Optical Oxygen Research Articles

Materials for optical oxygen sensing under high hydrostatic pressure

Optical oxygen sensors based on indicators immobilized into porous and nonporous matrix materials were investigated in regard to their sensing behaviour under high hydrostatic pressure. The sensors were subjected to step-wise pressure increase up to approximately 200 bar in multiple cycles using a custom-made chamber. The investigated materials are based on oxygen indicators (a platinum(II) benzoporphyrin dye and ruthenium(II) polypyridyl complexes) immobilized in microparticles: silica gels of different porosities, controlled pore glass, poly(phenylsilsesquioxane), crosslinked polystyrene, the metal-organic frameworks ZIF-8 and UiO-66. The microparticles are in turn dispersed in highly oxygen-permeable silicone and Hyflon AD matrices. Homogeneous films of dye doped polystyrene and polyurethane hydrogels as well as non-porous polystyrene nanospheres directly dispersed in water were used for comparison purposes. All the porous materials were found to be stable under elevated hydrostatic pressure. Although the actual oxygen concentration remained unchanged upon increasing pressure, the sensors demonstrated an apparent decrease of calculated oxygen concentration (between −0.02 and −0.45 mg O2 L-1 H2O per 100 bar), which was fully reversible. Furthermore, the kinetics of the pressure response of the sensors was determined in experiments with high temporal resolution. Spikes attributed to pressure-induced oxygen diffusion between sensor components were observed within the first seconds after pressurization/depressurization.

Comparison of the Effects of Normocapnia and Mild Hypercapnia on the Optic Nerve Sheath Diameter and Regional Cerebral Oxygen Saturation in Patients Undergoing Gynecological Laparoscopy with Total Intravenous Anesthesia.

Cerebral hemodynamics may be altered by hypercapnia during a lung-protective ventilation (LPV), CO2 pneumoperitoneum, and Trendelenburg position during general anesthesia. The purpose of this study was to compare the effects of normocapnia and mild hypercapnia on the optic nerve sheath diameter (ONSD), regional cerebral oxygen saturation (rSO2), and intraoperative respiratory mechanics in patients undergoing gynecological laparoscopy under total intravenous anesthesia (TIVA). Sixty patients (aged between 19 and 65 years) scheduled for laparoscopic gynecological surgery in the Trendelenburg position. Patients under propofol/remifentanil total intravenous anesthesia were randomly assigned to either the normocapnia group (target PaCO2 = 35 mmHg, n = 30) or the hypercapnia group (target PaCO2 = 50 mmHg, n = 30). The ONSD, rSO2, and respiratory and hemodynamic parameters were measured at 5 min after anesthetic induction (Tind) in the supine position, and at 10 min and 40 min after pneumoperitoneum (Tpp10 and Tpp40, respectively) in the Trendelenburg position. There was no significant intergroup difference in change over time in the ONSD (p = 0.318). The ONSD increased significantly at Tpp40 when compared to Tind in both normocapnia and hypercapnia groups (p = 0.02 and 0.002, respectively). There was a significant intergroup difference in changes over time in the rSO2 (p < 0.001). The rSO2 decreased significantly in the normocapnia group (p = 0.01), whereas it increased significantly in the hypercapnia group at Tpp40 compared with Tind (p = 0.002). Alveolar dead space was significantly higher in the normocapnia group than in the hypercapnia group at Tpp40 (p = 0.001). In conclusion, mild hypercapnia during the LPV might not aggravate the increase in the ONSD during CO2 pneumoperitoneum in the Trendelenburg position and could improve rSO2 compared to normocapnia in patients undergoing gynecological laparoscopy with TIVA.

Optical Oxygen Sensor Patch Printed with Polystyrene Microparticles-based Ink on Flexible Substrate.

