Design of amperometric urea biosensor based on self-assembled monolayer of cystamine/PAMAM-grafted MWCNT/Urease

In this work, we report novel amperometric urea biosensor based on immobilization of Urease enzyme onto self-assembled polyamidoamine grafted multiwalled carbon nanotube (MWCNT-PAMAM) dendrimers (from G1, first generation up to G5) on Au electrode. Bio-sensing electrode's performance parameters such as optimum pH, temperature, and applied potential together with reproducibility were investigated. The electrode based on fifth generation of MWCNT-PAMAM and urease enzyme showed excellent performance in urea detection at an applied potential of 0.45 V with short response time of 3 s, wide linear range of 1-20 mM, detection limit of 0.4 mM, and sensitivity of 6.6 nA/mM. No significant response was detected in the presence of possible interferon molecules. Non-diluted human blood plasma has been used for real sample application where electrode showed excellent performance in urea detection.