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Huynh GT, Tunny SS, Frith JE, Meagher L, Corrie SR. Organosilica Nanosensors for Monitoring Spatiotemporal Changes in Oxygen Levels in Bacterial Cultures. ACS Sens 2024; 9:2383-2394. [PMID: 38687178 DOI: 10.1021/acssensors.3c02747] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2024]
Abstract
Oxygen plays a central role in aerobic metabolism, and while many approaches have been developed to measure oxygen concentration in biological environments over time, monitoring spatiotemporal changes in dissolved oxygen levels remains challenging. To address this, we developed a ratiometric core-shell organosilica nanosensor for continuous, real-time optical monitoring of oxygen levels in biological environments. The nanosensors demonstrate good steady state characteristics (KpSV = 0.40 L/mg, R2 = 0.95) and respond reversibly to changes in oxygen concentration in buffered solutions and report similar oxygen level changes in response to bacterial cell growth (Escherichia coli) in comparison to a commercial bulk optode-based sensing film. We further demonstrated that the oxygen nanosensors could be distributed within a growing culture of E. coli and used to record oxygen levels over time and in different locations within a static culture, opening the possibility of spatiotemporal monitoring in complex biological systems.
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Affiliation(s)
- Gabriel T Huynh
- Department of Chemical and Biological Engineering, Monash University, Clayton, VIC 3800, Australia
- Commonwealth Scientific and Industrial Research Organization (CSIRO) Manufacturing, Clayton, VIC 3168, Australia
| | - Salma S Tunny
- Department of Chemical and Biological Engineering, Monash University, Clayton, VIC 3800, Australia
| | - Jessica E Frith
- Department of Materials Science and Engineering, Monash University, Clayton, VIC 3800, Australia
- Australian Regenerative Medicine Institute, Monash University, Clayton, VIC 3800, Australia
- ARC Training Centre for Cell and Tissue Engineering Technologies, Monash University, Clayton, VIC 3800, Australia
| | - Laurence Meagher
- Department of Materials Science and Engineering, Monash University, Clayton, VIC 3800, Australia
- Australian Regenerative Medicine Institute, Monash University, Clayton, VIC 3800, Australia
- ARC Training Centre for Cell and Tissue Engineering Technologies, Monash University, Clayton, VIC 3800, Australia
| | - Simon R Corrie
- Department of Chemical and Biological Engineering, Monash University, Clayton, VIC 3800, Australia
- ARC Training Centre for Cell and Tissue Engineering Technologies, Monash University, Clayton, VIC 3800, Australia
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Golub AS, Song BK, Nugent WH, Pittman RN. Dynamics of PO 2 and VO 2 in resting and contracting rat spinotrapezius muscle. Front Physiol 2023; 14:1172834. [PMID: 37538372 PMCID: PMC10396398 DOI: 10.3389/fphys.2023.1172834] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Accepted: 07/03/2023] [Indexed: 08/05/2023] Open
Abstract
This study examined changes in interstitial PO2, which allowed calculation of VO2 during periods of rest, muscle contraction and recovery using an in situ rat spinotrapezius muscle preparation. The PO2 was measured using phosphorescence quenching microscopy and the muscle VO2 was calculated as the rate of O2 disappearance during brief periods of muscle compression to stop blood flow with a supra-systolic pressure. The PO2 and VO2 measurements were made during "5 s compression and 15 s recovery" (CR) cycles. With all three stimulation frequencies, 1, 2 and 4 Hz, the fall in interstitial PO2 and rise in VO2 from resting values occurred within the first 20 s of contraction. The PO2 during contraction became lower as stimulation frequency increased from 1 to 4 Hz. VO2 was higher at 2 Hz than at 1 Hz contraction. With cessation of stimulation, PO2 began increasing exponentially towards baseline values. After 1 and 2 Hz contraction, the fall in muscle VO2 was delayed by one CR cycle and then exponentially decreased towards resting values. After 4 Hz stimulation, VO2 increased for 2 cycles and then decreased. The post-contraction transients of PO2 and VO2 were not synchronous and had different time constants. With further analysis two distinct functional responses were identified across all stimulation frequencies having PO2 during contraction above or below 30 mmHg. The corresponding VO2 responses were different - for "high" PO2, muscle VO2 reached high levels, while for the "low" PO2 data set muscle VO2 remained low. Recovery patterns were similar to those described above. In summary, local microscopic PO2 and VO2 were measured in resting and contracting muscle in situ and the post-contraction transients of PO2 and VO2 were all much slower than the onset transients.
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Affiliation(s)
- Aleksander S. Golub
- Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA, United States
- Song Biotechnologies LLC, Cockeysville, MD, United States
| | - Bjorn K. Song
- Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA, United States
- Song Biotechnologies LLC, Cockeysville, MD, United States
| | - William H. Nugent
- Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA, United States
- Song Biotechnologies LLC, Cockeysville, MD, United States
| | - Roland N. Pittman
- Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA, United States
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Afas KC, Goldman D. A two-layer continuously distributed capillary O 2 transport model applied to blood flow regulation in resting skeletal muscle. J Theor Biol 2022; 539:111058. [PMID: 35181287 DOI: 10.1016/j.jtbi.2022.111058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 02/07/2022] [Accepted: 02/08/2022] [Indexed: 10/19/2022]
Abstract
The microcirculation is the site of direct oxygen transfer from blood to tissue, and also of oxygen delivery control via regulation of local blood flow. In addition, a number of diseases including type II diabetes mellitus (DMII) and sepsis are known to produce microcirculatory dysfunction in their early phases. Given the complexity of microvascular structure and physiology, and the difficulty of measuring tissue oxygenation at the micro-scale, mathematical modelling has been necessary for understanding the physiology and pathophysiology of O2 transport in the microcirculation and for interpreting in vivo experiments. To advance this area, a model of blood-tissue O2 transport in skeletal muscle was recently developed which uses continuously distributed capillaries and includes O2 diffusion, convection, and consumption. The present work extends this model to two adjacent layers of skeletal muscle with different blood flow rates and applies it to study steady-state O2 transport when flow regulation is stimulated using an O2 exchange chamber. To generate a model which may be validated through in vivo experiments, an overlying O2 permeable membrane is included. The model is solved using traditional methods including separation of variables and Fourier decomposition, and to ensure smooth profiles at the muscle-muscle and muscle-membrane interfaces matching conditions are developed. The study presents qualitative verification for the model, using visualizations of tissue PO2 distributions for varying capillary density (CD), and presents capillary velocity response values in the near layer for varying chamber PO2 under the assumption that outlet capillary O2 saturation is equalized between adjacent layers. These compensatory velocity profiles, along with effective 'no-flux' chamber PO2 values, are presented for varying CD and tissue O2 consumption values. Insights gained from the two-layer model provide guidance for interpreting and planning future in-vivo experiments, and also provide motivation for further development of the model to improve understanding of the interaction between O2 transport and blood flow regulation.
