Fiber Optic Oxygen Sensor Research Articles

Evaluation of Usefulness of Yeast-Based Biological Phantom and Preliminary Study for Verification of Hypoxic Effect of Flash Radiotherapy

As a basic hypothesis for the effectiveness of flash radiation therapy, the effect of preserving normal tissue during flash radiation is due to the instantaneous chemical depletion of oxygen. A yeast-based biological phantom was created to verify the hypoxic effect of flash radiation therapy. A study to upgrade the previously developed X-Band LINAC to a flash irradiation mode is in progress, and a preceding study is conducted to evaluate the usefulness of a yeast-based biological phantom manufactured by analyzing the change in oxygen by irradiating a high dose in a general radiation therapy device. Freeze-dried yeast sample (Saccharomyces cerevisiae, S288C) is activated and sub-cultured. For mass production of yeast samples, yeast culture medium is prepared by adding yeast colonies to the ypd medium. This study was conducted to verify the hypoxic effect among the biological mechanisms that occur during flash radiation therapy at the basic stage, and the oxygen concentration change during general radiation irradiation was measured in real time using a DO (Dissolved oxygen) meter and fiber optic sensor designed to do that. To prevent scatter, which is a concern during flash irradiation, the fiber form was used, and precise experiments are possible as a non-invasive oxygen concentration measurement method. Based on 10MV of general radiation therapy device, high-dose radiation of 500-10,000 cGy is irradiated to measure real-time oxygen concentration change. As a result of irradiation with high-dose (500-10,000 cGy) radiation of general LINAC, it was confirmed that the oxygen concentration of the yeast culture medium decreased by 5.7-63.2%, and the usefulness of the biological phantom fabricated based on the yeast culture medium was evaluated. Prior to the analysis of oxygen concentration change in yeast cells during X-Band LINAC flash irradiation, a preliminary study was conducted at a high dose in a general LINAC to obtain a significant result of oxygen concentration change and confirm the usefulness of the yeast-based biological phantom. Prior research was conducted and verified as a general irradiation experiment using a yeast-based biological phantom manufactured based on a DO meter and a fiber optic oxygen sensor. After irradiation with high-dose radiation, the oxygen concentration of the yeast culture medium was measured 5 times, and it was confirmed that there was a change in oxygen concentration of 5.7-63.2%, verifying the usefulness and stability of the biological phantom. The usefulness of the yeast-based biological phantom for high doses was confirmed, and it is expected that the usefulness of the biological phantom for flash radiation can be verified by additionally measuring the change in oxygen concentration of the biological phantom according to the high dose rate in the future.

Development and in-vivo validation of a portable phosphorescence lifetime-based fiber-optic oxygen sensor

Oxygenation is a crucial indicator of tissue viability and function. Oxygen tension (hbox {pO}_2), i.e. the amount of molecular oxygen present in the tissue is a direct result of supply (perfusion) and consumption. Thus, measurement of hbox {pO}_{{2}} is an effective method to monitor tissue viability. However, tissue oximetry sensors commonly used in clinical practice instead rely on measuring oxygen saturation (hbox {StO}_2), largely due to the lack of reliable, affordable hbox {pO}_2 sensing solutions. To address this issue we present a proof-of-concept design and validation of a low-cost, lifetime-based oxygen sensing fiber. The sensor consists of readily-available off-the shelf components such as a microcontroller, a light-emitting diode (LED), an avalanche photodiode (APD), a temperature sensor, as well as a bright in-house developed porphyrin molecule. The device was calibrated using a benchtop setup and evaluated in three in vivo animal models. Our findings show that the new device design in combination with the bright porphyrin has the potential to be a useful and accurate tool for measuring hbox {pO}_2 in tissue, while also highlighting some of the limitations and challenges of oxygen measurements in this context.

