An arrangement, a method, and a measurement indicator, configured to measure urea in a milk sample of an animal (100). The arrangement includes a reference indicator, impregnated with a halochromic substance configured to adjust colour, based on a level of hydroxide ions of a first sub milk sample; a measurement indicator, impregnated with the halochromic substance of the reference indicator, and prepared with an enzyme configured to convert urea of a second sub milk sample, into at least one chemical substance, which in turn will influence the level of hydroxide ions of the second sub sample; a sensor configured to capture a first image of the reference indicator, and a second image of the measurement indicator; and a control unit configured to determine colour difference between the images; and configured to convert the determined colour difference into urea amount in the milk sample.

Apparatus and methods for measuring a concentration of a target molecule from a biological sample are disclosed. For example, the apparatus comprises a porous pad, which is impregnated with a solution containing at least one agent and contains an unfilled capillary matrix, a housing for the porous pad, and a membrane that covers the porous pad.

Apparatus and methods for measuring a concentration of a target molecule from a biological sample are disclosed. For example, the apparatus comprises a porous pad, which is impregnated with a solution containing at least one agent and contains an unfilled capillary matrix, a housing for the porous pad, and a membrane that covers the porous pad.

Provided is a portable urea sensor which can be used under a flow condition by using a porous polytetrafluoroethylene (PTFE) membrane coated with parylene-A, which is parylene functionalized with an amine by vacuum deposition. To produce a specific electrochemical sensor signal from urea, urease, which is an enzyme hydrolyzing urea, is immobilized to a parylene-A-coated PTFE membrane by chemical crosslinking using glutaraldehyde. The urea-immobilized membranes are assembled in a polydimethylsiloxane (PDMS) fluid chamber, and a screen-printed carbon 3-electrode system is used. The success of the urease immobilization process is confirmed using scanning electronmicroscopy (SEM) and Fourier-transform infrared (FTIR) spectroscopy. The optimal concentration of urease to be immobilized to the parylene-A-coated PTFE membrane is determined to be 48 mg/mL, and the optimal number of the membranes in the PDMS chamber is determined to be 8.

Multi-use biosensors are disclosed that include enzymes that have been modified to reduce the solubility thereof; the multi-use biosensors are used to detect analytes in fluidic biological samples, and the biosensors also maintain their enzyme activity after many uses. Multi-sensor arrays are disclosed that include multiple biosensors. Also disclosed are methods of producing and using these devices.

Multi-use biosensors are disclosed that include enzymes that have been modified to reduce the solubility thereof; the multi-use biosensors are used to detect analytes in fluidic biological samples, and the biosensors also maintain their enzyme activity after many uses. Multi-sensor arrays are disclosed that include multiple biosensors. Also disclosed are methods of producing and using these devices.

Aqueous calibration or quality control reagents that include urea are disclosed; the reagents may further include at least one amino acid-containing composition to provide pH stability thereto. Methods of production and use thereof are also disclosed.

Aqueous calibration or quality control reagents that include urea are disclosed; the reagents may further include at least one amino acid-containing composition to provide pH stability thereto. Methods of production and use thereof are also disclosed.

The present subject matter provides urea biosensors as well as compositions, devices, and methods comprising such biosensors.

The present subject matter provides urea biosensors as well as compositions, devices, and methods comprising such biosensors.