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Affiliation(s)
- Keith Christian Afas
- School of Biomedical Engineering, University of Western Ontario, London, N6G1G8, Ontario, CA
| | - Daniel Goldman
- School of Biomedical Engineering, University of Western Ontario, London, N6G1G8, Ontario, CA; Department of Medical Biophysics, University of Western Ontario, London, N6A5C1, Ontario, CA; Department of Applied Mathematics, University of Western Ontario, London, N6A5C1, Ontario, CA.
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Harms FA, Mik EG. In Vivo Assessment of Mitochondrial Oxygen Consumption. Methods Mol Biol 2021; 2277:175-185. [PMID: 34080152 DOI: 10.1007/978-1-0716-1270-5_12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/27/2024]
Abstract
The Protoporphyrin IX-Triplet State Lifetime Technique (PpIX-TSLT) has been proposed by us as a potential clinical noninvasive tool for monitoring mitochondrial function. We have been working on the development of mitochondrial respirometry for monitoring mitochondrial oxygen tension (mitoPO2) and mitochondrial oxygen consumption (mitoVO2) in skin. In this work, we describe the principles of the method in small experimental animals.
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Affiliation(s)
- Floor A Harms
- Department of Anesthesiology, Laboratory of Experimental Anesthesiology, Erasmus MC - University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Egbert G Mik
- Department of Anesthesiology, Laboratory of Experimental Anesthesiology, Erasmus MC - University Medical Center Rotterdam, Rotterdam, The Netherlands.
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Golub AS, Nugent WH, Song BK. Spike of interstitial PO 2 produced by a twitch in rhythmically contracted muscle. Physiol Rep 2021; 9:e14699. [PMID: 33400848 PMCID: PMC7785101 DOI: 10.14814/phy2.14699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 11/27/2020] [Accepted: 12/05/2020] [Indexed: 11/29/2022] Open
Abstract
Oxygen (O2 ) exchange between capillaries and muscle cells in exercising muscles is of great interest for physiology and kinesiology. However, methodical limitations prevent O2 measurements on the millisecond scale. To bypass the constraints of quasi-continuous recording, progressive measurements of O2 partial pressure (PO2 ) in rhythmically contracting skeletal muscle were compiled to describe the O2 kinetics surrounding and including a single muscle contraction. Phosphorescence quenching microscopy measured PO2 in the interstitium of the rat spinotrapezius muscle. Measurements were triggered by contraction-inducing electrical pulses. For the first 60 seconds, measurement preceeded stimulation. After 60, measurement followed with a progressive 20 ms increment. Thus, the first 60 measurements describe the overall PO2 response to electrical stimulation initiated after a 10 second rest period, while 61-100 (stroboscopic mode) were compiled into a single 800 ms profile of the PO2 transient surrounding muscle contraction. Thirty seconds of stimulated contractions decreased interstitial PO2 from a baseline of 71 ± 1.4 mmHg to an "active" steady-state of 43 ± 1.5 mmHg. The stroboscopic mode compilation revealed an unexpected post-contractile rise in PO2 as a 205 ms spike with a maximum amplitude of 58 ± 3.8 mmHg at 68 ms, which restored 58% of the PO2 drop from baseline. Interpretation of this phenomenon is based on classical experiments by G.V. Anrep (1935), who discovered the rapid thrust of blood flow associated with muscle contraction. In addition to the metabolic implications during exercise, the physiological impact of these PO2 spikes may grow with an increased rate of rhythmical contractions in muscle or heart. NEW&NOTEWORTHY: The principal finding is a spike of interstitial PO2 , produced by a twitch in a rhythmically contracting muscle. A possible mechanism is flushing capillaries with arterial blood by mechanical forces. A technical novelty is the PO2 measurement with a "stroboscopic mode" and progressively increasing delay between stimulator pulse and PO2 measuring. That permitted a 20 ms time resolution for a 205 ms spike duration, using an excitation flash rate one per second.
