Choline electrochemical biosensor based on MWCNT-AuNPs and MWCNT-PANI composite nanomaterials

Choline levels in the human body are indicative of diseases such as glioma, Alzheimer’s disease, and Parkinson’s disease, which is crucial in clinical diagnosis. Therefore, there is an urgent need for a method to detect choline that has potential clinical applications. A novel choline electrochemical biosensor based on choline oxidase was successfully developed, and its performance was significantly improved by modifying the composite of multi-walled carbon nanotubes and gold nanoparticles (MWCNT-AuNPs) and the composite of multi-walled carbon nanotubes and polyaniline (MWCNT-PANI). By combining the time–current method, the concentration of choline was determined based on the magnitude of the oxidation current, enabling trace-level detection of choline. The results showed that the modifying of nanomaterials on the electrode surface can improve both the conductivity and current response of the enzyme electrode. The choline oxidase/composite of multi-walled carbon nanotubes/composite of multi-walled carbon nanotubes and polyaniline and gold nanoparticles (ChOx/MWCNT-AuNPs/MWCNT-PANI) electrode showed a good linear response and a wide linear range to choline in the range of 0.033–133.330 μM. The results of the time–current indicated that our biosensor provided a higher sensitivity of 4.85 nA/μM and a lower detection limit of 0.025 μM (S/N = 3) for choline sensing. Furthermore, the sensor retained 90 % of the initial activity after 50 days. The results exhibited that the novel choline biosensor has the potential to be used for the clinical diagnosis of diseases and prevent disease recurrence, based on detecting the changes of choline level.