Optical oxygen sensors based on photoluminescence quenching have gained increasing attention as a superior method for continuous monitoring of oxygen in a growing number of applications. A simple and low-cost fabrication technique was developed to produce sensor arrays capable of two-dimensional oxygen tension measurement. Sensor patches were printed on polyvinylidene chloride film using an oxygen-sensitive ink cocktail, prepared by immobilizing Pt(II) mesotetra(pentafluorophenyl)porphine (PtTFPP) in monodispersed polystyrene microparticles. The dispersion media of the ink cocktail, high molecular weight polyvinyl pyrrolidone suspended in 50% ethanol (v/v in water), allowed adhesion promotion and compatibility with most common polymeric substrates. Ink phosphorescence intensity was found to vary primarily with fluorophore concentration and to a lesser extent with polystyrene particle size. The sensor performance was investigated as a function of oxygen concentrations employing two different techniques: a multi-frequency phase fluorometer and smart phone-based image acquisition. The printed sensor patch showed fast and repetitive response over 0-21% oxygen concentrations with high linearity (with R2 >0.99) in a Stern-Volmer plot, and sensitivity of I0/I21 >1.55. The optical sensor response on a surface was investigated further using two-dimensional images which were captured and analyzed under different oxygen environment. Printed sensor patch along with imaging read-out technique make an ideal platform for early detection of surface wounds associated with tissue oxygen.

Measurement of oxygen concentrations and oxygen consumption rates using an optical oxygen sensor, and its application in hypoxia-related research in highly eutrophic coastal regions

To confirm the usefulness of optical oxygen sensors in hypoxia-related research in coastal regions, a contactless optical sensor (COS) (FireStingO2, Pyroscience) was used to measure dissolved oxygen concentrations, and the values obtained were compared with those obtained using the traditional Winkler method. During spring and summer seasons, bottom water samples from the Mikawa Bay, where hypoxia frequently occurs, were analyzed. The correlation between the oxygen concentrations obtained using the COS and Winkler methods had a slope of 1.01, an intercept of −6.17 μmol kg−1, and a coefficient of determination of 0.97. Further, when the oxygen consumption rates in the bottom water (OCRbw) were measured using these two methods, the slope, intercept, and coefficient of determination of the correlation between these values were 1.05, −0.08 μmol kg−1 d−1, and 0.63, respectively. These findings indicate that the COS method is suitable for obtaining accurate oxygen concentrations as well as OCRbw values for coastal waters, but it is still difficult to adapt it to small OCRbw values in the open ocean. The highest OCRbw (38.3 μmol kg−1 d−1) was observed at the inner part of the Bay in the end of August. Furthermore, the COS method also allowed the measurement of oxygen concentrations in the water overlaying the sediment core (OCRs + w), which in the Mikawa Bay were 3–5-fold higher than the corresponding OCRbw values. Observations made using the COS method in the Upper Gulf of Thailand (UGoT), which is also characterized by a highly hypoxic bottom layer, showed high OCRbw (>30 μmol kg−1 d−1) and OCRs + w (>40 μmol kg−1 d−1) near the estuarine of large rivers not in the rainy season but also in the dry season. The COS method has potential for use in the collection of OCR data that can significantly contribute to the accuracy of hypoxia prediction models.

PtOEP-PDMS-Based Optical Oxygen Sensor.

The advanced and widespread use of microfluidic devices, which are usually fabricated in polydimethylsiloxane (PDMS), requires the integration of many sensors, always compatible with microfluidic fabrication processes. Moreover, current limitations of the existing optical and electrochemical oxygen sensors regarding long-term stability due to sensor degradation, biofouling, fabrication processes and cost have led to the development of new approaches. Thus, this manuscript reports the development, fabrication and characterization of a low-cost and highly sensitive dissolved oxygen optical sensor based on a membrane of PDMS doped with platinum octaethylporphyrin (PtOEP) film, fabricated using standard microfluidic materials and processes. The excellent mechanical and chemical properties (high permeability to oxygen, anti-biofouling characteristics) of PDMS result in membranes with superior sensitivity compared with other matrix materials. The wide use of PtOEP in sensing applications, due to its advantage of being easily synthesized using microtechnologies, its strong phosphorescence at room temperature with a quantum yield close to 50%, its excellent Strokes Shift as well as its relatively long lifetime (75 µs), provide the suitable conditions for the development of a miniaturized luminescence optical oxygen sensor allowing long-term applications. The influence of the PDMS film thickness (0.1–2.5 mm) and the PtOEP concentration (363, 545, 727 ppm) in luminescent properties are presented. This enables to achieve low detection levels in a gas media range from 0.5% up to 20%, and in liquid media from 0.5 mg/L up to 3.3 mg/L at 1 atm, 25 °C. As a result, we propose a simple and cost-effective system based on a LED membrane photodiode system to detect low oxygen concentrations for in situ applications.