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Baumbach P, Schmidt-Winter C, Hoefer J, Derlien S, Best N, Herbsleb M, Coldewey SM. A Pilot Study on the Association of Mitochondrial Oxygen Metabolism and Gas Exchange During Cardiopulmonary Exercise Testing: Is There a Mitochondrial Threshold? Front Med (Lausanne) 2020; 7:585462. [PMID: 33409287 PMCID: PMC7779397 DOI: 10.3389/fmed.2020.585462] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Accepted: 10/15/2020] [Indexed: 12/28/2022] Open
Abstract
Background: Mitochondria are the key players in aerobic energy generation via oxidative phosphorylation. Consequently, mitochondrial function has implications on physical performance in health and disease ranging from high performance sports to critical illness. The protoporphyrin IX-triplet state lifetime technique (PpIX-TSLT) allows in vivo measurements of mitochondrial oxygen tension (mitoPO2). Hitherto, few data exist on the relation of mitochondrial oxygen metabolism and ergospirometry-derived variables during physical performance. This study investigates the association of mitochondrial oxygen metabolism with gas exchange and blood gas analysis variables assessed during cardiopulmonary exercise testing (CPET) in aerobic and anaerobic metabolic phases. Methods: Seventeen volunteers underwent an exhaustive CPET (graded multistage protocol, 50 W/5 min increase), of which 14 were included in the analysis. At baseline and for every load level PpIX-TSLT-derived mitoPO2 measurements were performed every 10 s with 1 intermediate dynamic measurement to obtain mitochondrial oxygen consumption and delivery (mito V . O2, mito D . O2). In addition, variables of gas exchange and capillary blood gas analyses were obtained to determine ventilatory and lactate thresholds (VT, LT). Metabolic phases were defined in relation to VT1 and VT2 (aerobic: <VT1, aerobic-anaerobic transition: ≥VT1 and <VT2 and anaerobic: ≥VT2). We used linear mixed models to compare variables of PpIX-TSLT between metabolic phases and to analyze their associations with variables of gas exchange and capillary blood gas analyses. Results: MitoPO2 increased from the aerobic to the aerobic-anaerobic phase followed by a subsequent decline. A mitoPO2 peak, termed mitochondrial threshold (MT), was observed in most subjects close to LT2. Mito D . O2 increased during CPET, while no changes in mito V . O2 were observed. MitoPO2 was negatively associated with partial pressure of end-tidal oxygen and capillary partial pressure of oxygen and positively associated with partial pressure of end-tidal carbon dioxide and capillary partial pressure of carbon dioxide. Mito D . O2 was associated with cardiovascular variables. We found no consistent association for mito V . O2. Conclusion: Our results indicate an association between pulmonary respiration and cutaneous mitoPO2 during physical exercise. The observed mitochondrial threshold, coinciding with the metabolic transition from an aerobic to an anaerobic state, might be of importance in critical care as well as in sports medicine.
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Affiliation(s)
- Philipp Baumbach
- Department of Anesthesiology and Intensive Care Medicine, Jena University Hospital, Jena, Germany.,Septomics Research Center, Jena University Hospital, Jena, Germany
| | - Christiane Schmidt-Winter
- Department of Anesthesiology and Intensive Care Medicine, Jena University Hospital, Jena, Germany.,Septomics Research Center, Jena University Hospital, Jena, Germany
| | - Jan Hoefer
- Department of Anesthesiology and Intensive Care Medicine, Jena University Hospital, Jena, Germany.,Septomics Research Center, Jena University Hospital, Jena, Germany
| | - Steffen Derlien
- Institute of Physiotherapy, Jena University Hospital, Jena, Germany
| | - Norman Best
- Institute of Physiotherapy, Jena University Hospital, Jena, Germany
| | - Marco Herbsleb
- Department of Sports Medicine and Health Promotion, Friedrich Schiller University, Jena, Germany
| | - Sina M Coldewey
- Department of Anesthesiology and Intensive Care Medicine, Jena University Hospital, Jena, Germany.,Septomics Research Center, Jena University Hospital, Jena, Germany.,Center for Sepsis Control and Care, Jena University Hospital, Jena, Germany
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Song BK, Light WR, Vandegriff KD, Tucker J, Nugent WH. Systemic and microvascular comparison of Lactated Ringer's solution, VIR-HBOC, and alpha-alpha crosslinked haemoglobin-based oxygen carrier in a rat 10% topload model. ARTIFICIAL CELLS NANOMEDICINE AND BIOTECHNOLOGY 2020; 48:1079-1088. [PMID: 32820690 DOI: 10.1080/21691401.2020.1809441] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Medical support for traumatic haemorrhage is lacking for far-forward combat units. VIR-HBOC (haemoglobin-based oxygen carrier) is a novel biological therapeutic under development as a field-stable resuscitation fluid. HBOCs have a long history of complications, chief among them is vasoconstrictive hypertension, which must be resolved before efficacy testing. As such, VIR-HBOC was compared against Lactated Ringers (LRS; vehicle) and a cross-linked haemoglobin (ααHb; a known vasoactive HBOC) in a rat topload model. Twenty-three male, Sprague Dawley rats were randomly assigned to receive a 10% infusion (estimated total blood volume) of one test article while normotensive and under anaesthesia. Cardiovascular, blood chemistry and oximetry, microvascular arteriolar diameters, and interstitial tissue oxygenation parameters were measured. Circulatory half-life was calculated by plasma total haemoglobin. Treatment with ααHb caused immediate increases in mean arterial pressure compared to LRS and VIR-HBOC groups, and corresponding arteriolar vasoconstriction (p < .05), which did not occur for LRS or VIR-HBOC. Circulatory half-lives for VIR-HBOC and ααHb were calculated as 340 and 157 min, respectively. This first report of VIR-HBOC showed no evidence of a hypertensive or vasoactive effect. It was well-tolerated over the eight-hour time course of this topload model, which warrants further investigation in studies of haemorrhagic shock.
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Hirai DM, Colburn TD, Craig JC, Hotta K, Kano Y, Musch TI, Poole DC. Skeletal muscle interstitial O 2 pressures: bridging the gap between the capillary and myocyte. Microcirculation 2018; 26:e12497. [PMID: 30120845 DOI: 10.1111/micc.12497] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Revised: 07/26/2018] [Accepted: 08/13/2018] [Indexed: 01/18/2023]
Abstract
The oxygen transport pathway from air to mitochondria involves a series of transfer steps within closely integrated systems (pulmonary, cardiovascular, and tissue metabolic). Small and finite O2 stores in most mammalian species require exquisitely controlled changes in O2 flux rates to support elevated ATP turnover. This is especially true for the contracting skeletal muscle where O2 requirements may increase two orders of magnitude above rest. This brief review focuses on the mechanistic bases for increased microvascular blood-myocyte O2 flux (V̇O2 ) from rest to contractions. Fick's law dictates that V̇O2 elevations driven by muscle contractions are produced by commensurate changes in driving force (ie, O2 pressure gradients; ΔPO2 ) and/or effective diffusing capacity (DO2 ). While previous evidence indicates that increased DO2 helps modulate contracting muscle O2 flux, up until recently the role of the dynamic ΔPO2 across the capillary wall was unknown. Recent phosphorescence quenching investigations of both microvascular and novel interstitial PO2 kinetics in health have resolved an important step in the O2 cascade between the capillary and myocyte. Specifically, the significant transmural ΔPO2 at rest was sustained (but not increased) during submaximal contractions. This supports the contention that the blood-myocyte interface provides a substantial effective resistance to O2 diffusion and underscores that modulations in erythrocyte hemodynamics and distribution (DO2 ) are crucial to preserve the driving force for O2 flux across the capillary wall (ΔPO2 ) during contractions. Investigation of the O2 transport pathway close to muscle mitochondria is key to identifying disease mechanisms and develop therapeutic approaches to ameliorate dysfunction and exercise intolerance.
