Detection of neurochemicals with enhanced sensitivity and selectivity via hybrid multiwall carbon nanotube-ultrananocrystalline diamond microelectrodes

Abstract

Abnormal neurochemical signaling is often the underlying cause of brain disorders. Electrochemical microsensors are widely used to monitor neurochemicals with high spatialtemporal resolution. However, they rely on carbon fiber microelectrodes that often limit their sensing performance. In this study, we demonstrate the potential of a hybrid multiwall carbon nanotube (MWCNT) film modified boron-doped ultrananocrystalline diamond (UNCD) microelectrode (250 μm diameter) microsensor for improved detection of dopamine (DA) in the presence of common interferents. A series of modified microelectrodes with varying film thicknesses were microfabricated by electrophoretic deposition (EPD) and characterized by scanning electron microscopy, x-ray photoelectron spectroscopy, electrochemical impedance spectroscopy (EIS) and silver deposition imaging. Using cyclic voltammetry, the 100-nm "thin" film microelectrode produced the most favorable combination of DA sensitivity value of 36 ±2% μA/μM/cm 2 with a linear range of 33 nM to 1 μM and a limit of detection (LOD) of 9.5 ± 1.2% nM. The EIS spectra of these microelectrodes revealed three regions with inhomogeneous pore geometry and differing impedance values and electrochemical activity, which was found to be film thickness dependent. Using differential pulse voltammetry, the modified microelectrode showed excellent selectivity by exhibiting three distinct peaks for the DA, serotonin and excess ascorbic acid in a ternary mixture. These results provide two key benefits: first, remarkable improvements in DA sensitivity (>125-fold), selectivity (>2000-fold) and LOD (>180-fold), second, these MWCNTs can be selectively coated with a simple, scalable and low cost EPD process for highly multiplexed microsensor technologies. These advances offer considerable promise for further progress in chemical neurosciences.

Recent Advances in In Vivo Neurochemical Monitoring

“…In their study, DPV was able to distinguish the oxidation peaks of DA and 5-HT at 0.15 and 0.36 V, respectively [ 45 ]. Similar studies, both in vitro and in vivo, using microelectrodes and DPV to selectively detect neurochemicals have been reported [ 46 , 47 , 48 , 49 ].…”

Recent Advances in Electrochemical and Optical Sensing of Dopamine

“…The work presented by Tan et al (2018) has added a lot to key metrics of DA microsensor including selectivity, sensitivity, detection limit and signal to noise ratio [116]. They demonstrated the role of the hybrid microelectrode in improvement the sensing performance of DA microsensor in the presence of SE and AA.…”

Progress in electrochemical detection of neurotransmitters using carbon nanotubes/nanocomposite based materials: A chronological review

“…This electrode was used for the detection of DA and UA in a DPV experiment with LOD of 1.36 and 33.03 nM, respectively. This LOD is much lower than the value reported by Tan et al [161] ILs are known to possess high ionic conductivity and when used in the design of sensors enhances the electrocatalytic activity of the modified electrode. Therefore, without doubts the presence of IL such as 1-butyl-3-methylimidazoliumtetrafluoroborate and 1butyl-3-methylimidazoliumhexafluoroborate (BMIMBF 4 and BMIMBF 6 ) in a SWCNTs with large surface area and conductivity would give rise to a very sensitive sensor.…”

“…To mitigate this deficiency, Tan et al designed a MWCNTs modified ultra-nanocrystalline diamond (UNCD) microelectrode array by electrophoretic deposition for DA and SE detection. [161] This in part was an attempt to control the CNTs thickness and benefit from the high conductivity of MWCNT and the low background current and biocompatibility of the UNCD film. The modified UNCD microelectrode had a much higher DA peak current in a CV experiment than the unmodified microelectrode.…”