Hydrogen in nonstoichiometric cubic titanium monoxides: X-ray and neutron diffraction, neutron vibrational spectroscopy and NMR studies

Hydrogen-induced changes in the properties of transition-metal oxides have attracted much recent attention due to numerous applications of these materials including catalysis, H2 production, low-temperature H2 sensing, solar cells, and air purification. However, basic properties of hydrogenated titanium monoxides have not been investigated so far. In the present work, we report the results of the first studies of the crystal structure, vibrational spectra, and mobility of H atoms in TiO0.72H0.30 and TiO0.96H0.14 using X-ray diffraction (XRD), neutron powder diffraction, neutron vibrational spectroscopy, and nuclear magnetic resonance (NMR). The hydrogenated compound TiO0.72H0.30 is found to retain the disordered cubic B1-type structure of the initial titanium monoxide, where H atoms exclusively occupy vacancies in the oxygen sublattice. It has been revealed that hydrogenation of the disordered cubic TiO0.96 leads to the formation of the two-phase compound TiO0.96H0.14, where the disordered B1-type phase coexists with the monoclinic phase of Ti5O5 type with an ordered arrangement of vacancies. In both phases, H atoms are found to occupy only vacancies in the oxygen sublattice. The low-temperature inelastic neutron scattering spectra of TiO0.72H0.30 and TiO0.96H0.14 in the energy transfer range of 40–180 meV exhibit a single peak due to optical oxygen vibrations (centered on about 60 meV) and a broad structure at 90–170 meV due to optical H vibrations. The unusual width of this structure can be attributed to the broken symmetry of hydrogen sites in the titanium monoxides: because of the presence of vacancies in the titanium sublattice, the actual point symmetry of these sites appears to be lower than octahedral. Proton NMR measurements have revealed that both hydrogenated compounds are metallic; no signs of hydrogen diffusive motion in TiO0.72H0.30 and TiO0.96H0.14 at the frequency scale of about 105 s-1 have been found up to 370 K.

Multifunctional derivatives of donor-substituted perfluorobiphenyl for OLEDs and optical oxygen sensors

New donor-acceptor and donor-acceptor-donor compounds based on perfluorobiphenyl electron acceptor and diphenylamine or carbazole as electron-donating units were designed, synthesized and characterized. The influence of the nature and number of electron-donating units on thermal, electrochemical and photophysical properties was studied. The compounds exhibited photoluminescence ranging from near-UV to green region. The solid samples of the compounds demonstrated photoluminescence quantum yields in the range from 0.1 to 0.51.2,7-Dimethoxycarbazole-containing compound was characterized by negligible energy gaps between the lowest singlet and triplet states (0.1 eV) and subsequently showed thermally activated delayed fluorescence (TADF). Carbazolyl-substituted perfluorobiphenyl derivatives showed aggregation-induced emission enhancement and high values of the energies of triplet levels (up to 3.08 eV). The derivatives exhibited from moderate to high temperatures of 5% weight loss up to 356 °C. Electron mobility up to 1.2 × 10−4 cm2 V−1 s−1 at electric field of 7 × 105 V/cm was detected for the studied compounds by time-of-flight measurements. One compound with the best combination of the required properties for the OLED hosts was selected for the fabrication of green TADF-based OLED. The device showed maximum external quantum efficiency of 15.1%. Another compound exhibiting efficient TADF demonstrated oxygen sensitivity with non-linear Stern-Volmer curve which was well fitted by two Stern-Volmer constants of 6.54·10−4 and 7.17·10−6 ppm−1.