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Affiliation(s)
- Daniel M Hirai
- Departments of Anatomy & Physiology, Kinesiology, Kansas State University, Manhattan, Kansas
| | - Trenton D Colburn
- Departments of Anatomy & Physiology, Kinesiology, Kansas State University, Manhattan, Kansas
| | - Jesse C Craig
- Departments of Anatomy & Physiology, Kinesiology, Kansas State University, Manhattan, Kansas
| | - Kazuki Hotta
- Department of Engineering Science, University of Electro-Communications, Tokyo, Japan
| | - Yutaka Kano
- Department of Engineering Science, University of Electro-Communications, Tokyo, Japan
| | - Timothy I Musch
- Departments of Anatomy & Physiology, Kinesiology, Kansas State University, Manhattan, Kansas
| | - David C Poole
- Departments of Anatomy & Physiology, Kinesiology, Kansas State University, Manhattan, Kansas
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Golub AS, Dodhy SC, Pittman RN. Oxygen dependence of respiration in rat spinotrapezius muscle contracting at 0.5-8 twitches per second. J Appl Physiol (1985) 2018; 125:124-133. [PMID: 29494286 DOI: 10.1152/japplphysiol.01136.2016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The oxygen dependence of respiration was obtained in situ in microscopic regions of rat spinotrapezius muscle for different levels of metabolic activity produced by electrical stimulation at rates from 0.5 to 8 Hz. The rate of O2 consumption (V̇o2) was measured with phosphorescence quenching microscopy (PQM) as the rate of O2 disappearance in a muscle with rapid flow arrest. The phosphorescent oxygen probe was loaded into the interstitial space of the muscle to give O2 tension (Po2) in the interstitium. A set of sigmoid curves relating the Po2 dependence of V̇o2 was obtained with a Po2-dependent region below a characteristic Po2 (~30 mmHg) and a Po2-independent region above this Po2. The V̇o2(Po2) plots were fit by the Hill equation containing O2 demand (rest to 8 Hz: 216 ± 26 to 636 ± 77 nl O2/cm3 s) and the Po2 value corresponding to O2 demand/2 (rest to 8 Hz: 22 ± 4 to 11 ± 1 mmHg). The initial Po2 and V̇o2 pairs of values measured at the moment of flow arrest formed a straight line, determining the rate of oxygen supply. This line had a negative slope, equal to the oxygen conductance for the O2 supply chain. For each level of tissue blood flow the set of possible values of Po2 and V̇o2 consists of the intersection points between this O2 supply line and the set of V̇o2 curves. An electrical analogy for the intraorgan O2 supply and consumption is an inverting transistor amplifier, which allows the use of graphic analysis methods for prediction of the behavior of the oxygen processing system in organs. NEW & NOTEWORTHY The sigmoidal shape of curves describing oxygen dependence of muscle respiration varies from basal to maximal workload and characterizes the oxidative metabolism of muscle. The rate of O2 supply depends on extracellular O2 tension and is determined by the overall oxygen conductance in the muscle. The dynamics of oxygen consumption is determined by the supply line that intersects the oxygen demand curves. An electrical analogy for the oxygen supply/consumption system is an inverting transistor amplifier.
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Affiliation(s)
- Aleksander S Golub
- Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University , Richmond, Virginia
| | - Sami C Dodhy
- Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University , Richmond, Virginia
| | - Roland N Pittman
- Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University , Richmond, Virginia
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Harms F, Stolker RJ, Mik E. Cutaneous Respirometry as Novel Technique to Monitor Mitochondrial Function: A Feasibility Study in Healthy Volunteers. PLoS One 2016; 11:e0159544. [PMID: 27455073 PMCID: PMC4959702 DOI: 10.1371/journal.pone.0159544] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Accepted: 07/04/2016] [Indexed: 01/16/2023] Open
Abstract
Background The protoporphyrin IX-triplet state lifetime technique (PpIX-TSLT) is proposed as a potential clinical non-invasive tool to monitor mitochondrial function. This technique has been evaluated in several animal studies. Mitochondrial respirometry allows measurement in vivo of mitochondrial oxygen tension (mitoPO2) and mitochondrial oxygen consumption (mitoVO2) in skin. This study describes the first use of a clinical prototype in skin of humans. Methods The clinical prototype was tested in 30 healthy volunteers. A self-adhesive patch containing 2 mg 5-aminolevulinic acid (ALA) was applied on the skin of the anterior chest wall (sternal) for induction of mitochondrial protoporphyrin IX and was protected from light for 5 h. MitoPO2 was measured by means of oxygen-dependent delayed fluorescence of protoporphyrin IX. MitoVO2 was determined by dynamic mitoPO2 measurements on the primed skin, while locally blocking oxygen supply by applying local pressure with the measurement probe. MitoPO2 was recorded before and during a 60-s period of compression of the microcirculation, at an interval of 1 Hz. Oxygen consumption (i.e. the local oxygen disappearance rate) was calculated from the decay of the mitoPO2 slope. Results Oxygen-dependent delayed fluorescence measurements were successfully performed in the skin of 27 volunteers. The average value (± SD) of mitoPO2 was 44 ± 17 mmHg and mean mitoVO2 values were 5.8 ± 2.3 and 6.1 ± 1.6 mmHg s-1 at a skin temperature of 34°C and 40°C, respectively. No major discomfort during measurement and no long-term dermatological abnormalities were reported in a survey performed 1 month after measurements. Conclusion These results show that the clinical prototype allows measurement of mitochondrial oxygenation and oxygen consumption in humans. The development of this clinically applicable device offers opportunities for further evaluation of the technique in humans and the start of first clinical studies.