Preparation of a high stability optical fiber oxygen sensor based on the bilayer sensitive membrane

A high stability optical fiber oxygen sensor based on the bilayer sensitive membrane was presented, in which the sensitive membrane includes the sol–gel layer containing an oxygen sensitive indicator [Ru(phen)3]Cl2 and the nano-porous cellulose acetate coating wrapped around the sol–gel layer. The bilayer sensitive membrane had good permeability and resistance to reaction, which could protect the sol–gel oxygen sensing layer while ensuring permeability and improving probe stability. The scanning electron microscope (SEM) was used to characterize the morphology and thickness of the layers. The fluorescence of [Ru(phen)3]Cl2 could be dynamic quench when the oxygen contacts the fluorescent indicator by passing through the holes on the layers. The developed optical fiber oxygen sensor based on this bilayer sensitive membrane shows a wide linear detection range from 5 to 100 % with highly stability.

Research on a Fiber Optic Oxygen Sensor Based on All-Phase Fast Fourier Transform (apFFT) Phase Detection.

Fiber optic oxygen sensors based on fluorescence quenching play an important role in oxygen sensors. They have several advantages over other methods of oxygen sensing—they do not consume oxygen, have a short response time and are of high sensitivity. They are often used in special environments, such as hazardous environments and in vivo. In this paper, a new fiber optic oxygen sensor is introduced, which uses the all-phase fast Fourier transform (apFFT) algorithm, instead of the previous lock-in amplifier, for the phase detection of excitation light and fluorescence. The excitation and fluorescence frequency was 4 KHz, which was conducted between the oxygen-sensitive membrane and the photoelectric conversion module by the optical fiber and specially-designed optical path. The phase difference of the corresponding oxygen concentration was obtained by processing the corresponding electric signals of the excitation light and the fluorescence. At 0%, 5%, 15%, 21% and 50% oxygen concentrations, the experimental results showed that the apFFT had good linearity, precision and resolution—0.999°, 0.05° and 0.0001°, respectively—and the fiber optic oxygen sensor with apFFT had high stability. When the oxygen concentrations were 0%, 5%, 15%, 21% and 50%, the detection errors of the fiber optic oxygen sensor were 0.0447%, 0.1271%, 0.3801%, 1.3426% and 12.6316%, respectively. Therefore, the sensor that we designed has greater accuracy when measuring low oxygen concentrations, compared with high oxygen concentrations.

Blood Oxygen Sensor Using a Boron-Doped Diamond Electrode.

The electrochemical behavior of oxygen (O2) in blood was studied using boron-doped diamond (BDD) electrodes. Cyclic voltammogram of O2 in a 0.1 M phosphate buffer solution solution containing 1 × 10-6 M of bovine hemoglobin exhibits a reduction peak at -1.4 V (vs Ag/AgCl). Moreover, the scan rate dependence was investigated to study the reduction reaction mechanism, which was attributable to the reduction of O2 to H2O2 via two electrons. A linear calibration curve was observed in the concentration range of 86.88-314.63 mg L-1 (R2 = 0.99) with a detection limit of 1.0 mg L-1 (S/B = 3). The analytical performance was better than those with glassy carbon or platinum electrodes as the working electrode. In addition, an application to bovine blood was performed. The O2 concentration in the blood measured on the BDD electrodes was compared to that measured using an OxyLite Pro fiber-optic oxygen sensor device. Both methods gave similar values of the O2 concentration in the range of ∼40 to 150 mmHg. This result confirms that BDD electrodes could potentially be used to detect the O2 concentration in blood.

Comment on: “Dissolved oxygen sensing characteristics of plastic optical fiber coated with hydrogel film” – The wider context of fibre optic oxygen sensing

A recently published article by Bian et al. (2021) presents a novel plastic optical fibre coated with hydrogel film to measure dissolved oxygen via luminescence quenching. The article concludes that “The sensor with biocompatible material is expected to be applied to the monitor of dissolved oxygen in the domain of biomedicine”. However, the oxygen sensor presented contains ruthenium, a toxic material that is considered unsafe for clinical applications. It is unclear whether the hydrogel film coating may be sufficient to prevent direct contact between ruthenium and human tissue in clinical applications. However, platinum porphyrin has been used in fibre optic oxygen sensors in pre-clinical applications. This Comment article provides a brief overview of some platinum porphyrin-based fibre optic oxygen sensors that, despite an advanced degree of maturity and biocompatibility, were overlooked in the recently published article.

