Phasic oxygen dynamics confounds fast choline-sensitive biosensor signals in the brain of behaving rodents
- Bernstein Center for Computational Neuroscience, Faculty of Medicine, Ludwig-Maximilians Universität München, Germany
Figures
Figure 1 with 1 supplement
TACO sensor design and response properties.
(A) Schematics depicting the multichannel biosensor design, including the assembly used in in vitro and head-fixed recordings (bottom). HS: head-stage. (B) Voltammogram showing H2O2 sensitivities of …
Figure 1—figure supplement 1
Effect of platings on platinum electrode sensitivity to H2O2.
Normalized H2O2 sensitivity of Pt/Ir disc electrodes (n = 6, data from our previous sensor design [Santos et al., 2015]), gold-plated Pt/Ir tetrode sites (n = 7) and gold/platinum-plated tetrode …
Figure 2 with 2 supplements
TACO sensor provides a highly sensitive and selective measurement of COA in freely behaving animals.
(A) Left panel shows a simplified diagram of the electronic circuits in freely moving recordings. The amperometric measurement (one channel for simplicity) was based on a voltage clamp circuit. Rf: …
Figure 2—figure supplement 1
Amperometric currents reliably track LFP spectral content over a wide frequency range.
(A) Representative power spectrogram from high-frequency range of electrophysiology and amperometry derived LFP signals in the CA1 pyramidal layer during NREM sleep. Arrows indicate timings of SWRs …
Figure 2—figure supplement 2
Tonic COA dynamics across brain states in a freely moving animal.
(A) Representative recording across multiple brain states showing power spectrogram from a silicon probe site at hippocampal fissure (top), rat speed (middle) and clean ChOx signal (bottom). (B) …
Figure 3 with 2 supplements
Biosensors generate tonic and phasic COA components in response to O2.
(A) The voltammogram shows the DC voltage-related sensitivity of gold-plated sites toward H2O2 (n = 10) and O2 (n = 5). (B) An example of an in vitro O2 calibration. Upon removal of O2 from PBS …
Figure 3—figure supplement 1
Oxygen measurement with the TACO sensor does not affect the simultaneously recorded COA signal.
Example of a switch of the potential applied to the Au site in vivo from the normally used +0.6 V vs. Ag/AgCl in sentinel mode to −0.2 V vs. Ag/AgCl used for O2 measurement. No change was observed …
Figure 3—figure supplement 2
Phasic biosensor responses to O2in vitro.
Amplitude of phasic response (color) as a function of cumulative O2 after each addition, sorted by sensor’s tonic KmO2app. Amplitudes were calculated as Ch concentration, based on sensors’ response …
Figure 4 with 2 supplements
Mathematical model explains ChOx-based biosensor COA responses to oxygen.
(A) Simulated calibrations of biosensors with different enzyme concentrations in the coating (coating thickness of 30 μm). Choline in bulk solution was kept constant at 5 μM and O2 was incremented …
Figure 4—figure supplement 1
Mathematical simulation of ChOx-biosensor tonic responses and reduced enzyme-bound intermediate dynamics.
(A) Maximal cumulative tonic sensor responses as a function of coating thickness and enzyme concentration in the coating. (B) Left shows simulated concentration dynamics of total reduced …
Figure 4—figure supplement 2
Minimal kinetic mechanism of Choline Oxidase.
(E) Free enzyme, (ECh) enzyme-bound Ch, (Ered) enzyme with reduced FAD co-factor, (Eox) enzyme with oxidized FAD co-factor, (BA) betaine aldehyde, (GB) glycine betaine.
Figure 5
Locomotion-related correlated changes in COA and local oxygen concentration in head-fixed mice.
(A) The schematics of the tetrode configuration used to simultaneously measure COA (H2O2) and extracellular O2.in head-fixed mice. Values on each recording site indicate the applied DC voltage vs. …
Figure 6 with 1 supplement
Correlated COA and oxygen transients follow hippocampal SWRs.
(A) Average COA and O2 dynamics triggered on hippocampal SWRs (n = 1067, top) and average LFP spectrogram (bottom) from a recording session in the head-fixed setup. (B) Pseudo-color-coded Spearman …
Figure 6—figure supplement 1
Phasic COA and oxygen responses following SWRs jointly depend on their power and grouping.
Amplitude of ChOx activity and O2 transients as a function of SWR count in a 2 s time window, sorted by different percentile ranges of summed ripple power. The data was collected from three …
Figure 7 with 1 supplement
Correlation between COA and spontaneous O2 transients suggests O2-COA directionality.
(A) Average COA and O2 dynamics triggered to fast O2 transients (duration ~5 s) detected outside periods when SWRs or locomotion bouts occurred. Data is from one recording session (n = 42 events). (B…
Figure 7—figure supplement 1
COA dynamics associated with O2 transients across all experiments.
(A–B) plots display the same statistics as in an example on Figure 5E, but for all recordings (A) Lag of ChOx activity peaks relative to O2 for changes in O2 detected with varying rise time (from …
Figure 8 with 1 supplement
Exogeneous O2 elicits phasic COA responses in the hippocampus in vivo.