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Affiliation(s)
- Floor Harms
- Department of Anesthesiology, Laboratory of Experimental Anesthesiology, Erasmus University Medical Center Rotterdam, ‘s-Gravendijkwal 230, 3015 CE Rotterdam, The Netherlands
- * E-mail:
| | - Robert Jan Stolker
- Department of Anesthesiology, Laboratory of Experimental Anesthesiology, Erasmus University Medical Center Rotterdam, ‘s-Gravendijkwal 230, 3015 CE Rotterdam, The Netherlands
| | - Egbert Mik
- Department of Anesthesiology, Laboratory of Experimental Anesthesiology, Erasmus University Medical Center Rotterdam, ‘s-Gravendijkwal 230, 3015 CE Rotterdam, The Netherlands
- Department of Intensive Care, Erasmus University Medical Center Rotterdam, ‘s-Gravendijkwal 230, 3015 CE Rotterdam, The Netherlands
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Golub AS, Pittman RN. Barometric calibration of a luminescent oxygen probe. J Appl Physiol (1985) 2016; 120:809-16. [PMID: 26846556 DOI: 10.1152/japplphysiol.01007.2015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 01/28/2016] [Indexed: 01/09/2023] Open
Abstract
The invention of the phosphorescence quenching method for the measurement of oxygen concentration in blood and tissue revolutionized physiological studies of oxygen transport in living organisms. Since the pioneering publication by Vanderkooi and Wilson in 1987, many researchers have contributed to the measurement of oxygen in the microcirculation, to oxygen imaging in tissues and microvessels, and to the development of new extracellular and intracellular phosphorescent probes. However, there is a problem of congruency in data from different laboratories, because of interlaboratory variability of the calibration coefficients in the Stern-Volmer equation. Published calibrations for a common oxygen probe, Pd-porphyrin + bovine serum albumin (BSA), vary because of differences in the techniques used. These methods are used for the formation of oxygen standards: chemical titration, calibrated gas mixtures, and an oxygen electrode. Each method in turn also needs calibration. We have designed a barometric method for the calibration of oxygen probes by using a regulated vacuum to set multiple PO2 standards. The method is fast and accurate and can be applied to biological fluids obtained during or after an experiment. Calibration over the full physiological PO2 range (1-120 mmHg) takes ∼15 min and requires 1-2 mg of probe.
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Affiliation(s)
- Aleksander S Golub
- Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
| | - Roland N Pittman
- Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
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12
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Nugent WH, Song BK, Pittman RN, Golub AS. Simultaneous sampling of tissue oxygenation and oxygen consumption in skeletal muscle. Microvasc Res 2015; 105:15-22. [PMID: 26683232 DOI: 10.1016/j.mvr.2015.12.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Revised: 12/08/2015] [Accepted: 12/08/2015] [Indexed: 01/07/2023]
Abstract
Under physiologic conditions, microvascular oxygen delivery appears to be well matched to oxygen consumption in respiring tissues. We present a technique to measure interstitial oxygen tension (PISFO2) and oxygen consumption (VO2) under steady-state conditions, as well as during the transitions from rest to activity and back. Phosphorescence Quenching Microscopy (PQM) was employed with pneumatic compression cycling to achieve 1 to 10 Hz sampling rates of interstitial PO2 and simultaneous recurrent sampling of VO2 (3/min) in the exteriorized rat spinotrapezius muscle. The compression pressure was optimized to 120-130 mmHg without adverse effect on the tissue preparation. A cycle of 5s compression followed by 15s recovery yielded a resting VO2 of 0.98 ± 0.03 ml O2/100 cm(3)min while preserving microvascular oxygen delivery. The measurement system was then used to assess VO2 dependence on PISFO2 at rest and further tested under conditions of isometric muscle contraction to demonstrate a robust ability to monitor the on-kinetics of tissue respiration and the compensatory changes in PISFO2 during contraction and recovery. The temporal and spatial resolution of this approach is well suited to studies seeking to characterize microvascular oxygen supply and demand in thin tissues.
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Affiliation(s)
- William H Nugent
- Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Bjorn K Song
- Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Roland N Pittman
- Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298, USA.
| | - Aleksander S Golub
- Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298, USA
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Abstract
The protoporphyrin IX-triplet state lifetime technique (PpIX-TSLT) has been proposed by us as a potential clinical noninvasive tool for monitoring mitochondrial function. We have been working on the development of mitochondrial respirometry for monitoring mitochondrial oxygen tension (mitoPO2) and mitochondrial oxygen consumption (mitoVO2) in skin. In this work we describe the principles of the method in experimental animals.
