Photophysical Details and O2-Sensing Analysis of a Eu(III) Complex in Polymer Composite Nanofibers Prepared by Electrospinning

An as-synthesized Eu(III) complex, denoted as Eu(N-DPNQ)(TTD)3, was prepared and characterized, and the antenna mechanism between these ligands and central metal emitter was studied. Here DPNQ means 10-ethyl-10H-indolo [2′,3':5,6]pyrazino[2,3-f][1,10]phenanthroline and TTD is 4,4,4-trifluoro-1-(thiophen-2-yl)butane-1,3-dione. We find that Eu(N-DPNQ)(TTD)3 emission intensity dependents on oxygen concentration, and O2-sensing skill of Eu(N-DPNQ)(TTD)3 in polymer composite nanofibers of poly (vinylpyrrolidone) (PVP) prepared by electrospinning is investigated. Results reveal that the emission quenching of Eu(N-DPNQ)(TTD)3 is caused by the ground state (triplet) oxygen quenching on antenna ligands triplet state. The Eu(N-DPNQ)(TTD)3 doped composite nanofiber with a loading level of 6 wt% exhibits the best result with sensitivity of 2.43 and response time of 10 s, along with linear response.

Microfluidic-Based Oxygen (O2) Sensors for On-Chip Monitoring of Cell, Tissue and Organ Metabolism

Oxygen (O2) quantification is essential for assessing cell metabolism, and its consumption in cell culture is an important indicator of cell viability. Recent advances in microfluidics have made O2 sensing a crucial feature for organ-on-chip (OOC) devices for various biomedical applications. OOC O2 sensors can be categorized, based on their transducer type, into two main groups, optical and electrochemical. In this review, we provide an overview of on-chip O2 sensors integrated with the OOC devices and evaluate their advantages and disadvantages. Recent innovations in optical O2 sensors integrated with OOCs are discussed in four main categories: (i) basic luminescence-based sensors; (ii) microparticle-based sensors; (iii) nano-enabled sensors; and (iv) commercial probes and portable devices. Furthermore, we discuss recent advancements in electrochemical sensors in five main categories: (i) novel configurations in Clark-type sensors; (ii) novel materials (e.g., polymers, O2 scavenging and passivation materials); (iii) nano-enabled electrochemical sensors; (iv) novel designs and fabrication techniques; and (v) commercial and portable electrochemical readouts. Together, this review provides a comprehensive overview of the current advances in the design, fabrication and application of optical and electrochemical O2 sensors.

Mitochondrial Succinate Metabolism and Reactive Oxygen Species Are Important but Not Essential for Eliciting Carotid Body and Ventilatory Responses to Hypoxia in the Rat

Reflex increases in breathing in response to acute hypoxia are dependent on activation of the carotid body (CB)—A specialised peripheral chemoreceptor. Central to CB O2-sensing is their unique mitochondria but the link between mitochondrial inhibition and cellular stimulation is unresolved. The objective of this study was to evaluate if ex vivo intact CB nerve activity and in vivo whole body ventilatory responses to hypoxia were modified by alterations in succinate metabolism and mitochondrial ROS (mitoROS) generation in the rat. Application of diethyl succinate (DESucc) caused concentration-dependent increases in chemoafferent frequency measuring approximately 10–30% of that induced by severe hypoxia. Inhibition of mitochondrial succinate metabolism by dimethyl malonate (DMM) evoked basal excitation and attenuated the rise in chemoafferent activity in hypoxia. However, approximately 50% of the response to hypoxia was preserved. MitoTEMPO (MitoT) and 10-(6′-plastoquinonyl) decyltriphenylphosphonium (SKQ1) (mitochondrial antioxidants) decreased chemoafferent activity in hypoxia by approximately 20–50%. In awake animals, MitoT and SKQ1 attenuated the rise in respiratory frequency during hypoxia, and SKQ1 also significantly blunted the overall hypoxic ventilatory response (HVR) by approximately 20%. Thus, whilst the data support a role for succinate and mitoROS in CB and whole body O2-sensing in the rat, they are not the sole mediators. Treatment of the CB with mitochondrial selective antioxidants may offer a new approach for treating CB-related cardiovascular–respiratory disorders.

