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Measurement of Local Partial Pressure of Oxygen in the Brain Tissue under Normoxia and Epilepsy with Phosphorescence Lifetime Microscopy.

Zhang C, Bélanger S, Pouliot P, Lesage F - PLoS ONE (2015)

Bottom Line: In this work a method for measuring brain oxygen partial pressure with confocal phosphorescence lifetime microscopy system is reported.When used in conjunction with a dendritic phosphorescent probe, Oxyphor G4, this system enabled minimally invasive measurements of oxygen partial pressure (pO2) in cerebral tissue with high spatial and temporal resolution during 4-AP induced epileptic seizures.Our results reveal a correlation between the percent change in the pO2 signal during the "initial dip" and the duration of seizure-like activity, which can help localize the epileptic focus and predict the length of seizure.

View Article: PubMed Central - PubMed

Affiliation: École Polytechnique de Montréal, Department of Electrical Engineering, C.P. 6079 succ.Centre-ville, Montreal, Quebec, Canada, H3C 3A7.

ABSTRACT
In this work a method for measuring brain oxygen partial pressure with confocal phosphorescence lifetime microscopy system is reported. When used in conjunction with a dendritic phosphorescent probe, Oxyphor G4, this system enabled minimally invasive measurements of oxygen partial pressure (pO2) in cerebral tissue with high spatial and temporal resolution during 4-AP induced epileptic seizures. Investigating epileptic events, we characterized the spatio-temporal distribution of the "initial dip" in pO2 near the probe injection site and along nearby arterioles. Our results reveal a correlation between the percent change in the pO2 signal during the "initial dip" and the duration of seizure-like activity, which can help localize the epileptic focus and predict the length of seizure.

No MeSH data available.


Related in: MedlinePlus

Temperature dependencies of oxygen quenching constants (Kq) and lifetimes (τ0) for G4 (a and b).The measurements were performed using 50 μM solutions of the probes, pH 7.23.
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pone.0135536.g001: Temperature dependencies of oxygen quenching constants (Kq) and lifetimes (τ0) for G4 (a and b).The measurements were performed using 50 μM solutions of the probes, pH 7.23.

Mentions: Phosphorescence lifetime microscopy has been used previously to measure pO2 changes through phosphorescence of exogenous probes. Early phosphorescent probes, based on Pd porphyrins [13,28], required pre-binding to a macromolecular carrier (e.g. albumin) in order to enhance their aqueous solubility and bring their quenching parameters into the range compatible with physiological oxygen concentration [13,29]. Moreover, the albumin was a potential source of toxicity. Recently, Esipova et al. [30] developed a new probe, Oxyphor G4, which is free of these limitations. Oxyphor G4 is derived from Pd-meso-tetra-(3, 5-dicarboxyphenyl)-tetrabenzoporphyrin (PdTBP) and belongs to the group of dendritic oxygen probe [31]. It is highly soluble in aqueous environments and does not permeate biological membranes. It can operate in either albumin-rich (blood plasma) or albumin-free (interstitial space) environments at all physiological oxygen concentrations, from normoxic to deep hypoxic conditions. Oxyphor G4 used in these studies was obtained from Oxygen Enterprises Ltd (University of Pennsylvania, Philadelphia, PA 19104–6059, USA). Received Oxyphor G4 was calibrated before the experiments, first equilibrated with room air (21% O2) and then with a completely deoxygenated solution at various temperatures (results of calibration are shown in Fig 1). In vivo the measured parameters (Kq and τ0) were selected at temperature ~37°C. The phosphorescence lifetimes of Oxyphor G4 range from ~23 to ~215 μs in the physiological pO2 range (160 mmHg-0 mmHg).


Measurement of Local Partial Pressure of Oxygen in the Brain Tissue under Normoxia and Epilepsy with Phosphorescence Lifetime Microscopy.

Zhang C, Bélanger S, Pouliot P, Lesage F - PLoS ONE (2015)

Temperature dependencies of oxygen quenching constants (Kq) and lifetimes (τ0) for G4 (a and b).The measurements were performed using 50 μM solutions of the probes, pH 7.23.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4549327&req=5

pone.0135536.g001: Temperature dependencies of oxygen quenching constants (Kq) and lifetimes (τ0) for G4 (a and b).The measurements were performed using 50 μM solutions of the probes, pH 7.23.
Mentions: Phosphorescence lifetime microscopy has been used previously to measure pO2 changes through phosphorescence of exogenous probes. Early phosphorescent probes, based on Pd porphyrins [13,28], required pre-binding to a macromolecular carrier (e.g. albumin) in order to enhance their aqueous solubility and bring their quenching parameters into the range compatible with physiological oxygen concentration [13,29]. Moreover, the albumin was a potential source of toxicity. Recently, Esipova et al. [30] developed a new probe, Oxyphor G4, which is free of these limitations. Oxyphor G4 is derived from Pd-meso-tetra-(3, 5-dicarboxyphenyl)-tetrabenzoporphyrin (PdTBP) and belongs to the group of dendritic oxygen probe [31]. It is highly soluble in aqueous environments and does not permeate biological membranes. It can operate in either albumin-rich (blood plasma) or albumin-free (interstitial space) environments at all physiological oxygen concentrations, from normoxic to deep hypoxic conditions. Oxyphor G4 used in these studies was obtained from Oxygen Enterprises Ltd (University of Pennsylvania, Philadelphia, PA 19104–6059, USA). Received Oxyphor G4 was calibrated before the experiments, first equilibrated with room air (21% O2) and then with a completely deoxygenated solution at various temperatures (results of calibration are shown in Fig 1). In vivo the measured parameters (Kq and τ0) were selected at temperature ~37°C. The phosphorescence lifetimes of Oxyphor G4 range from ~23 to ~215 μs in the physiological pO2 range (160 mmHg-0 mmHg).

Bottom Line: In this work a method for measuring brain oxygen partial pressure with confocal phosphorescence lifetime microscopy system is reported.When used in conjunction with a dendritic phosphorescent probe, Oxyphor G4, this system enabled minimally invasive measurements of oxygen partial pressure (pO2) in cerebral tissue with high spatial and temporal resolution during 4-AP induced epileptic seizures.Our results reveal a correlation between the percent change in the pO2 signal during the "initial dip" and the duration of seizure-like activity, which can help localize the epileptic focus and predict the length of seizure.

View Article: PubMed Central - PubMed

Affiliation: École Polytechnique de Montréal, Department of Electrical Engineering, C.P. 6079 succ.Centre-ville, Montreal, Quebec, Canada, H3C 3A7.

ABSTRACT
In this work a method for measuring brain oxygen partial pressure with confocal phosphorescence lifetime microscopy system is reported. When used in conjunction with a dendritic phosphorescent probe, Oxyphor G4, this system enabled minimally invasive measurements of oxygen partial pressure (pO2) in cerebral tissue with high spatial and temporal resolution during 4-AP induced epileptic seizures. Investigating epileptic events, we characterized the spatio-temporal distribution of the "initial dip" in pO2 near the probe injection site and along nearby arterioles. Our results reveal a correlation between the percent change in the pO2 signal during the "initial dip" and the duration of seizure-like activity, which can help localize the epileptic focus and predict the length of seizure.

No MeSH data available.


Related in: MedlinePlus