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Affiliation(s)
- Floor A Harms
- Department of Anesthesiology, Laboratory of Experimental Anesthesiology, Erasmus MC - University Medical Center Rotterdam, 's-Gravendijkwal 230, 3015 CE, Rotterdam, The Netherlands
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Harms FA, Bodmer SIA, Raat NJH, Mik EG. Cutaneous mitochondrial respirometry: non-invasive monitoring of mitochondrial function. J Clin Monit Comput 2014; 29:509-19. [PMID: 25388510 DOI: 10.1007/s10877-014-9628-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Accepted: 10/07/2014] [Indexed: 11/28/2022]
Abstract
The recently developed technique for measuring cutaneous mitochondrial oxygen tension (mitoPO2) by means of the Protoporphyrin IX-Triplet State Lifetime Technique (PpIX-TSLT) provides new opportunities for assessing mitochondrial function in vivo. The aims of this work were to study whether cutaneous mitochondrial measurements reflect mitochondrial status in other parts of the body and to demonstrate the feasibility of the technique for potential clinical use. The first part of this paper demonstrates a correlation between alterations in mitochondrial parameters in skin and other tissues during endotoxemia. Experiments were performed in rats in which mitochondrial dysfunction was induced by a lipopolysaccharide-induced sepsis (n = 5) and a time control group (n = 5). MitoPO2 and mitochondrial oxygen consumption (mitoVO2) were measured using PpIX-TSLT in skin, liver and buccal mucosa of the mouth. Both skin and buccal mucosa show a significant mitoPO2-independent decrease (P < 0.05) in mitoVO2 after LPS infusion (a decrease of 37 and 39% respectively). In liver both mitoPO2 and mitoVO2 decreased significantly (33 and 27% respectively). The second part of this paper describes the clinical concept of monitoring cutaneous mitochondrial respiration in man. A first prototype of a clinical PpIX-TSLT monitor is described and its usability is demonstrated on human skin. We expect that clinical implementation of this device will greatly contribute to our understanding of mitochondrial oxygenation and oxygen metabolism in perioperative medicine and in critical illness. Our ultimate goal is to develop a clinical monitor for mitochondrial function and the current results are an important step forward.
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Affiliation(s)
- Floor A Harms
- Department of Anesthesiology, Laboratory of Experimental Anesthesiology, Erasmus MC - University Medical Center Rotterdam, 's-Gravendijkwal 230, 3015 CE, Rotterdam, The Netherlands,
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Golub AS, Song BK, Pittman RN. Muscle contraction increases interstitial nitric oxide as predicted by a new model of local blood flow regulation. J Physiol 2014; 592:1225-35. [PMID: 24445318 DOI: 10.1113/jphysiol.2013.267302] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The prevailing metabolic theory of local blood flow regulation suggests the dilatation of arterioles in response to tissue hypoxia via the emission of multiple metabolic vasodilators by parenchymal cells. We have proposed a mechanism of regulation, built from well-known components, which assumes that arterioles are normally dilated in metabolically active tissues, due to the emission of NO by the endothelium of microvessels. Regulation of local blood flow aims at preventing an excessive supply of oxygen (O2) and glucose to the tissue and thus provides an adequate supply, in contrast to the metabolic regulation theory which requires permanent hypoxia to generate the metabolic vasodilators. The mediator of the restrictive signal is superoxide anion (O2(-)) released by membrane NAD(P)H oxidases into the interstitial space, where it neutralizes NO at a diffusion-limited rate. This model predicts that the onset of muscle contraction will lead to the cessation of O2(-) production, which will cause an elevation of interstitial NO concentration and an increase in fluorescence of the NO probe DAF-FM after its conversion to DAF-T. The time course of DAF-T fluorescence in contracting muscle is predicted by also considering the washout from the muscle of the interstitially loaded NO indicator. Experiments using pulse fluorimetry confirmed an increase in the interstitial concentration of NO available for reaction with DAF-FM during bouts of muscle contraction. The sharp increase in interstitial [NO] is consistent with the hypothesis that the termination of the neutralizing superoxide flow into the interstitium is associated with the activation of mitochondria and a reduction of the interstitial oxygen tension. The advantage of the new model is its ability to explain the interaction of metabolic activity and local blood flow through the adequate delivery of glucose and oxygen.
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Affiliation(s)
- Aleksander S Golub
- Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University, 1101 E. Marshall Street, PO Box 980551, Richmond, VA 23298-0551, USA.
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Effects of perfluorocarbon emulsions on microvascular blood flow and oxygen transport in a model of severe arterial gas embolism. J Surg Res 2014; 187:324-33. [DOI: 10.1016/j.jss.2013.08.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Revised: 07/18/2013] [Accepted: 08/12/2013] [Indexed: 11/19/2022]
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Cutaneous respirometry by dynamic measurement of mitochondrial oxygen tension for monitoring mitochondrial function in vivo. Mitochondrion 2013; 13:507-14. [DOI: 10.1016/j.mito.2012.10.005] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Revised: 09/19/2012] [Accepted: 10/02/2012] [Indexed: 11/23/2022]
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Pittman RN. Oxygen transport in the microcirculation and its regulation. Microcirculation 2013; 20:117-37. [PMID: 23025284 DOI: 10.1111/micc.12017] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Accepted: 09/27/2012] [Indexed: 11/27/2022]
Abstract
OBJECTIVE Cells require energy to carry out their functions and they typically use oxidative phosphorylation to generate the needed ATP. Thus, cells have a continuous need for oxygen, which they receive by diffusion from the blood through the interstitial fluid. The circulatory system pumps oxygen-rich blood through a network of increasingly minute vessels, the microcirculation. The structure of the microcirculation is such that all cells have at least one nearby capillary for diffusive exchange of oxygen and red blood cells release the oxygen bound to hemoglobin as they traverse capillaries. METHODS This review focuses first on the historical development of techniques to measure oxygen at various sites in the microcirculation, including the blood, interstitium, and cells. RESULTS Next, approaches are described as to how these techniques have been employed to make discoveries about different aspects of oxygen transport. Finally, ways in which oxygen might participate in the regulation of blood flow toward matching oxygen supply to oxygen demand is discussed. CONCLUSIONS Overall, the transport of oxygen to the cells of the body is one of the most critical functions of the cardiovascular system and it is in the microcirculation where the final local determinants of oxygen supply, oxygen demand, and their regulation are decided.
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Affiliation(s)
- Roland N Pittman
- Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia, USA.