Response to the comment on: “Dissolved oxygen sensing characteristics of plastic optical fiber coated with hydrogel film” – The wider context of fibre optic oxygen sensing

In, F. Formenti (2021) proposed that ruthenium complexes, as an unsafe and toxic material, are not suitable for clinical applications and indicated that platinum porphyrin has been clinically applied to optical fiber oxygen sensors with short response time. This article will answer the questions raised by F. Formenti from the following aspects: 1.The toxicity of ruthenium complexes was overestimated. This article will briefly outline some biomedical applications based on ruthenium. 2. Hydrogels have been used in different biomedicine purpose, the ruthenium indicator in this article [2] will not leak from the polymer network structure hydrogel. 3. The response time in this article [2] is shorter than reported and the sensing system [2] has other excellent properties.

Bedside monitoring of lung volume available for gas exchange

BackgroundBedside measurement of lung volume may provide guidance in the personalised setting of respiratory support, especially in patients with the acute respiratory distress syndrome at risk of ventilator-induced lung injury. We propose here a novel operator-independent technique, enabled by a fibre optic oxygen sensor, to quantify the lung volume available for gas exchange. We hypothesised that the continuous measurement of arterial partial pressure of oxygen (PaO2) decline during a breath-holding manoeuvre could be used to estimate lung volume in a single-compartment physiological model of the respiratory system.MethodsThirteen pigs with a saline lavage lung injury model and six control pigs were studied under general anaesthesia during mechanical ventilation. Lung volumes were measured by simultaneous PaO2 rate of decline (VPaO2) and whole-lung computed tomography scan (VCT) during apnoea at different positive end-expiratory and end-inspiratory pressures.ResultsA total of 146 volume measurements was completed (range 134 to 1869 mL). A linear correlation between VCT and VPaO2 was found both in control (slope = 0.9, R2 = 0.88) and in saline-lavaged pigs (slope = 0.64, R2 = 0.70). The bias from Bland–Altman analysis for the agreement between the VCT and VPaO2 was − 84 mL (limits of agreement ± 301 mL) in control and + 2 mL (LoA ± 406 mL) in saline-lavaged pigs. The concordance for changes in lung volume, quantified with polar plot analysis, was − 4º (LoA ± 19°) in control and − 9° (LoA ± 33°) in saline-lavaged pigs.ConclusionBedside measurement of PaO2 rate of decline during apnoea is a potential approach for estimation of lung volume changes associated with different levels of airway pressure.

Preliminary experimental study on the influence of different tidal volume and frequency of normal minute ventilation on the dynamic changes of carotid blood oxygen in living goats

