimetric microliter tube based on urease-inorganic hybrid nanoflowers (UE-HNFs-PCMT), as an urea colorimetric biosensor, was developed for determining urea concentration in milk. The combination of urea colorimetric biosensor and a smartphone is used for capturing the colour change of milk after reaction. There was a good linear relationship between colour intensity of the image (Δ intensity) and urea concentration (43-600 mg L), with a detection limit of 12.81 mg L. UE-HNFs-PCMT has the advantages of no need for complex equipment, easy operation, reusability, low detection cost, good portability, and environmental friendliness and can achieve urea detection in milk.