2 research outputs found
Polyethylenimine Carbon Nanotube Fiber Electrodes for Enhanced Detection of Neurotransmitters
Carbon nanotube (CNT)-based microelectrodes
have been investigated
as alternatives to carbon-fiber microelectrodes for the detection
of neurotransmitters because they are sensitive, exhibit fast electron
transfer kinetics, and are more resistant to surface fouling. Wet
spinning CNTs into fibers using a coagulating polymer produces a thin,
uniform fiber that can be fabricated into an electrode. CNT fibers
formed in poly(vinyl alcohol) (PVA) have been used as microelectrodes
to detect dopamine, serotonin, and hydrogen peroxide. In this study,
we characterize microelectrodes with CNT fibers made in polyethylenimine
(PEI), which have much higher conductivity than PVA-CNT fibers. PEI-CNT
fibers have lower overpotentials and higher sensitivities than PVA-CNT
fiber microelectrodes, with a limit of detection of 5 nM for dopamine.
The currents for dopamine were adsorption controlled at PEI-CNT fiber
microelectrodes, independent of scan repetition frequency, and stable
for over 10 h. PEI-CNT fiber microelectrodes were resistant to surface
fouling by serotonin and the metabolite interferant 5-hydroxyindoleacetic
acid (5-HIAA). No change in sensitivity was observed for detection
of serotonin after 30 flow injection experiments or after 2 h in 5-HIAA
for PEI-CNT electrodes. The antifouling properties were maintained
in brain slices when serotonin was exogenously applied multiple times
or after bathing the slice in 5-HIAA. Thus, PEI-CNT fiber electrodes
could be useful for the in vivo monitoring of neurochemicals
Laser Treated Carbon Nanotube Yarn Microelectrodes for Rapid and Sensitive Detection of Dopamine in Vivo
Carbon
nanotube yarn microelectrodes (CNTYMEs) exhibit rapid and
selective detection of dopamine with fast-scan cyclic voltammetry
(FSCV); however, the sensitivity limits their application in vivo.
In this study, we introduce laser treatment as a simple, reliable,
and efficient approach to improve the sensitivity of CNTYMEs by threefold
while maintaining high temporal resolution. The effect of laser treatment
on the microelectrode surface was characterized by scanning electron
microscopy, Raman spectroscopy, energy dispersion spectroscopy, and
laser scanning confocal microscopy. Laser treatment increases the
surface area and oxygen containing functional groups on the surface,
which provides more adsorption sites for dopamine than at unmodified
CNTYMEs. Moreover, similar to unmodified CNTYMEs, the dopamine signal
at laser treated CNTYMEs is not dependent on scan repetition frequency,
unlike the current at carbon fiber microelectrodes (CFMEs) which decreases
with increasing scan repetition frequency. This frequency independence
is caused by the significantly larger surface roughness which would
trap dopamine-<i>o</i>-quinone and amplify the dopamine
signal. CNTYMEs were applied as an in vivo sensor with FSCV for the
first time, and laser treated CNTYMEs maintained high dopamine sensitivity
compared to CFMEs with an increased scan repetition frequency of 50
Hz, which is 5-fold faster than the conventional frequency. CNTYMEs
with laser treatment are advantageous because of their easy fabrication,
high reproducibility, fast electron transfer kinetics, high sensitivity,
and rapid in vivo measurement of dopamine and could be a potential
alternative to CFMEs in the future