Communication-Carbon Nanotube Fiber Microelectrodes for High Temporal Measurements of Dopamine

Abstract

Carbon nanotube (CNT) yarn and fiber-microelectrodes were developed for neurotransmitter detection using fast scan cyclic voltammetry (FSCV). Fibers were made by suspending CNTs in acid/surfactant and extruding into acetone/polyethyleneimine (PEI) and compared to a CNT yarn. They were FSCV frequency independent for dopamine up to 100 Hz. With faster frequencies, up to 500 Hz, high currents are maintained, which allows a 2 ms sampling rate for FSCV, compared to 100 ms. CNT fibers have rough surfaces which trap dopamine and dopamine-o-quinone (DOQ), creating more reversible CVs. CNT yarns and fibers are beneficial for high sensitivity, rapid measurements of neurotransmitters.

Figure 1:. SEM Images of CNT Fibers and Yarn.

(A) Cross-section of a CNT yarn microelectrode. (B) SEM image of a PEI CNT fiber end. Thin whiskers of individual CNTs protrude from the bundles in the cross-section. (C). SEM of Acid Spun CNT fiber.

Figure 2:

Frequency Response for 1 μM dopamine (400 V/s). Left: CVs at 10 Hz and 90 Hz repetition rates. Middle: Current with increasing FSCV frequency during repeated injections of dopamine. Right: Current vs time traces showing the temporal response. A. CFMEs (current drops with frequency). B. CNT Yarns are frequency independent (R²=.002). C. PEI-CNT fiber ME are frequency independent (R² = .007). D. Acid-CNT fiber MEs are frequency independent (R² = .074). n=4–6. The i vs t plots show that the rapid temporal response is maintained at high frequencies.

Figure 3:

High Temporal Resolution Measurements. Example CVs of 1 μM dopamine at 2000 V/s at 10 Hz and 500 Hz repetition rates at A. CFMEs, B. CNT yarn MEs and C. CNT-PEI fiber MEs.