Objective: On the basis of preliminarily verifying the use of ultra-fast reaction polymer matrix optical fiber oxygen sensor and its measuring system to record the continuous and dynamic changes of carotid artery oxygen partial pressure (PaO2), in order to analyze and discuss the influence of lung ventilation on the continuous and dynamic changes of PaO2, we designed a whole animal experimental study in vivo. Methods: Four hybrid goats were selected, and the skin was cut and exposed directly under general anesthesia and tracheal intubation. The oxygen sensor, connected with the measuring system, was inserted directly into the left carotid artery to continuously record the dynamic changes of PaO2. With normal minute ventilation,mechanical ventilation is implemented through three tidal volumes: normal tidal volume (VT=15 ml/kg, Rf=20 bpm), half tidal volume (halved VT, doubled Rf) and double tidal volume (doubled VT, halved Rf). Each tidal volume was stable for 10~15 min respectively. We analyzed and calculated the average values of PaO2, the fluctuation magnitudes of PaO2 changes between breaths of last 180 s and the delay times of lung-carotid artery were. We analyzed the effects of different tidal volumes. Results: The heart rate and blood pressure of living goats were maintained stable during the mechanical ventilation experiment with normal ventilation volume Lung-carotid artery delay time is 1.4~1.8 s (about 3 heartbeats at this time). Under normal tidal volume of mechanical ventilation, the average value of PaO2 was (102.94±2.40, 99.38~106.16) mmHg, and the fluctuation range was (21.43±1.65, 19.21~23.59) mmHg, accounting for (20.80± 1.34, 18.65~22.22)% of the average value. Under the condition of halving tidal volume, the average value of PaO2 was maintained at (101.01±4.25, 94.09~105.66) mmHg, which was slightly decreased but not significant (P>0.05 compared with normal mechanical ventilation), but the fluctuation range of PaO2 was significantly reduced to (18.14±1.43, 16.46~20.05) mmHg, accounting for 17.5% of the average value. Under double tidal volume mechanical ventilation, although the average value of PaO2 increased slightly remained at (106.42±4.74, 101.19~114.08) mmHg (P>0.05 compared with normal mechanical ventilation and P<0.05 compared with half tidal volume mechanical ventilation), the fluctuation magnitude of PaO2 increased significantly to (26.58±1.88, 23.46~28.46)mmHg. Conclusion: Inspiration and expiration of normal lung ventilation are the initial factors for the increase and decrease of PaO2 in carotid artery. Under normal ventilation, halving tidal volume and doubling tidal volume significantly changed the fluctuation magnitude of PaO2, but the average value of PaO2 changed only slightly, while the lung-carotid delay time was similar.

Optimization of All-Polymer Optical Fiber Oxygen Sensors with Antenna Dyes and Improved Solvent Selection Using Hansen Solubility Parameters.

We present an all-polymer optical fiber sensor for the sensing of dissolved oxygen by phase-fluorometry. The sensing matrix is applied as a film on the fiber end-surface, and consists of poly-methylmethacrylate (PMMA), the oxygen quenchable luminophore platinum-octaethylporphyrin (PtOEP) and the luminophore coumarin 545T for increasing the brightness of PtOEP by way of resonance energy transfer (RET), also called light harvesting. We show that by using Hansen Solubility Parameters (HSPs), it is possible to quantitatively formulate a solvent mixture with a good solubility of the polymer matrix and the luminophores simultaneously. Our approach can readily be extended to other polymers and luminophores and is therefore a valuable tool for researchers working with photoluminescence and polymeric matrices.

Cardio-centric hemodynamic management improves spinal cord oxygenation and mitigates hemorrhage in acute spinal cord injury

Chronic high-thoracic and cervical spinal cord injury (SCI) results in a complex phenotype of cardiovascular consequences, including impaired left ventricular (LV) contractility. Here, we aim to determine whether such dysfunction manifests immediately post-injury, and if so, whether correcting impaired contractility can improve spinal cord oxygenation (SCO2), blood flow (SCBF) and metabolism. Using a porcine model of T2 SCI, we assess LV end-systolic elastance (contractility) via invasive pressure-volume catheterization, monitor intraparenchymal SCO2 and SCBF with fiberoptic oxygen sensors and laser-Doppler flowmetry, respectively, and quantify spinal cord metabolites with microdialysis. We demonstrate that high-thoracic SCI acutely impairs cardiac contractility and substantially reduces SCO2 and SCBF within the first hours post-injury. Utilizing the same model, we next show that augmenting LV contractility with the β-agonist dobutamine increases SCO2 and SCBF more effectively than vasopressor therapy, whilst also mitigating increased anaerobic metabolism and hemorrhage in the injured cord. Finally, in pigs with T2 SCI survived for 12 weeks post-injury, we confirm that acute hemodynamic management with dobutamine appears to preserve cardiac function and improve hemodynamic outcomes in the chronic setting. Our data support that cardio-centric hemodynamic management represents an advantageous alternative to the current clinical standard of vasopressor therapy for acute traumatic SCI.

Quantifying Oxygen Levels in 3D Bioprinted Cell-Laden Thick Constructs with Perfusable Microchannel Networks.

