Electrochemical sensing platform amplified with a nanobiocomposite of L-phenylalanine ammonia-lyase enzyme for the detection of capsaicin

•Novel nanocomposite of L-phenylalanine ammonia-lyase enzyme for the detection of capsaicin•PAL/Nafion/MWCNTs/Pt-E promote the electron transfer and provide enhanced performance.•Ultrasensitivity and selectivity for capsaicin determination.

The present study involves the development of a sensitive electrochemical biosensor for the determination of capsaicin extracted from chilli fruits, based on a novel signal amplification strategy using enzyme technology. For the first time, platinum electrode modified with multiwalled carbon nanotubes where phenylalanine ammonia-lyase enzyme was immobilized using nafion was characterized by attenuated total reflectance infrared spectroscopy, transmittance electron microscopy and thermo-gravimetric analysis supported by computational methods. Cyclic and differential pulse voltammetry measurements were performed to better understand the redox mechanism of capsaicin. The performance of the developed electrochemical biosensor was tested using spiked samples with recoveries ranging from 98.9 to 99.6%. The comparison of the results obtained from bare and modified platinum electrodes revealed the sensitivity of the developed biosensor, having a detection limit (S/N=3) of 0.1863 µg mL−1 and electron transfer rate constant (ks) of 3.02 s−1. Furthermore, adsorption and ligand-enzyme docking studies were carried out to better understand the redox mechanisms supported by density functional theory calculations. These results revealed that capsaicin forms hydrogen bonds with GLU355, GLU541, GLU586, ARG and other amino acids of the hydrophobic channel of the binding sites thereby facilitating the redox reaction for the detection of capsaicin.