A metal-organic zeolitic framework with immobilized urease for use in a tapered optical fiber urea biosensor.

A tapered single-mode coreless single-mode (SCS) structure with high sensitivity for sensing refractive index is described. In order to achieve high specificity of optical biosensors, here enzyme capsulation film was achieved by embedding urease in zeolitic imidazolate framework (ZIF-8/urease) through in situ growth approach on the coreless fibers. Determination of urea is achieved through online monitoring of its binding to the urease in zeolitic imidazolate framework. Refractive index change result in wavelength shifts of the optical fiber biosensor. The resonance wavelength exhibits a good linear relationship with urea concentration in the range of 1 to 10 mM with detection limit of 0.1 mM and sensitivity of 0.8 mM/RIU (refractive index unit) if operated with broadband light ranging from 1525 nm to 1590 nm. Final assessment of optical biosensor in real sample was performed where excellent performance in terms of sensitivity and selectivity was observed. Schematic representation of experimental setup and mechanism for urea detection. A tapered single-mode coreless single-mode (SCS) structure is placed between a broadband light source ranging (BBS) and optical spectrum analyzer (OSA). ZIF-8/urease composites are applied as a recognition layer for urea detection.