The survival and function of thick tissue engineered implanted constructs depends on pre-existing, embedded, functional, vascular-like structures that are able to integrate with the host vasculature. Bioprinting was employed to build perfusable vascular-like networks within thick constructs. However, the improvement of oxygen transportation facilitated by these vascular-like networks was directly quantified. Using an optical fiber oxygen sensor, we measured the oxygen content at different positions within 3D bioprinted constructs with and without perfusable microchannel networks. Perfusion was found to play an essential role in maintaining relatively high oxygen content in cell-laden constructs and, consequently, high cell viability. The concentration of oxygen changes following switching on and off the perfusion. Oxygen concentration depletes quickly after pausing perfusion but recovers rapidly after resuming the perfusion. The quantification of oxygen levels within cell-laden hydrogel constructs could provide insight into channel network design and cellular responses.

Noninvasive Fluorine-19 Magnetic Resonance Relaxometry Measurement of the Partial Pressure of Oxygen in Acellular Perfluorochemical-loaded Alginate Microcapsules Implanted in the Peritoneal Cavity of Nonhuman Primates.

We have utilized a noninvasive technique for measuring the partial pressure of oxygen (pO2) in alginate microcapsules implanted intraperitoneally in healthy nonhuman primates (NHPs). Average pO2 is important for determining if a transplant site and capsules with certain passive diffusion characteristics can support the islet viability, metabolic activity, and dose necessary to reverse diabetes. Perfluoro-15-crown-5-ether alginate capsules were infused intraperitoneally into 3 healthy NHPs. Peritoneal pO2 levels were measured on days 0 and 7 using fluorine-19 magnetic resonance relaxometry and a fiber-optic probe. Fluorine-19 MRI was used to determine the locations of capsules within the peritoneal space on days 0 and 7. Gross and histologic evaluations of the capsules were used to assess their biocompatibility postmortem. At day 0 immediately after infusion of capsules equilibrated to room air, capsules were concentrated near the infusion site, and the pO2 measurement using magnetic resonance relaxometry was 147 ± 9 mm Hg. On day 7 after capsules were dispersed throughout the peritoneal cavity, the pO2 level was 61 ± 11 mm Hg. Measurements using the fiber-optic oxygen sensor were 132 ± 7.5 mm Hg (day 0) and 89 ± 6.1 mm Hg (day 7). Perfluoro-15-crown-5-ether capsules retrieved on day 7 were intact and free-floating without host cell attachment, although the numbers of peritoneal CD20 B cells, CD4 and CD8 T cells, and CD14 macrophages increased consistent with a mild foreign body reaction. The peritoneal pO2 of normal NHPs is relatively low and we predict would decrease further when encapsulated islets are transplanted intraperitoneally.

Fibre optic oxygen sensor for long term use in jet fuel, featuring phosphorescent dye chemically bonded to functionalised silica

Five new compounds, termed “metallo-porphyrin silicas”, have been synthesised by the reaction of functionalised silicas with platinum (II) meso tetrakis (pentafluorophenyl) porphyrin. The reaction resulted in the elimination of hydrogen fluoride to create a covalent bond between a functional group of the silica and the para carbon atom of a pentafluorophenyl group. Four out of the five new compounds exhibited phosphorescence under irradiation with u.v. light at ~400 nm, and in all four cases the phosphorescence was quenched by molecular oxygen. Stern Volmer plots of the four phosphorescent compounds showed that the aminopropyl derivative gave the largest response at 400 nm over a concentration range of 0–20% oxygen. Further tests were undertaken on this compound that showed that the output was dependant not only on oxygen concentration but also temperature (−17 °C–40 °C). A prototype probe suitable for testing oxygen content in aviation fuels was developed using an optical fibre. It was possible to detect changes in oxygen concentration in jet fuel. The results demonstrate the potential of this approach to provide a low cost, low power resilient probe for the detection of oxygen in aviation fuel.

Placental oxygen transfer reduces hypoxia-reoxygenation swings in fetal blood in a sheep model of gestational sleep apnea.