Preparation of different morphologies cellulose nanocrystals from waste cotton fibers and its effect on PLLA/PDLA composites films

In this paper, the influence of nanocellulose with different aspect ratio on the performance of PLLA/PDLA was explicit through a quantity of test results. Three different aspect ratio nanocelluloses were chemically extracted from waste colored cotton fibers. After acetylated and adding to PLLA/PDLA solution, PLLA/PDLA (LD) composites films were prepared by solution casting method and their properties were investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), tensile testing, oxygen permeability and optical measurement. It was found that nanocellulose play a role as nucleating agent to promote crystallization and was also helpful to form the stereocomplexs crystallites. Wherein, the acetylated cellulose nanospheres (ACNS) had the most obvious effect on crystallinity enhancing. The best oxygen barrier performance of LD composites films was occurred after addition acetylated cellulose nanocrystals (ACNC). Fibrous acetylated cellulose nanofiber (ACNF) had the most influence on tensile property. Furthermore, addition of ACNS, ACNC and ACNF had hardly impact on transmittance and haze of films. It is of guiding significance for the preparation of PLA composite materials applied in different fields.

Особенности временной изменчивости содержания кислорода в зарослях Zostera marina Linnaeus, 1753 в бухте Воевода (Амурский залив, Японское море)

В настоящее время мелководные бассейны с лугами Zostera marina L. рассматривают в качестве поглотителей атмосферного углекислого газа, способных сдерживать увеличение его концентрации. Благодаря своей высокой продуктивности взморник выделяет в среду большое количество кислорода. Для установления особенностей проявления продукционной активности мелководных бассейнов, покрытых лугами Z. marina, на примере бухты Воевода (Амурский залив, Японское море) проведён мониторинг гидрологических и продукционных параметров с различными интервалами измерений. Наблюдения продолжались 8,5 мес. (22.09.2012–07.06.2013). В зарослях Z. marina на глубине 4 м измеряли температуру, солёность, флуоресценцию хлорофилла и мутность с помощью гидрологической станции Water Quality Monitor с интервалом 3 часа. Малоинерционным оптическим кислородным датчиком ARO-USB определяли концентрацию растворённого кислорода с интервалом 1 час. Установлено два типа изменчивости содержания кислорода в среде: 1) долгопериодная изменчивость, обусловленная сезонными изменениями среды; 2) суточная в период ледостава, определяемая интенсивностью проникновения фотосинтетически активной радиации в подлёдную воду. В осенний сезон отмечены низкие концентрации кислорода, достигающие уровня гипоксии. Для зимнего и весеннего периодов содержание кислорода находилось, как правило, на уровне 100–130 % от насыщения. Высокую суточную изменчивость наблюдали в период ледостава, в отсутствие снега. В феврале амплитуда суточных колебаний концентрации кислорода достигала 730 мкмоль·кг−1, с трёхкратным пересыщением по отношению к атмосферному O2. Установлено, что максимальная скорость продукции кислорода, отнесённая к 1 г сырой массы Z. marina, составляет 6,5 мг O2·час−1·г−1. Суточная динамика кислорода в морской воде проанализирована в связи с физиологическими особенностями Z. marina (воздухоносные полости в побегах играют важную роль в динамике кислорода в среде), а также в связи с короткопериодными приливами.

Automated Miniaturized Digital Microfluidic Antimicrobial Susceptibility Test Using a Chip-Integrated Optical Oxygen Sensor.