Efficient N2- and O2-Sensing Properties of PtSe2 With Proper Intrinsic Defects

Developing efficient N2 and O2 gas sensors is of great importance to our daily life and industrial technology. In this work, first-principles calculations are performed to study the N2 and O2 gas-sensing properties of pure and defected PtSe2. It is found that both N2 and O2 adsorb weakly on pure PtSe2, and adsorption of the molecules induces negligible changes in the electrical and optical properties. Whereas the Pt@Se anti-site defect significantly improves the N2 adsorption capacity of PtSe2 and induces notable changes in the electrical property. Similar results are also observed for the Pt and Se vacancies and Pt@Se anti-site defects when examining O2 adsorption. In addition, notable changes in the optical absorption spectra of the PtSe2 with Pt@Se defect are induced upon N2 adsorption, which also occurs for PtSe2 with Pt and Se vacancies and Pt@Se anti-site defects upon O2 adsorption. These results demonstrate that PtSe2 with the corresponding defects can be both excellent electrical and optical sensors for detecting N2 and O2 gases. Our work offers a new avenue for preparing efficient gas sensors.

The Oxidative Paradox in Low Oxygen Stress in Plants

Reactive oxygen species (ROS) are part of aerobic environments, and variations in the availability of oxygen (O2) in the environment can lead to altered ROS levels. In plants, the O2 sensing machinery guides the molecular response to low O2, regulating a subset of genes involved in metabolic adaptations to hypoxia, including proteins involved in ROS homeostasis and acclimation. In addition, nitric oxide (NO) participates in signaling events that modulate the low O2 stress response. In this review, we summarize recent findings that highlight the roles of ROS and NO under environmentally or developmentally defined low O2 conditions. We conclude that ROS and NO are emerging regulators during low O2 signalling and key molecules in plant adaptation to flooding conditions.

OXYGEN-DEPENDENT ADAPTATION PROCESSES IN THE HUMAN ORGANISM IN USUAL LIVING CONDITIONS AND DURING SPACE FLIGHT

The review examines various parties of oxygen-dependent human adaptation to microgravity belonging to different levels of the integral system organization. Particular emphasis has been placed on the cellular sensing systems of immediate and chronic reactions to altered O2 delivery. The authors expound the key oxygen sensors and heterogeneity of the sensing mechanisms. They also concern themselves with the role of O2 active forms and O2-sensing elements developing in the spaceflight environment. The first post-flight evidence of an increase in frequency of oxidation post-translational modifications in proteins suggests a hypothesis about the direction and systemic mechanisms of oxygen-dependent adaptation of the human organism to in microgravity.

The hypoxia-reoxygenation stress in plants

Plants are very plastic in adapting growth and development to changing adverse environmental conditions. This feature will be essential for plants to survive climate changes characterized by extreme temperatures and rainfall. Although plants require molecular oxygen (O2) to live, they can overcome transient low O2 conditions (hypoxia) until return to standard 21% O2 atmospheric conditions (normoxia). After heavy rainfall, submerged plants in flooded lands undergo transient hypoxia until water recedes and normoxia is recovered. The accumulated information on the physiological and molecular events occurring during the hypoxia phase contrasts with the limited knowledge on the reoxygenation process after hypoxia, which has been often overlooked in many studies in plants. Phenotypic alterations during recovery are due to potentiated oxidative stress generated by simultaneous reoxygenation and reillumination leading to cell damage. Besides processes like N-degron proteolytic pathway-mediated O2 sensing, or mitochondria-driven metabolic alterations, other molecular events controlling gene expression have been recently proposed as key regulators of hypoxia and reoxygenation. RNA regulatory functions, chromatin remodeling, protein synthesis and post-translational modifications must all be deeply studied in the next years to improve our knowledge on hypoxia-reoxygenation transition in plants, a topic with relevance in agricultural biotechnology in the context of global climate change.