In-Situ Gold–Ceria Nanoparticles: Superior Optical Fluorescence Quenching Sensor for Dissolved Oxygen

Cerium oxide (ceria) nanoparticles (NPs) have been proved to be an efficient optical fluorescent material through generating visible emission (~530 nm) under violet excitation. This feature allowed ceria NPs to be used as an optical sensor via the fluorescence quenching Technique. In this paper, the impact of in-situ embedded gold nanoparticles (Au NPs) inside ceria nanoparticles was studied. Then, gold–ceria NPs were used for sensing dissolved oxygen (DO) in aqueous media. It was observed that both fluorescence intensity and lifetime were changed due to increased concentration of DO. Added gold was found to enhance the sensitivity of ceria to DO quencher detection. This enhancement was due to optical coupling between the fluorescence emission spectrum of ceria with the surface plasmonic resonance of gold nanoparticles. In addition, gold caused the decrease of ceria nanoparticles’ bandgap, which indicates the formation of more oxygen vacancies inside the non-stoichiometric crystalline structure of ceria. The Stern–Volmer constant, which indicates the sensitivity of optical sensing material, of ceria–gold NPs with added DO was found to be 893.7 M−1, compared to 184.6 M−1 to in case of ceria nanoparticles only, which indicates a superior optical sensitivity to DO compared to other optical sensing materials used in the literature to detect DO. Moreover, the fluorescence lifetime was found to be changed according to the variation of added DO concentration. The optically-sensitivity-enhanced ceria nanoparticles due to embedded gold nanoparticles can be a promising sensing host for dissolved oxygen in a wide variety of applications including biomedicine and water quality monitoring

A Dissolved Oxygen Measurement Based on Fiber Optical Oxygen Sensor

For the determination of dissolved oxygen, working principle of the fiber optic oxygen sensor is studied. The sensor system calibration method and temperature compensation measures and their maintenance methods are analyzed. The dissolved oxygen sensors current widely using oxygen electrode and optical fiber oxygen sensor are compared. Optical fiber probe sensor is used in the current system, the multiple points and multiple samples can achieve the simultaneous detection

Nanoparticle-based intra-cellular diagnostics

An in-depth understanding of biochemical processes occurring within the cell is a key factor for early diagnosis of disease and identification of appropriate treatment. Intracellular sensing using fluorescent nanoparticles (NPs) is a potentially useful tool for real-time, in vivo monitoring of important cellular analytes. This work is focused on synthesis of organically modified-silicate (ORMOSIL) optical nanosensors for the quantitative analysis of oxygen concentration and pH sensing inside the cell. The structure of the sensor consists of a biofriendly silica matrix with encapsulated oxygen/pH-sensitive dyes. The optical probes used in this work are the oxygen-sensitive ([Ru(dpp)3]2+) complex and pH-sensitive fluorescein isothiocyanate (FITC) coencapsulated with the ATTO488 and Texas Red as the reference dyes, respectively. In order to obtain silica-based NPs, the Stöber method was used. The NPs were characterised using techniques such as Transmission Electron Microscopy (TEM), Dynamic Light Scattering (DLS), fluorescence and other spectroscopic techniques. The second part of this work focuses on the introduction of the NPs into the cell and intracellular sensing. In this work the oxygen and pH nanosensors are introduced in a number of established human and mouse cell lines. Internalization of NPs within the cell is investigated using fluorescence confocal microscopy techniques. The detection of the optical signal is based on both ratiometric and fluorescence lifetime – based measurements carried out on the wide-field and confocal microscopes with fluorescence lifetime imaging platforms. After the NP calibration, the response of the cell to the different extracellular oxygen concentration is investigated. Oxygen and pH sensing is the starting point for this intracellular diagnostics research. The silica-based NPs, thanks to the flexible processing conditions, allow for tailoring of pore size and hydrophilic-hydrophobic balance. The possibility to control these two parameters makes the NPs a very promising tool for a better understanding of many processes in living cells

The Challenges of O2 Detection in Biological Fluids: Classical Methods and Translation to Clinical Applications