We present the first digital microfluidic (DMF) antimicrobial susceptibility test (AST) using an optical oxygen sensor film for in-situ and real-time continuous measurement of extracellular dissolved oxygen (DO). The device allows one to monitor bacterial growth across the entire cell culture area, and the fabricated device was utilized for a miniaturized and automated AST. The oxygen-sensitive probe platinum(II)-5,10,15,20-tetrakis-(2,3,4,5,6-pentafluorophenyl)-porphyrin was embedded in a Hyflon AD 60 polymer and spin-coated as a 100 nm thick layer onto an ITO glass serving as the DMF ground electrode. This DMF-integrated oxygen sensing film was found to cause no negative effects to the droplet manipulation or cell growth on the chip. The developed DMF platform was used to monitor the DO consumption during Escherichia coli(E. coli) growth caused by cellular respiration. A rapid and reliable twofold dilution procedure was developed and performed, and the AST with E. coli ATCC 25922 in the presence of ampicillin, chloramphenicol, and tetracycline at different concentrations from 0.5 to 8 μg mL-1 was investigated. All sample dispensation, dilution, and mixing were performed automatically on the chip within 10 min. The minimum inhibitory concentration values measured from the DMF chip were consistent with those from the standard broth microdilution method but requiring only minimal sample handling and working with much smaller sample volumes.

Viability determination of Bacillus sphaericus after encapsulation in hydrogel for self-healing concrete via microcalorimetry and in situ oxygen concentration measurements

Techniques for bacteria based self-healing concrete are currently limited to indirect bacterial activity measurements and visual crack closing effects after self-healing has occurred. In the present study, direct and reliable bacteria survival measurements after encapsulation in protective carriers were carried out by utilizing microcalorimetry analysis. After further incorporation in mortar oxygen consumption was determined by use of an optical oxygen sensing system. The microscope analysis showed that a 90% sporulation of Bacillus sphaericus was achieved after 24 h incubation. Microcalorimeter measurements detected the heat generation from microbial activity on the third day of incubation which provides direct evidence that bacteria can be activated after encapsulation inside the hydrogel. The application of the O2 sensing film on cracked mortar showed a high oxygen concentration reduction (66%) near the crack opening. This confirmed the activation of B. sphaericus and use of oxygen as an electron acceptor for their metabolism after incorporation inside mortar specimens.

Effects of surface structure and defect behavior on the magnetic, electrical, and photocatalytic properties of Gd-doped CeO2 nanoparticles synthesized by a simple chemical process

Magnetic, electrical, and photocatalytic characteristics of a series of nanoparticles (NPs) of Gd-doped CeO2 (GdxCe1-xO2 (100x% GDC); x = 0.03, 0.05, 0.10, and 0.20) were analyzed in correlation with their surface structure and defect behavior. The GDC NPs were synthesized by a simple chemical process through a polymer-based precursor. X-ray diffraction (XRD) studies confirmed the effective substitution of Gd3+ in the face centered cubic (fcc) lattice of the host matrix of CeO2. The optical band gap (Eg) and oxygen vacancies (VO) increased with Gd-doping as validated by UV–visible reflectance and Raman spectroscopy. Further analysis with X-ray photoelectron spectroscopy (XPS) substantiated the formation of non-stoichiometric CeO2 structure through Ce4+ → Ce3+ reduction to maintain charge neutrality after Gd-doping. Samples of 20% GDC processed at 400 °C, showed the highest saturation magnetization (MS) of 17.58 memu/g at room temperature. A maximum conductivity of 2.11 × 10−3 S/cm was recorded at 650 °C in air in the 20% GDC samples processed at 1100 °C. Using 20% GDC NPs processed at 400 °C, a typical value of apparent degradation rate constant (k) of 2.13 × 10−2 min−1 was obtained for methyl orange (MO) dye under UV–visible irradiation for 10 min.

Injectable, dispersible polysulfone-polysulfone core-shell particles for optical oxygen sensing.

Injectable sensors can significantly improve the volume of critical biomedical information emerging from the human body in response to injury or disease. Optical oxygen sensors with rapid response times can be achieved by incorporating oxygen-sensitive luminescent molecules within polymeric matrices with suitably high surface area to volume ratios. In this work, electrospraying utilizes these advances to produce conveniently injectable, oxygen sensing particles made up of a core-shell polysulfone-polysulfone structure containing a phosphorescent oxygen-sensitive palladium porphyrin species within the core. Particle morphology is highly dependent on solvent identity and electrospraying parameters; DMF offers the best potential for the creation of uniform, sub-micron particles. Total internal reflection fluorescence (TIRF) microscopy confirms the existence of both core-shell structure and oxygen sensitivity. The dissolved oxygen response time is rapid (<0.30 s), ideal for continuous real-time monitoring of oxygen concentration. The incorporation of Pluronic F-127 surfactant enables efficient dispersion; selection of an appropriate electrospraying solvent (DMF) yields particles readily injected even through a <100 μm diameter needle.