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Yin B, Kuranov RV, McElroy AB, Kazmi S, Dunn AK, Duong TQ, Milner TE. Dual-wavelength photothermal optical coherence tomography for imaging microvasculature blood oxygen saturation. JOURNAL OF BIOMEDICAL OPTICS 2013; 18:56005. [PMID: 23640076 PMCID: PMC3642243 DOI: 10.1117/1.jbo.18.5.056005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
A swept-source dual-wavelength photothermal (DWP) optical coherence tomography (OCT) system is demonstrated for quantitative imaging of microvasculature oxygen saturation. DWP-OCT is capable of recording three-dimensional images of tissue and depth-resolved phase variation in response to photothermal excitation. A 1,064-nm OCT probe and 770-nm and 800-nm photothermal excitation beams are combined in a single-mode optical fiber to measure microvasculature hemoglobin oxygen saturation (SO(2)) levels in phantom blood vessels with a range of blood flow speeds (0 to 17 mm/s). A 50-μm-diameter blood vessel phantom is imaged, and SO(2) levels are measured using DWP-OCT and compared with values provided by a commercial oximeter at various blood oxygen concentrations. The influences of blood flow speed and mechanisms of SNR phase degradation on the accuracy of SO(2) measurement are identified and investigated.
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Affiliation(s)
- Biwei Yin
- University of Texas at Austin, Departments of Electrical and Computer Engineering, 1 University Station C0803, Austin, Texas 78712
| | - Roman V. Kuranov
- University of Texas Health Science Center at San Antonio, Department of Ophthalmology, 7703 Floyd Curl Drive, San Antonio, Texas 78229
- Address all correspondence to: Roman V. Kuranov, University of Texas Health Science Center at San Antonio, Department of Ophthalmology, 7703 Floyd Curl Drive, San Antonio, Texas 78229. Tel: 210-567-8402; Fax: 210-567-8413; E-mail:
| | - Austin B. McElroy
- University of Texas at Austin, Department of Biomedical Engineering, 1 University Station C0800, Austin, Texas 78712
| | - Shams Kazmi
- University of Texas at Austin, Department of Biomedical Engineering, 1 University Station C0800, Austin, Texas 78712
| | - Andrew K. Dunn
- University of Texas at Austin, Department of Biomedical Engineering, 1 University Station C0800, Austin, Texas 78712
| | - Timothy Q. Duong
- University of Texas Health Science Center at San Antonio, Department of Ophthalmology, 7703 Floyd Curl Drive, San Antonio, Texas 78229
| | - Thomas E. Milner
- University of Texas at Austin, Department of Biomedical Engineering, 1 University Station C0800, Austin, Texas 78712
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Golub AS, Pittman RN. Oxygen dependence of respiration in rat spinotrapezius muscle in situ. Am J Physiol Heart Circ Physiol 2012; 303:H47-56. [PMID: 22523254 DOI: 10.1152/ajpheart.00131.2012] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The oxygen dependence of respiration in striated muscle in situ was studied by measuring the rate of decrease of interstitial Po(2) [oxygen disappearance curve (ODC)] following rapid arrest of blood flow by pneumatic tissue compression, which ejected red blood cells from the muscle vessels and made the ODC independent from oxygen bound to hemoglobin. After the contribution of photo-consumption of oxygen by the method was evaluated and accounted for, the corrected ODCs were converted into the Po(2) dependence of oxygen consumption, Vo(2), proportional to the rate of Po(2) decrease. Fitting equations obtained from a model of heterogeneous intracellular Po(2) were applied to recover the parameters describing respiration in muscle fibers, with a predicted sigmoidal shape for the dependence of Vo(2) on Po(2). This curve consists of two regions connected by the point for critical Po(2) of the cell (i.e., Po(2) at the sarcolemma when the center of the cell becomes anoxic). The critical Po(2) was below the Po(2) for half-maximal respiratory rate (P(50)) for the cells. In six muscles at rest, the rate of oxygen consumption was 139 ± 6 nl O(2)/cm(3)·s and mitochondrial P(50) was k = 10.5 ± 0.8 mmHg. The range of Po(2) values inside the muscle fibers was found to be 4-5 mmHg at the critical Po(2). The oxygen dependence of respiration can be studied in thin muscles under different experimental conditions. In resting muscle, the critical Po(2) was substantially lower than the interstitial Po(2) of 53 ± 2 mmHg, a finding that indicates that Vo(2) under this circumstance is independent of oxygen supply and is discordant with the conventional hypothesis of metabolic regulation of the oxygen supply to tissue.
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Affiliation(s)
- Aleksander S Golub
- Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, 23298-0551, USA.
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Dmitriev RI, Zhdanov AV, Jasionek G, Papkovsky DB. Assessment of Cellular Oxygen Gradients with a Panel of Phosphorescent Oxygen-Sensitive Probes. Anal Chem 2012; 84:2930-8. [DOI: 10.1021/ac3000144] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Optical probes and techniques for O2 measurement in live cells and tissue. Cell Mol Life Sci 2012; 69:2025-39. [PMID: 22249195 PMCID: PMC3371327 DOI: 10.1007/s00018-011-0914-0] [Citation(s) in RCA: 138] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2011] [Revised: 12/19/2011] [Accepted: 12/29/2011] [Indexed: 01/03/2023]
Abstract
In recent years, significant progress has been achieved in the sensing and imaging of molecular oxygen (O2) in biological samples containing live cells and tissue. We review recent developments in the measurement of O2 in such samples by optical means, particularly using the phosphorescence quenching technique. The main types of soluble O2 sensors are assessed, including small molecule, supramolecular and particle-based structures used as extracellular or intracellular probes in conjunction with different detection modalities and measurement formats. For the different O2 sensing systems, particular attention is paid to their merits and limitations, analytical performance, general convenience and applicability in specific biological applications. The latter include measurement of O2 consumption rate, sample oxygenation, sensing of intracellular O2, metabolic assessment of cells, and O2 imaging of tissue, vasculature and individual cells. Altogether, this gives the potential user a comprehensive guide for the proper selection of the appropriate optical probe(s) and detection platform to suit their particular biological applications and measurement requirements.
