Tri-enzyme functionalized ZnO-NPs/CHIT/c-MWCNT/PANI composite film for amperometric determination of creatinine

A new zinc oxide nanoparticles/chitosan/carboxylated multiwall carbonnanotube/polyaniline (ZnO-NPs/CHIT/c-MWCNT/PANI) composite film has been synthesized on platinum (Pt) electrode using electrochemical techniques. Three enzymes, creatinine amidohydrolase (CA), creatine amidinohydrolase (CI) and sarcosine oxidase (SO) were immobilized on ZnO-NPs/CHIT/c-MWCNT/PANI/Pt electrode to construct the creatinine biosensor. The enzyme electrode was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and electrochemical impedance spectroscopy (EIS). The enzyme electrode detects creatinine level as low as 0.5 μM at a signal to noise ratio of 3 within 10 s at pH 7.5 and 30 °C. The fabricated creatinine biosensor showed linear working range of 10-650 μM creatinine with a sensitivity of 0.030 μA μM−1 cm−2. The biosensor shows only 15% loss of its initial response over a period of 120 days when stored at 4 °C. The fabricated biosensor was successfully employed for determination of creatinine in human blood serum.