Electrochemical Aptasensor for Detection of Dopamine

Abstract

This work presents a proof of concept of a novel, simple, and sensitive method of detection of dopamine, a neurotransmitter within the human brain. We propose a simple electrochemical method for the detection of dopamine using a dopamine-specific aptamer labeled with an electrochemically active ferrocene tag. Aptamers immobilized on the surface of gold screen-printed gold electrodes via thiol groups can change their secondary structure by wrapping around the target molecule. As a result, the ferrocene labels move closer to the electrode surface and subsequently increase the electron transfer. The cyclic voltammograms and impedance spectra recorded on electrodes in buffer solutions containing different concentration of dopamine showed, respectively, the increase in both the anodic and cathodic currents and decrease in the double layer resistance upon increasing the concentration of dopamine from 0.1 to 10 nM L −1 . The high affinity of aptamer-dopamine binding (KD ≈ 5 nM) was found by the analysis of the binding kinetics. The occurrence of aptamer-dopamine binding was directly confirmed with spectroscopic ellipsometry measurements.Chemosensors 2020, 8, 28 2 of 11 done on the electrochemical detection of dopamine and other neurotransmitters [2,3]. Dopamine can be very easily detected in an aqueous solution by electrochemical methods such as cyclic voltammetry since dopamine undergoes electrochemical oxidation. However, a major issue is the selectivity since complex matrices such as blood contain a range of other oxidizable compounds such as urate or ascorbate which would also generate signals, leading to inaccurate readings. Selectivity towards dopamine is therefore required.A wide range of electrode materials have been proposed to increase the selectivity of dopamine detection [2,3]. A few recent examples include the use of materials such as Nafion combined with graphite [4] or multi-walled carbon nanotubes [5] to improve the selectivity towards dopamine. Other researchers have utilized graphene-modified screen-printed electrodes [6] or graphene aerogels [7] as substrates for the selective determination of dopamine. Composites of carbon nanotubes and graphene oxide could be used to determine dopamine, nitrate, ascorbate, and urate [8]. Metal nanoparticles have also been utilized, for example palladium nanoparticles combined with graphene [9], which were used as a base of electrochemical determination of dopamine whereas a gold nanoparticle/DNA/polymer composite could be used for the simultaneous determination of dopamine, uric acid, guanine, and adenine [10]. Composites of gold nanoparticles with conducting polymers have also been used for the selective determination of dopamine [11]. Boron-doped carbon nanotubes could be used to determine levels of dopamine and ephedrine in the presence of urate [12]. Composites of graphene oxide with Bi 2 S 3 nanorods were used for the electrochemical determination of dopamine [13], and arrays of cylindrical gold nanoelectrodes could be used for both the detection of dopamine an...

Electrochemical Detection of Prostate Cancer Biomarker PCA3 Using Specific RNA-Based Aptamer Labelled with Ferrocene

“…In both cases, the sensitivity is very high and approaching ppt levels. The achieved high sensitivity here in detecting PCA3 is very similar to the sensitivities of other electrochemical aptasensors reported earlier [43][44][45]. Negative controls test on binding BSA to anti-PCA3 aptamers were carried out but showed no response.…”

“…Another approximation used in the binding kinetics analysis is applying a single binding site assumption to a complex binding process between the aptamer and PCA3 which involves interactions between several nucleotides. However, the proposed approach has been successfully used in similarly complex systems of antibody-antigen interactions [48,49] and in our previous works on aptamer-based biosensors [45,50].…”

“…Conformational change brings the redox label closer to the electrode resulting in a subsequent increasing in charge transfer. This approach has been successfully adapted for electrochemical detection of mycotoxins, particularly ochratoxin A, in food analysis [43] and has been applied to the detection of heavy metal ions (Hg 2+ and Pb 2+ ) in water [44] and the in-vitro detection of dopamine [45].…”

Recent Advances in In Vivo Neurochemical Monitoring

“…Andrews’ group constructed flexible aptamer-field-effect-transistors for DA and 5-HT sensing with a 10 fM LOD [ 150 ]. However, most E-AB sensor work focuses on in vitro development and analysis only using serum or blood samples [ 151 , 152 , 153 ]. This is presumably due to the instability of E-AB sensors in vivo that results from the degradation of the recognition aptamer, and non-specific interferant adsorption on the sensor’s surface may cause significant drift [ 154 ].…”

From Small Molecules toward Whole Cells Detection: Application of Electrochemical Aptasensors in Modern Medical Diagnostics

“…The analysis was conducted in flow injection mode, where the aptasensor response to dopamine was within ≈1 s (almost instantly after the dopamine injection), the sensitivity 67 ± 1 nA μM−1 cm −2 , and the dopamine lower limit of detection (LOD) was 62 nM ( Figure 7 ). Nonetheless, despite numerous electrochemical dopamine aptasensors mentioned in the literature [ 92 , 93 , 94 , 95 , 96 ], still, the greatest challenge is its accurate measurement in body fluids. This is related to numerous neurochemical events after the dopamine (or other neurotransmitters) release, which lead to its transformation at the time-scale of a few seconds or less (the dopamine lifetime ranges from 100 to 0.05 s and depends on the current state of the organism).…”