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.

Ultra-fast response polymer optical fiber oxygen measurement device and its preliminary experimental report on continuous dynamic change of arterial oxygen partial pressure under mechanical ventilation in living animals

Objective: We tried to implant the ultra-fast polymer optical fiber chemical oxygen sensor （POFCOS） into arterial blood vessel,connect with photoelectric conversion measurement system to record the continuous dynamic rapid changes of arterial PO2(PaO2) in whole living animals. It should be the experimental evidence for the new theory of holistic integrative physiology and medicine(HIPM) forexplain the mechanism of respiratory control and regulation in whole circusof respiration-circulation-metabolism. Methods: ①Fabrication of ultrafast POFCOS, calibration and its measuring system: The distal part of 2 m optical fiber was heated and pulled until it became a tapered tip. After cleaning and drying, the tip of 1 mm tapered optical fiber was dip-coated into the luminophore doped polymer solution, then was slowly pumped out while solvent was quickly evaporated to form an oxygen sensing tip, which was dried at room temperature for 24 hours. ②Animal experiments: Under general anesthesia and intubation, goatwas mechanically ventilated with 40%~60% oxygen. We exposed both right and left carotid arteries and the left femoral artery by skin cutting, and inserted the POFCOS directly into the arteries via indwelling catheter. The end of POFCOS were connected to the personal computer through optical fiber, excitation and detection Y-type optical fiber coupler through photoelectric conversion, so as we can realize the continuous dynamic response of living goat carotid PaO2 under mechanical ventilation. We mainly analyzed the intra-breath wave-form alternate increase and decrease of PaO2 and their time delay between lung and carotid arteries.We completes breathing control whole loop to explain the mechanism of mutual breathing and the switching of inspiration and exhalation. Results: The POFCOS has a very fast T90 response time was set 100 ms for liquid. When the heart rate of 40%~60% oxygen mechanical ventilated living goat was ~110 bpm, the PaO2 of left and right carotid artery showed a same wave-sizeup and down following with the inspiration and expiration of ventilator, with a range of up to 15 mmHg. There weresignificant noises of PaO2 change recorded in the left femoral artery. The lung-carotid artery time delay is 1.5~1.7 s after inhalation and exhalation, PaO2 at both left and right carotid arteries starts toincrease and decrease. After two-three heartbeats after the start of lung ventilation, thealternate up-down wave-form information of the arterialized pulmonary vein blood after pulmonary capillaries waspumpedby left ventricle to the position of peripheral chemoreceptors,thus realizing the whole cycle of inhalation and exhalation. It alternately interrupted inhalation, i.e. switching inhalation to exhalation, and then interrupted exhalation,i.e. switching exhalation to inhalation. Conclusion: The ultra-fast reactive implantableoxygen sensor and its measuring system can measure the physiological waveform changes of PaO2 in living animals, which can provide experimental evidence for explaining the mechanism of switching of inspiration-expiration in HIPM.

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.

Developing a Wearable Sensor for Continuous Tissue Oxygenation Monitoring: A Proof of Concept Study

