Urease covalently immobilized on cotton-derived nanocellulose-dialdehyde for urea detection and urea-based multicomponent synthesis of tetrahydro-pyrazolopyridines in water

]pyridines (THPPs) in water. This new environment-friendly urea sensor showed 90% preservation of the enzyme activity after the six cycles of reuse in enzymatic reactions, while its catalytic activity in the reaction of benzaldehyde, hydrazine hydrate, and alkyl acetoacetate with urea instead of hygroscopic ammonium salts did not change significantly after the sixth run. Detection and production of ammonia by a bio-compatible sensor and catalyst under mild conditions are features of this new green protocol.