Obstructive sleep apnea (OSA), characterized by events of hypoxia-reoxygenation, is highly prevalent in pregnancy, negatively affecting the gestation process and particularly the fetus. Whether the consequences of OSA for the fetus and offspring are mainly caused by systemic alterations in the mother or by a direct effect of intermittent hypoxia in the fetus is unknown. In fact, how apnea-induced hypoxemic swings in OSA are transmitted across the placenta remains to be investigated. The aim of this study was to test the hypothesis, based on a theoretical background on the damping effect of oxygen transfer in the placenta, that oxygen partial pressure (Po2) swings resulting from obstructive apneas mimicking OSA are mitigated in the fetal circulation. To this end, four anesthetized ewes close to term pregnancy were subjected to obstructive apneas consisting of 25-s airway obstructions. Real-time Po2 was measured in the maternal carotid artery and in the umbilical vein with fast-response fiber-optic oxygen sensors. The amplitudes of Po2 swings in the umbilical vein were considerably smaller [3.1 ± 1.0 vs. 21.0 ± 6.1 mmHg (mean ± SE); P < 0.05]. Corresponding estimated swings in fetal and maternal oxyhemoglobin saturation tracked Po2 swings. This study provides novel insights into fetal oxygenation in a model of gestational OSA and highlights the importance of further understanding the impact of sleep-disordered breathing on fetal and offspring development.NEW & NOTEWORTHY This study in an airway obstruction sheep model of gestational sleep apnea provides novel data on how swings in oxygen partial pressure (Po2) translate from maternal to fetal blood. Real-time simultaneous measurement of Po2 in maternal artery and in umbilical vein shows that placenta transfer attenuates the magnitude of oxygenation swings. These data prompt further investigation of the extent to which maternal apneas could induce similar direct oxidative stress in fetal and maternal tissues.

Spittlebugs snorkel in cuckoo spit

In the lexicon of garden pests, spittlebugs (Philaenus spumarius) are probably one of the least offensive. Sipping sap destined for a plant's leaves, the tiny spittlebug nymphs do not linger long; yet, the foam that covers them – known euphemistically as cuckoo spit – drives gardeners wild. However, when Philip Matthews moved from Australia to Vancouver, Canada, the frothy blobs dotted across the city during spring transfixed him. ‘I'd never been anywhere where they were so abundant’, he laughs. He also realised that the froth-encrusted insects are essentially manufacturing their own aquatic environment. ‘Some of my previous research had been looking at aquatic insects carrying bubbles of air to breathe while underwater’, recalls Matthews. Which got him wondering: how could the bugs breathe while lathered in bubbles? Were they inhaling air trapped in the foam or poking their abdomens out of the frothy blanket to breathe?To answer these questions, undergraduate Kephra Beckett located cuckoo spit on shrubs in the University of British Columbia (UBC) campus and carefully poked a tiny fibre-optic oxygen sensor into the edge of a blob, recording the amount of oxygen as she painstakingly moved the sensor through the foam. ‘We never saw sub-atmospheric levels of oxygen in the centre of the spittle mass as you'd expect if the bug was breathing oxygen from the surrounding bubbles’, says Matthews. In addition, when Beckett measured the insects’ oxygen consumption in the lab, she could clearly see their abdomens protruding from the bubbles, unless they were startled. Then, they dived beneath the foam and their oxygen consumption ceased until they re-emerged minutes later.So the nymphs weren't using their foam bubbles as an aqualung, they were snorkelling. However, Matthews knew that during their final life stage, before metamorphosing into adults, spittlebugs produce a larger bubble chamber by popping the surrounding bubbles. Might they be consuming the oxygen in the enlarged chamber during their final moult? Collecting youngsters on the verge of the transition, complete with foliage residences, and returning to the lab, Beckett cautiously inserted the oxygen sensor into the bubble chamber and found that the oxygen concentration was about 10% lower than that of the external atmosphere, suggesting that they were breathing the oxygen within. Her colleague Anne Robertson also sandwiched young spittlebugs between a microscope slide and a coverslip, to find out if they could resort to breathing the air trapped in the foam, and saw the youngsters puncturing the bubbles with their abdomens. In addition, when she coated the microscope slide with an oxygen-sensitive dye, she could see the dye glow intensely as the oxygen declined. The tiny nymphs are able to use their bubbles as an aqualung when necessary.In addition, Beckett and Matthews were curious to find out just how hard it is for the nymphs to dine on dilute xylem sap. According to Matthews, the sap is under negative pressure – air gets drawn into the sap channels when they are punctured – making it hard for spittlebugs to suck against. The question was, how hard? Back in the lab, Beckett recorded the carbon dioxide produced by the patiently waiting nymphs, before providing them with juicy sheep sorrel plants and rerecording their carbon dioxide production as they gorged on sap and spewed out foam. However, the insects' carbon dioxide production only increased by a modest 20%. ‘That was a big surprise’, says Matthews. ‘It's not much greater than their cost of walking’, he adds.So, spittlebugs appear not to be struggling to take a sip, but Matthews suspects that there may be more to the story and is looking forward to next spring when splodges of cuckoo spit begin bubbling up all over Vancouver again.