(A) Representative examples of slow and fast O2 transients and associated COA responses evoked by local application of exogenous O2 from a glass micropipette. (B) Amplitudes of COA vs. locally evoked…
Figure 8—figure supplement 1
Raw sensor responses evoked by exogenous oxygen in vivo.
(A) Normalized O2 and COA transients evoked by local O2 application, sorted by O2 rise time. Events were obtained from three recording sessions (n = 13–40 per session). (B) Normalized O2 and COA …
Tables
Table 1
Analytical properties of TACO sensors.
| Individual sites’ analytical properties | ||||||
|---|---|---|---|---|---|---|
| Channel type | Ch sensitivity (pA/µM) | Ch sensitivity (nA µM−1 cm−2) | H2O2 sensitivity (pA/µM) | DA sensitivity (pA/µM) | AA sensitivity (pA/µM) | Impedance (GΩ) |
| Au/Pt/m-PD | 2.45 ± 0.70 (n = 10) | 1081 ± 309 (n = 10) | 2.48 ± 0.93 (n = 8) | 0.15 ± 0.23(n = 10) | 0.02 ± 0.013(n = 10) | 2.90 ± 0.48 (n = 5) |
| Au/Pt | 2.54 ± 0.64 (n = 8) | 1118 ± 283 (n = 8) | 2.86 ± 1.10 (n = 6) | 7.48 ± 1.86(n = 8) | 0.22 ± 0.20(n = 8) | 3.38 ± 0.56 (n = 5) |
| Au/m-PD | 0.27 ± 0.12 (n = 10) | 118.2 ± 53 (n = 10) | 0.22 ± 0.16 (n = 8) | 0.13 ± 0.23 (n = 10) | 0.007 ± 0.004 (n = 10) | 3.11 ± 0.77 (n = 5) |
| Au | 0.25 ± 0.086 (n = 9) | 111.5 ± 38 (n = 10) | 0.29 ± 0.08 (n = 7) | 8.24 ± 1.84 (n = 9) | 0.19 ± 0.16 (n = 9) | 3.65 ± 0.59 (n = 5) |
| Analytical properties for COA measurement (Au/Pt/m-PD - Au/m-PD) | ||||||
|---|---|---|---|---|---|---|
| Ch sensitivity (pA/µM) | Limit of detection (nM) | Linearity, [Ch]<30 µM (R2) | Response time (s) | DA sensitivity (pA/µM), selectivity ratio | AA sensitivity (pA/µM), selectivity ratio | |
| 2.18 ± 0.73 (n = 10) | 28 ± 0.011 (n = 10) | 0.9996 ± 0.0003 (n = 10) | 1.4 ± 0.4 (n = 10) | 0.022 ± 0.38 (n = 10), 101:1 | 0.013 ± 0.012 (n = 10), 169:1 | |
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The data are given as the mean ± CI (95%).
The number of sensors tested is given in parentheses. Data were collected from calibrations on the day after m-PD electropolymerization.
Key resources table
| Reagent type (species) or resource | Designation | Source or reference | Identifiers | Additional information |
|---|---|---|---|---|
| Chemical compound, drug | Chitosan | Sigma-Aldrich | 448869 | |
| Chemical compound, drug | Chloroplatinic acid hydrate | Sigma-Aldrich | 520896 | |
| Chemical compound, drug | Choline chloride | Sigma-Aldrich | C7017 | |
| Chemical compound, drug | Choline oxidase from Alcaligenes sp. | Sigma-Aldrich | C5896 | |
| Chemical compound, drug | Dopamine hydrochloride | Sigma-Aldrich | H8502 | |
| Chemical compound, drug | Gold chloride solution | Sigma-Aldrich | HT1004 | |
| Chemical compound, drug | Hydrogen peroxide | Sigma-Aldrich | 216763 | |
| Chemical compound, drug | m-Phenylenediamine | Sigma-Aldrich | P23954 | |
| Chemical compound, drug | p-Benzoquinone | Sigma-Aldrich | B10358 | |
| Chemical compound, drug | Sodium-L-Ascorbate | Sigma-Aldrich | A7631 |
Table 2
Values of constants used in the biosensor model.
| Constant | Value | Reference |
|---|---|---|
| kf* | 2 × 106 M−1 s−1 | Fan and Gadda, 2005 |
| kr* | 580 s−1 | Fan and Gadda, 2005 |
| k1 | 93 s−1 | Fan and Gadda, 2005 |
| k2 | 8.64 × 104 M−1 s−1 | Fan and Gadda, 2005 |
| k3 | 135 s−1 | Fan and Gadda, 2005 |
| k4 | 5.34 × 104 M−1 s−1 | Fan and Gadda, 2005 |
| k5 | 200 s−1 | Fan and Gadda, 2005 |
| DCh† | 1197 μm2 s−1 | Valencia and González, 2012 |
| DO2‡ | 2500 μm2 s−1 | Santos et al., 2011 |
| DH2O2 | 1830 μm2 s−1 | van Stroe-Biezen et al., 1993 |
| α | 0.8 |
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* Estimated based on Kd, Kcat and Km values of ChOx for choline.
†Estimated using the Stokes−Einstein Gierer-Wirtz Estimation method.
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‡Extrapolated from room temperature to 37°C using a factor of 2.6% per degree (Han and Bartels, 1996).
