Biology subjects

Khot, G.

Publications and source records attributed to Khot, G..

4 recordsLinked to original sources

bioRxiv2021

Simultaneous Detection of Dopamine and Serotonin on Carbonized Micropipette Decorated with Carbon Nanotubes

Graphite-based materials, like pyrolyzed carbon electrodes, are widely used as implantable electrochemical sensors, for the detection of neurotransmitters, neuromodulators, and gaseous species, thanks to their strong mechanical properties, superior electron-transfer kinetics, and in-vivo stability. Electrochemical properties of graphite can be improved by coating them with carbon nanotubes (CNTs) which improves sensitivity, selectivity, and resistance to biofouling. Although several types of electrodes have been developed to detect biologically relevant targets like monoamines, multiplexed sensing of dopamine and serotonin is not yet widely available. Herein we introduce pyrolyzed carbon electrodes coated with CNTs for fast scan cyclic voltammetry for simultaneous detection of dopamine and serotonin with a sensitivity of 52{+/-}8nA/M and 5{+/-}17nA/M, respectively. Serotonin shows a broad oxidation peak at 0.68V{+/-}0.12V. When dopamine and serotonin are probed simultaneously at 10 Hz, dopamine oxidizes at 0.1V{+/-} 0.1 and serotonin oxidizes at 0.78V{+/-}0.12 and dopamine reduces at -0.35V{+/-}0.1 and serotonin at 0.1V{+/-}0.2 V. Thus the sensors shows discrimination between dopamine and serotonin and are suitable for simultaneous detection of these monoamines.

biochemistry↗

bioRxiv2021

Electrochemical Detection of Adrenaline and Hydrogen Peroxide on Carbon Nanotube Electrodes

Adrenaline and hydrogen peroxide have neuromodulatory functions in the brain. Considerable interest exists in developing electrochemical sensors that can detect their levels in vivo due to their important biochemical roles. Challenges associated with electrochemical detection of hydrogen peroxide and adrenaline are that the oxidation of these molecules usually requires highly oxidising potentials (beyond 1.4 V vs Ag/AgCl) where electrode damage and biofouling are likely and the signals of adrenaline, hydrogen peroide and adenosine overlap. To address these issues we fabricated pyrolysed carbon electrodes coated with oxidised carbon nanotubes (CNTs). Using these electrodes for fast-scan cyclic voltammetric (FSCV) measurements showed that the electrode offers reduced overpotentials compared with graphite and improved resistance to biofouling. The Adrenaline peak is reached at 0.75({+/-}0.1) V and reduced back at -0.2({+/-}0.1) V while hydrogen peroxide is detected at 0.85({+/-}0.1) V on this electrode. The electrodes are highly sensitive with a sensitivity of 16nA {micro}M-1 for Adrenaline and 11nA {micro}M-1 for hydrogen peroxide on an 80 {micro}m2 electrode. They are also suitable to distinguish between adrenaline, hydrogen peroxide and adenosine thus these probes can be used for multimodal detection of analytes.

neuroscience↗

bioRxiv2021

Principles of Dopamine Binding to Carbon Surfaces

Fast Scan Cyclic Voltammetry (FSCV) combined with carbon electrodes is considered as the gold standard method for real-time detection of oxidizable neurotransmitters. The bioinert nature, rapid electron transfer kinetics and long-term stability make carbon an attractive material for probing brain electrochemistry. Herein, we first demonstrate a rapid fabrication process of carbonized nanopipettes and subsequently perform experimental measurements and theoretical simulations to study mechanisms of dopamine binding on carbonized surfaces. To explain the kinetics of dopamine oxidation on carbonized electrodes we adapted the electron-proton transfer model originally developed by Compton and found that the electron-proton transfer model best explains the experimental observations. We further investigated the electron-proton transfer theory by constructing a Density Function Theory (DFT) for visualization of dopamine binding to graphite-like surfaces consisting of heteroatoms. For graphite surfaces that are capped with hydrogen alone, we found that dopamine is oxidized, whereas, on graphite surfaces doped with heteroatoms such as nitrogen and oxygen, we found deprotonation of dopamine along with oxidation thus validating our experimental and theoretical data. These observations provide mechanistic insights into multistep electron transfer during dopamine oxidation on graphite surfaces. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=186 SRC="FIGDIR/small/457508v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@8bee9corg.highwire.dtl.DTLVardef@de66ecorg.highwire.dtl.DTLVardef@1373032org.highwire.dtl.DTLVardef@3d61d0_HPS_FORMAT_FIGEXP M_FIG A: Pictorial view of the experimental setup of carbonized electrodes. The application of waveform causes the oxidation of dopamine. B. Background subtracted voltammogram of dopamine, wherein the waveform applied is -0.4V to 1.3V and cycled back at -0.4V at 200 V s-1 at 10 Hz. C: A hotspot showing the oxidation and reduction of dopamine, wherein two distinct redox spots can be seen. The first redox spot can be seen at 0.0V and the second one at 0.5V. Thus showing a multistep electron transfer for dopamine. D: A DFT model for dopamines interaction with graphite surfaces doped with nitrogen atoms. Oxidation of oxygen (red) can be seen with loss of protons. C_FIG

biochemistry↗

bioRxiv2021

Carbon Nanotube Electrodes for Electrochemical Detection of Dopamine

Carbon nanotubes (CNTs) are suited for neurochemistry because of their biological inertness, ability to withstand biofouling, and superior electron transport kinetics. Dopamine, the canonical monoaminergic neuromodulator, contributes to reward, cognition and attention, however, its detection in real-time is challenging due to its low basal concentration in the brain (100nM L-1). In our present work, we fabricate pyrolytic carbon electrodes and perform a CNT coating to improve the electrochemical kinetics of dopamine. Upon CNTs coating, dopamine shows a sensitivity of 9{+/-}18nA/M for a cylindrical electrode having a mean surface diameter of 8{+/-}4m. Increasing the scan frequency from 10-100 Hz shows that dopamine electron transfer kinetics improves; wherein dopamine is oxidized at 0.35{+/-}0.09V and reduced to -0.10{+/-}0.05V for 10 Hz. Increasing the frequency results in a shift of oxidation peak towards the anodic region, wherein dopamine oxidizes at 0.08{+/-}3V and reduces at -0.1{+/-}0.05V for 100 Hz, thus showing that dopamine redox is reversible which can be attributed to the superior electron transport kinetics of CNTs. The sensor was able to distinguish dopamine signals against other neurochemicals like serotonin and foulant 3,4-Dihydroxyphenylacetic acid (DOPAC). The minimum chemical detection that can be performed using these nanopipettes is 50{+/-}18nM L-1, which is well below the physiological concentrations of dopamine in the brain. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=185 SRC="FIGDIR/small/457511v1_ufig1.gif" ALT="Figure 1"> View larger version (34K): org.highwire.dtl.DTLVardef@bf710aorg.highwire.dtl.DTLVardef@966bcforg.highwire.dtl.DTLVardef@1800530org.highwire.dtl.DTLVardef@1d4a37e_HPS_FORMAT_FIGEXP M_FIG A: Pictorial view of background-subtracted voltammetry. The waveform used was -0.4V to 1.3 V and cycled back to -0.4V at 10 Hz. B: The voltammogram was converted as a 2-D representation, into current, voltage, and repetition to understand the dopamine oxidation. C: Background subtracted voltammetry for dopamine using 100 Hz waveform. D: The 2-D representation of current, voltage, and repetition. C_FIG

biochemistry↗