Ascorbic acid does not necessarily interfere with the electrochemical detection of dopamine

Abstract

It is widely stated that ascorbic acid (AA) interferes with the electrochemical detection of neurotransmitters, especially dopamine, because of their overlapping oxidation potentials on typical electrode materials. As the concentration of AA is several orders of magnitude higher than the concentration of neurotransmitters, detection of neurotransmitters is difficult in the presence of AA and requires either highly stable AA concentration or highly selective neurotransmitter sensors. In contrast to the common opinion, we show that AA does not always interfere electrochemical detection of neurotransmitters. The decay of AA is rapid in cell culture medium, having a half-time of 2.1 hours, according to which the concentration decreases by 93% in 8 hours and by 99.75% in 18 hours. Thus, AA is eventually no longer detected by electrodes and the concentration of neurotransmitters can be effectively monitored. To validate this claim, we used unmodified single-wall carbon nanotube electrode to measure dopamine at physiologically relevant concentration range (25–1000 nM) from human midbrain organoid medium with highly linear response. Finally, AA is known to affect dopamine oxidation current through regeneration of dopamine, which complicates precise detection of small amounts of dopamine. By designing experiments as described here, this complication can be completely eliminated.

Electrochemical Behavior of Different Diffusional Redox Probes on a Porous Acetylene Black Electrode: Mass Transport Modes and Electrostatic Effects

“…The cation exchange properties of Nafion and its blocking effect toward anions are well known. For instance, Nafion is used to block out the anionic (negatively charged) ascorbate and accumulate the cationic (positively charged) dopamine in sensing electrodes. − In the same system, the accumulation (trapping) effect of the Nafion and the subsequent signal enhancement have also been demonstrated. Furthermore, in the AB and Nafion IPA solution, aggregates between AB and Nafion are formed with sulfonic groups heading toward AB, as stated by Conde and Chaparro .…”

SMN deficiency perturbs monoamine neurotransmitter metabolism in spinal muscular atrophy

“…Therefore, the clinical and biochemical information available during the longitudinal analysis was not always based on a strictly uniform sample size (Supplementary Tables 7-9), and no further parameters detailing the clinical state of the patients were available. For the same reasons, this study was not designed for DA determination, which is highly susceptible to oxidation when not protected by antioxidants at the time of collection 69,70 .…”

Engineering FeOOH/Fe2O3@Carbon Interfaces With Biomass‐Derived Carbon Nanodot/Iron Colloids for Efficient Redox‐Modulated Dopamine Voltammetric Detection

“…However, in the presence of DA + 100× AA, the I PA of DA and AA are indistinguishable, and the value of DA's I PA is 257.85 % greater than that of only DA (Figure S19F). According to reference [83] this could be due to two factors: (i) both chemicals have similar redox potential (which is true based on Figure S19F) and/or (ii) because AA is a strong antioxidant, it reduces oxidized-DA back to DA which increases the DA flux on the β-FeOOH/α-Fe 2 O 3 /2.0-27@sp 2 -C surface leading more oxidation and higher current. Fortunately, this limitation can be mitigated by coating a layer of cation exchange membrane (e. g., nafion) on the surface of β-FeOOH/ α-Fe 2 O 3 /2.0-27@sp 2 -C. The idea behind this approach is to shrink the diffusion layer of DA on β-FeOOH/α-Fe 2 O 3 /2.0-27@sp 2 -C while increasing that of AA via ion exchange.…”