Dissolved oxygen (DO) is deeply involved in preserving the life of cellular tissues and human beings due to its key role in cellular metabolism: its alterations may reflect important pathophysiological conditions. DO levels are measured to identify pathological conditions, explain pathophysiological mechanisms, and monitor the efficacy of therapeutic approaches. This is particularly relevant when the measurements are performed in vivo but also in contexts where a variety of biological and synthetic media are used, such as ex vivo organ perfusion. A reliable measurement of medium oxygenation ensures a high-quality process. It is crucial to provide a high-accuracy, real-time method for DO quantification, which could be robust towards different medium compositions and temperatures. In fact, biological fluids and synthetic clinical fluids represent a challenging environment where DO interacts with various compounds and can change continuously and dynamically, and further precaution is needed to obtain reliable results. This study aims to present and discuss the main oxygen detection and quantification methods, focusing on the technical needs for their translation to clinical practice. Firstly, we resumed all the main methodologies and advancements concerning dissolved oxygen determination. After identifying the main groups of all the available techniques for DO sensing based on their mechanisms and applicability, we focused on transferring the most promising approaches to a clinical in vivo/ex vivo settin

Classification of analytics, sensorics, and bioanalytics with polyelectrolyte multilayer capsules

Polyelectrolyte multilayer (PEM) capsules, constructed by LbL (layer-by-layer)-adsorbing polymers on sacrificial templates, have become important carriers due to multifunctionality of materials adsorbed on their surface or encapsulated into their interior. They have been also been used broadly used as analytical tools. Chronologically and traditionally, chemical analytics has been developed first, which has long been synonymous with all analytics. But it is not the only development. To the best of our knowledge, a summary of all advances including their classification is not available to date. Here, we classify analytics, sensorics, and biosensorics functionalities implemented with polyelectrolyte multilayer capsules and coated particles according to the respective stimuli and application areas. In this classification, three distinct categories are identified: (I) chemical analytics (pH; K+, Na+, and Pb2+ ion; oxygen; and hydrogen peroxide sensors and chemical sensing with surface-enhanced Raman scattering (SERS)); (II) physical sensorics (temperature, mechanical properties and forces, and osmotic pressure); and (III) biosensorics and bioanalytics (fluorescence, glucose, urea, and protease biosensing and theranostics). In addition to this classification, we discuss also principles of detection using the above-mentioned stimuli. These application areas are expected to grow further, but the classification provided here should help (a) to realize the wealth of already available analytical and bioanalytical tools developed with capsules using inputs of chemical, physical, and biological stimuli and (b) to position future developments in their respective fields according to employed stimuli and application areas

Molecular probes: an innovative technology for monitoring membrane processes

The ultimate objective of this study is to use molecular probes as an innovative and alternative technology contributing to the advance of membrane science by monitoring membrane processes in-situ, on-line and at sub-micron scale. An optical sensor for oxygen sensing was developed by the immobilization of tris (1, 10-phenanthroline) ruthenium (II) (Ru(phen)3) in a dense polymeric membrane made of polystyrene (PS) or Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). The emission of the probe was quenched by both the temperature and by the oxygen. Moreover, the oxygen sensitivity was affected by the oxygen permeability of the membrane. The evaluation of the oxygen concentration is prone to errors since the emission of a single probe depends on several parameters (i.e. optical path, source intensity). The correction of these artefacts was obtained by the immobilization of a second luminescent molecule non-sensitive to the oxygen, Coumarin. The potential of the luminescent ratiometric sensor for the non-invasive monitoring of oxygen in food packaging using polymeric films with different oxygen permeability was evaluated. Emphasis was given to the efficiency of the optical sensor for the on-line, in-situ and non invasive monitoring of the oxygen by comparing the experimental data with a model which takes into account the oxygen permeability of the packaging materials evaluated independently. A nano-thermometer based on silica nano-particles doped with Ru(phen)3 was developed. A systematic study shows how it is possible to control the properties of the nano-particles as well as their temperature sensitivity. The nano-thermometer was immobilized on a membrane surface by dip-coating providing information about the temperature on the membrane surface. Hydrophobic porous membrane made of Poly(vinylidene fluoride) was prepared via electrospinning and employed in a direct contact membrane distillation process. Using a designed membrane module and a membrane doped with Ru(phen)3 the on-line mapping of the temperature on the membrane’s surface was evaluated

Carbon dioxide sensors for food packaging

Traditional food packaging objective is the isolation of products from the outer atmosphere to extend their shelf life. In response to current necessities, traditional food packaging has led to smart packaging. CO2 inside food packages is a key factor to control. CO2 sensors can give information about the modified atmosphere integrity, indicating that the inner atmosphere is intact or if it has been broken and therefore the used by date must not be trusted, or about how fresh is the packaged product. This article briefly describes the types of packaging (traditional and smart) and how CO2 sensors can be used in the food industry. Different approaches for their integration in packaged food are described and the characteristics that must comply in order to be integrated in the agro-alimentary industry.European Union's Horizon 2020 research and innovation programme under grant agreement No 706303 (Multisens)CTQ2016–78754-C2-1-R project from the Spanish MINECO