Immobilized pigeon pea urease on chitosan-PEG biocomposite for concurrent urea sensing in milk and blood samples

Abstract

The ubiquitous hydrolytic enzyme urease converts urea into ammonia and carbon dioxide, making it an essential indicator for dairy product quality and kidney health. We developed a biocomposite sensor to meet this diagnostic necessity. This innovation strategically incorporates pigeon pea seed urease into chitosan-PEG. We verified our predicted model with a 91.30 % immobilization efficiency via our thorough process. The immobilized urease showed strong catalytic activity, with a V<inf>max</inf> of 3194 μmol/min/mg and a K<inf>m</inf> of 0.373 mM. Optimal activity was observed at 90 °C and pH 8.0. Additionally, it exhibited exceptional operational stability, maintaining 56 % activity over 200 days at 4 °C and 60 % reusability over 11 cycles. The sensor showed a wide linear detection range (5–400 mg/dL) with high sensitivity (LOD 3.10 (±0.155) mg/dL, LOQ 10.36 (±0.510) mg/dL). Its high selectivity (K<inf>sel</inf> < 0.08) ensures precise urea detection in complex milk and blood matrices. This stable and reproducible biocomposite is a breakthrough in dairy and healthcare analytical tools. © 2025 Elsevier Ltd