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Kuranov RV, Kazmi S, McElroy AB, Kiel JW, Dunn AK, Milner TE, Duong TQ. In vivo depth-resolved oxygen saturation by Dual-Wavelength Photothermal (DWP) OCT. OPTICS EXPRESS 2011; 19:23831-44. [PMID: 22109408 PMCID: PMC3482904 DOI: 10.1364/oe.19.023831] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Microvasculature hemoglobin oxygen saturation (SaO2) is important in the progression of various pathologies. Non-invasive depth-resolved measurement of SaO2 levels in tissue microvasculature has the potential to provide early biomarkers and a better understanding of the pathophysiological processes allowing improved diagnostics and prediction of disease progression. We report proof-of-concept in vivo depth-resolved measurement of SaO(2) levels in selected 30 µm diameter arterioles in the murine brain using Dual-Wavelength Photothermal (DWP) Optical Coherence Tomography (OCT) with 800 nm and 770 nm photothermal excitation wavelengths. Depth location of back-reflected light from a target arteriole was confirmed using Doppler and speckle contrast OCT images. SaO(2) measured in a murine arteriole with DWP-OCT is linearly correlated (R(2)=0.98) with systemic SaO(2) values recorded by a pulse-oximeter. DWP-OCT are steadily lower (10.1%) than systemic SaO(2) values except during pure oxygen breathing. DWP-OCT is insensitive to OCT intensity variations and is a candidate approach for in vivo depth-resolved quantitative imaging of microvascular SaO(2) levels.
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Affiliation(s)
- Roman V Kuranov
- Department of Ophthalmology, The University of Texas Health Science Center, San Antonio, Texas 78229, USA.
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Esipova TV, Karagodov A, Miller J, Wilson DF, Busch TM, Vinogradov SA. Two new "protected" oxyphors for biological oximetry: properties and application in tumor imaging. Anal Chem 2011; 83:8756-65. [PMID: 21961699 DOI: 10.1021/ac2022234] [Citation(s) in RCA: 170] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
We report the synthesis, calibration, and examples of application of two new phosphorescent probes, Oxyphor R4 and Oxyphor G4, optimized specifically for in vivo oxygen imaging by phosphorescence quenching. These "protected" dendritic probes 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. Oxyphors R4 and G4 are derived from phosphorescent Pd-meso-tetra-(3,5-dicarboxyphenyl)-porphyrin (PdP) or Pd-meso-tetra-(3,5-dicarboxyphenyl)-tetrabenzoporphyrin (PdTBP), respectively, and possess features common for protected dendritic probes, i.e., hydrophobic dendritic encapsulation of phosphorescent metalloporphyrins and hydrophilic PEGylated periphery. The new Oxyphors are highly soluble in aqueous environments and do not permeate biological membranes. The probes were calibrated under physiological conditions (pH 6.4-7.8) and temperatures (22-38 °C), showing high stability, reproducibility of signals, and lack of interactions with biological solutes. Oxyphor G4 was used to dynamically image intravascular and interstitial oxygenation in murine tumors in vivo. The physiological relevance of the measurements was demonstrated by dynamically recording changes in tissue oxygenation during application of anesthesia (isofluorane). These experiments revealed that changes in isofluorane concentration significantly affect tissue oxygenation.
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Affiliation(s)
- Tatiana V Esipova
- Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
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Harms FA, de Boon WMI, Balestra GM, Bodmer SIA, Johannes T, Stolker RJ, Mik EG. Oxygen-dependent delayed fluorescence measured in skin after topical application of 5-aminolevulinic acid. JOURNAL OF BIOPHOTONICS 2011; 4:731-739. [PMID: 21770036 DOI: 10.1002/jbio.201100040] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2011] [Revised: 06/26/2011] [Accepted: 06/27/2011] [Indexed: 05/31/2023]
Abstract
Mitochondrial oxygen tension can be measured in vivo by means of oxygen-dependent quenching of delayed fluorescence of protoporphyrin IX (PpIX). Here we demonstrate that delayed fluorescence is readily observed from skin in rat and man after topical application of the PpIX precursor 5-aminolevulinic acid (ALA). Delayed fluorescence lifetimes respond to changes in inspired oxygen fraction and blood supply. The signals contain lifetime distributions and the fitting of rectangular distributions to the data appears more adequate than mono-exponential fitting. The use of topically applied ALA for delayed fluorescence lifetime measurements might pave the way for clinical use of this technique.
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Affiliation(s)
- Floor A Harms
- Department of Anesthesiology, Laboratory of Experimental Anesthesiology, ErasmusMC, University Medical Center Rotterdam, Rotterdam, The Netherlands
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Abstract
Early in the last century August Krogh embarked on a series of seminal studies to understand the connection between tissue metabolism and mechanisms by which the cardiovascular system supplied oxygen to meet those needs. Krogh recognized that oxygen was supplied from blood to the tissues by passive diffusion and that the most likely site for oxygen exchange was the capillary network. Studies of tissue oxygen consumption and diffusion coefficient, coupled with anatomical studies of capillarity in various tissues, led him to formulate a model of oxygen diffusion from a single capillary. Fifty years after the publication of this work, new methods were developed which allowed the direct measurement of oxygen in and around microvessels. These direct measurements have confirmed the predictions by Krogh and have led to extensions of his ideas resulting in our current understanding of oxygenation within the microcirculation. Developments during the last 40 years are reviewed, including studies of oxygen gradients in arterioles, capillaries, venules, microvessel wall and surrounding tissue. These measurements were made possible by the development and use of new methods to investigate oxygen in the microcirculation, so mention is made of oxygen microelectrodes, microspectrophotometry of haemoglobin and phosphorescence quenching microscopy. Our understanding of oxygen transport from the perspective of the microcirculation has gone from a consideration of oxygen gradients in capillaries and tissue to the realization that oxygen has the ability to diffuse from any microvessel to another location under the conditions that there exists a large enough PO(2) gradient and that the permeability for oxygen along the intervening pathway is sufficient.
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Affiliation(s)
- R N Pittman
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA 23298, USA.
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