Abstract Objective Technologies facilitating continuous free tissue flap monitoring such as near infrared spectroscopy (NIRS) have been shown to improve flap salvage rates. However, the size and associated costs of such technology create a barrier to wider implementation. The aim of this study was to develop and validate a wearable sensor for continuous tissue oxygenation monitoring. Materials and Methods A forearm ischemia model was designed by using a brachial pressure cuff inflation protocol. Twenty healthy subjects were recruited. The forearm tissue oxygenation of each subject was monitored throughout the pressure cuff protocol by using a new optical sensor (Imperial College London), and a gold standard tissue spectrometry system (O2C, Medizintecknik, LEA, Germany). Data were processed to allow quantitative deoxygenation episode comparisons between inflations and sensor modalities. Results The correlation between O2C and optical sensor oxygenation measurements was moderate (average R = 0.672, p &lt; 0.001). Incremental increases in cuff inflation duration resulted in a linear increase in deoxygenation values with both O2C and optical sensors, with significant differences recorded on consecutive inflations (wall shear rate, p &lt; 0.005). The presence or absence of pulsatile blood flow was correctly determined throughout by both sensor modalities. Conclusion This study demonstrates the ability of a small optical sensor to detect and quantify tissue oxygenation changes and assess the presence of pulsatile blood flow. Low power, miniaturized electronics make the device capable of deployment in a wearable form which may break down the barriers for implementation in postoperative flap monitoring.

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.

Visible light induced selective photocatalytic reduction of CO2 to CH4 on In2O3-rGO nanocomposites

Maintaining the atmospheric CO2 by its utilization in the production of valuable solar fuel like methane is one of the major challenges for humankind. Photocatalytic reduction of CO2 is a vital approach for its consumption by conversion into a valuable chemical product. Here, we prepared In2O3-rGO nanocomposites with varying reduced graphene oxide (rGO) content for the investigation of photocatalytic reduction of CO2. The product yield obtained by photocatalytic reduction of CO2 by visible light source was quantified by exploring the gas chromatography measurements. The catalytic activity of In2O3-rGO nanocomposites towards the photocatalytic reduction process of CO2 to CH4 gets enhanced as compared to In2O3 nanostructures due to the enhancement of lifetime of separation of photogenerated electron-hole pairs, which assist in improvement of charge transfer from In2O3 to rGO under visible light source. The In2O32wt%rGO nanocomposite exhibits a maximum methane yield of 953.72 μmol.g−1. The highest catalytic performance of In2O3-2wt%rGO nanocomposite may be attributed to improvement in its optical properties such as optical band gap and oxygen vacancies (Vo) defects by the addition of rGO in it. A mechanism based on the oxygen vacancies mediated charge transfer process is invoked to explain the observed enhancement in the photocatalytic reduction of CO2.

Implantable sensor for local Cherenkov-excited luminescence imaging of tumor pO2 during radiotherapy.

.Significance: The necessity to use exogenous probes for optical oxygen measurements in radiotherapy poses challenges for clinical applications. Options for implantable probe biotechnology need to be improved to alleviate toxicity concerns in human use and facilitate translation to clinical trial use.Aim: To develop an implantable oxygen sensor containing a phosphorescent oxygen probe such that the overall administered dose of the probe would be below the Federal Drug Administration (FDA)-prescribed microdose level, and the sensor would provide local high-intensity signal for longitudinal measurements of tissue .Approach: PtG4, an oxygen quenched dendritic molecule, was mixed into an agarose matrix at concentration, allowing for local injection into tumors at the total dose of 10 nmol per animal, forming a gel at the site of injection. Cherenkov-excited luminescence imaging (CELI) was used to acquire the phosphorescence and provide intratumoral .Results: Although PtG4 does not form covalent bonds with agarose and gradually leaches out into the surrounding tissue, its retention time within the gel was sufficiently long to demonstrate the capability to measure intratumoral with the implantable gel sensors. The sensor’s performance was first evaluated in vitro in tissue simulation phantoms, and then the sensor was used to measure changes in oxygen in MDA-MB-231 tumors during hypofractionated radiotherapy.Conclusions: Our study demonstrates that implantable oxygen sensors in combination with CELI present a promising approach for quantifying oxygen changes during the course of radiation therapy and thus for evaluating the tumor response to radiation. By improving the design of the gel–probe composition in order to prevent leaching of the probe into the tissue, biosensors can be created that should allow longitudinal oxygen measurements in tumors by means of CELI while using FDA-compliant microdose levels of the probe and thus lowering toxicity concerns.