Experimental research on fiber optic oxygen sensor based on fluorescence quenching principle

基于荧光淬灭原理的光纤氧传感器一直是许多研究工作的重点。介绍了一种制作简单、成本低的光纤氧传感器制造方法。该方法基于荧光淬灭原理，在光纤末端涂覆荧光材料铂八乙基卟啉(PtOEP)实现的。传感器中荧光材料被395nm的紫光激发，并由Y形光纤引导，使用广州犀谱光电USB2000+光谱仪记录荧光的发光强度时序图。最后得到的PtOEP的(<i>I</i>₀/<i>I</i>₁₀₀)-1的值为0.78，即光纤氧传感器的灵敏度为0.78，而且，斯特恩-沃尔默(Stern-Volmer)图显示出很好的线性特性。从氧气到空气环境的响应时间为24 s，从空气环境到氧气的响应时间是5 s。结果表明，基于荧光淬灭原理的光纤氧传感器具有较高的灵敏度和更快的响应时间。

Development of a fibre optic oxygen sensor for respiratory monitoring in the intensive care unit

Arterial oxygen tension is commonly measured by means of intermittent arterial gas sampling. This technique is unable to detect within-breath oxygen tension changes that may be observed in mechanically ventilated patients, especially in the presence of lung injury. Moreover, it may not afford sufficient time resolution to detect potentially injurious settings of the mechanical ventilation itself. Continuous and rapid arterial oxygen tension measurement could detect within-breath changes in pulmonary gas exchange and offer clinically important feedback for the management of mechanical ventilation therapy in real time. We developed a novel fibre optic intravascular oxygen tension sensor, measured its fast response time in vitro, tested its blood clotting resistance over a period of 24 hours, and its capacity to measure arterial oxygen tension in vivo in a pig model of uninjured lung. This short communication will review the main steps of this collaborative project’s progress to date, highlighting the technology’s strengths, together with future potential for translation to a clinical scenario.

Effects of hypoxic preconditioning on neuroblastoma tumour oxygenation and metabolic signature in a chick embryo model

Hypoxia episodes and areas in tumours have been associated with metastatic dissemination and poor prognosis. Given the link between tumour tissue oxygen levels and cellular metabolic activity, we hypothesised that the metabolic profile between metastatic and non-metastatic tumours would reveal potential new biomarkers and signalling cues. We have used a previously established chick embryo model for neuroblastoma growth and metastasis, where the metastatic phenotype can be controlled by neuroblastoma cell hypoxic preconditioning (3 days at 1% O2). We measured, with fibre-optic oxygen sensors, the effects of the hypoxic preconditioning on the tumour oxygenation, within tumours formed by SK-N-AS cells on the chorioallantoic membrane (CAM) of chick embryos. We found that the difference between the metastatic and non-metastatic intratumoural oxygen levels was small (0.35% O2), with a mean below 1.5% O2 for most tumours. The metabolomic profiling, using NMR spectroscopy, of neuroblastoma cells cultured in normoxia or hypoxia for 3 days, and of the tumours formed by these cells showed that the effects of hypoxia in vitro did not compare with in vivo tumours. One notable difference was the high levels of the glycolytic end-products triggered by hypoxia in vitro, but not by hypoxia preconditioning in tumours, likely due to the very high basal levels of these metabolites in tumours compared with cells. In conclusion, we have identified high levels of ketones (3-hydroxybutyrate), lactate and phosphocholine in hypoxic preconditioned tumours, all known to fuel tumour growth, and we herein point to the poor relevance of in vitro metabolomic experiments for cancer research.

Oxygen Concentration Measurement in the Porous Cathode of Aqueous Lithium–Air Battery By Fine Optical Fiber

Spatial and temporal oxygen concentration distribution in the porous cathode of discharging aqueous lithium-air secondary battery was successfully measured. Lithium-air battery attracts great attention because of its high energy density. In this study, we focus on the aqueous lithium–air secondary battery. The aqueous electrolyte realizes cost reduction and ensures the safe use of a battery. On the other hand, low solubility of oxygen in aqueous electrolyte limits oxygen transport to the reaction site. To realize a more powerful aqueous lithium–air battery, it is necessary to clarify and improve the oxygen transport phenomena in the porous cathode. In this study, we developed the measurement technique of oxygen concentration in the porous cathode under operating condition by inserting a fine optical fiber oxygen sensor. In this study, platinum tetrakis pentrafluoropheny porphine (PtTFPP) was employed as oxygen indicator [1]. When the PtTFPP is exposed to excitation light (λ = 405 nm), phosphorescence emission (λ= 650 nm) is produced, and its intensity depends on oxygen partial pressure. Thus, quantitative oxygen concentration can be obtained by measuring phosphorescence intensity and using calibration data. The PtTFPP was painted at the edge of optical fiber of which diameter was 110 μm. In order to measure the phosphorescence intensity, bifurcated optical fibers were connected to excitation light source and spectrometer, respectively. As shown in Figure 1, phosphorescence intensity changed at 650 nm depending on oxygen concentration. The experimental setup is shown in Figure 2. The porous cathode (SIGRACET® 10AA, SGL Group, USA) was fixed near electrolyte interface horizontally. The tiny optical fiber sensor was moved up and inserted in the cathode. The temporal oxygen concentration change from the start of discharge was measured at arbitrary positions in the porous cathode. The composite anode was water-stable and had a multilayer structure for the aqueous lithium air battery [2]. Measurement of spatial and temporal distribution of oxygen concentration has been conducted under the assumption that discharge experiment had reproducibility. Initial position (z = 0 μm) was defined arbitrary, and the sensor was moved up each 70 μm. Time variation of oxygen concentration was measured at each point. Finally, spatiotemporal distribution of oxygen concentration for each current density was obtained. As shown in Figure 3, the spatial and temporal oxygen concentration distribution at 0.10 mA/cm2 was successfully observed. When the discharge was started, the oxygen concentration gradually decreased in the cathode, and finally, oxygen concentration reached considerably low value even in the condition of 0.10 mA/cm2. In this experiment, oxygen concentration gradients are present at both ends of the atmosphere side (0-140 μm) and electrolyte side (490-910 μm) of the cathode. Flux for both side of cathode, upper side and lower side, was discussed and comprehensible interpretation was obtained. Although dissolved oxygen that forms flux from the lower side of cathode has an effective supply to the porous electrode, electrolyte layer formed at between the atmosphere and the cathode causes oxygen transport resistance. Acknowledgement: This work was supported by JSPS KAKENHI Grant Number 15K13881, 15H02347. Reference: [1] CS Chu., CA Lin, Sensors and Actuators B: Chemica, 2014, 195, 259-265. [2] T. Zhang, N. Imanishi, S. Hasegawa, A. Hirano, J. Xie, Y. Takeda, O. Yamamoto, N. Sammes, J. Electrochem. Soc., 2008, 155, A965. Figure 1