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We report on the fabrication and characterization of single-crystal Gallium Nitride (GaN) membrane organic gas sensor. The sensing device is based on the highly stable free-standing III-nitride membrane, and it is probed using non-destructive impedance spectroscopy. Monitoring the effect of a series of polar organic molecules on the electrochemical impedance spectrum of the sensing membrane in the frequency range of 1 mHz to 0.1 MHz at room temperature, we concluded that the sensor is highly sensitive to alcohols, in the gas phase, with selectivity that depends on the molecular weight and vapor pressure of the molecules. The highly robust and stable GaN crystalline membrane and the ability to test these sensors using impedance spectroscopy and electrochemical probing techniques suggest that single crystal GaN-based sensors can find a wide range of applications in harsh and extreme environments. [ABSTRACT FROM AUTHOR]

Abstract: Effective immobilization of biomolecules at transducer interfaces plays a crucial role in biosensors development. In this work, we compared several silicon nitride (Si3N4) surface silanization methods in terms of efficient biomolecule immobilization either through physical adsorption or covalent binding. Two silanizing agents, namely 3- aminopropyltriethoxysilane (APTES) and 3-glycidyloxypropyltrimethoxysilane (GOPTS), were employed. It was found that silanization with GOPTS provided slightly higher protein immobilization capacity and homogeneity and lower non-specific binding as compared to APTES modification. Therefore, it could be employed for the effective functionalization of Si3N4 waveguides for biosensing applications. [Copyright &y& Elsevier]

In 1962, during a rescue excavation at the cave site ‘tis Ouranias to Froudi’, near Zakros in eastern Crete, Professor N. Platon’s team detected and collected a substantial quantity of sea–salt dating to the Minoan Bronze Age. This salt has recently been analysed chemically and studied. It is a rare, if not unique, find that helps us to explore aspects of the archaeology of salt collection, storage and usage, as well as the position of the product within the circulation of primary goods. It also points to the need for research on salt not only as an essential preservative and condiment, but also as a material of specialized craft production. Here we shall try to combine physical and archaeological evidence, with the aim of achieving a better understanding of the cultural meanings of this second millennium BC salt. [ABSTRACT FROM AUTHOR]

The response of AlGaN/GaN electrolyte-gate high-electron-mobility transistors to various concentrations of the potassium salts KCl, KBr, KNO3, and KSCN in an aqueous solution has been investigated. The transistors’ drain-source current decreased with increasing concentration of potassium salts. This indicates that the potential at the gate becomes more negative with respect to the channels’ potential, suggesting a selective anion adsorption onto the GaN gate surface area. [ABSTRACT FROM AUTHOR]

The endocannabinoid system (ECS) is a new target for the development of retinal disease therapeutics, whose pathophysiology involves neurodegeneration and neuroinflammation. The endocannabinoid 2-arachidonoylglycerol (2-AG) affects neurons and microglia by activating CB1/CB2 cannabinoid receptors (Rs). The aim of this study was to investigate the effects of 2-AG on the CB1R expression/downregulation and retinal neurons/reactive microglia, when administered repeatedly (4 d), in three different paradigms. These involved the 2-AG exogenous administration (a) intraperitoneally (i.p.) and (b) topically and (c) by enhancing the 2-AG endogenous levels via the inhibition (AM11920, i.p.) of its metabolic enzymes (MAGL/ABHD6). Sprague Dawley rats were treated as mentioned above in the presence or absence of CB1/CB2R antagonists and the excitatory amino acid, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA). Immunohistochemistry, Western blot and a 2-AG level analyses were performed. The 2-AG repeated treatment (i.p.) induced the CB1R downregulation, abolishing its neuroprotective actions. However, 2-AG attenuated the AMPA-induced activation of microglia via the CB2R, as concurred by the AM630 antagonist effect. Topically administered 2-AG was efficacious as a neuroprotectant/antiapoptotic and anti-inflammatory agent. AM11920 increased the 2-AG levels providing neuroprotection against excitotoxicity and reduced microglial activation without affecting the CB1R expression. Our findings show that 2-AG, in the three paradigms studied, displays differential pharmacological profiles in terms of the downregulation of the CB1R and neuroprotection. All treatments, however, attenuated the activation of microglia via the CB2R activation, supporting the anti-inflammatory role of 2-AG in the retina.

Pseudomonas sp. phDV1 is a polyhydroxyalkanoate (PHA) producer. The presence of the endogenous PHA depolymerase (phaZ) responsible for the degradation of the intracellular PHA is one of the main shortages in the bacterial production of PHA. Further, the production of PHA can be affected by the regulatory protein phaR, which is important in accumulating different PHA-associated proteins. PHA depolymerase phaZ and phaR knockout mutants of Pseudomonas sp. phDV1 were successfully constructed. We investigate the PHA production from 4.25 mM phenol and grape pomace of the mutants and the wild type. The production was screened by fluorescence microscopy, and the PHA production was quantified by HPLC chromatography. The PHA is composed of Polydroxybutyrate (PHB), as confirmed by 1 H-nuclear magnetic resonance analysis. The wildtype strain produces approximately 280 μg PHB after 48 h in grape pomace, while the phaZ knockout mutant produces 310 μg PHB after 72 h in the presence of phenol per gram of cells, respectively. The ability of the phaZ mutant to synthesize high levels of PHB in the presence of monocyclic aromatic compounds may open the possibility of reducing the costs of industrial PHB production.

Technological applications involving 2D MoS 2 require transfer of chemical vapor deposition (CVD) grown material from its original substrate and subsequent lithographic processes. Inevitably, those steps contaminate the surface of the 2D material with polymeric residues affecting the electronic and optical properties of the MoS 2 . Annealing in forming gas is considered an efficient treatment to partially remove such residues. However, hydrogen also interacts with MoS 2 creating or saturating sulfur vacancies. Sulfur vacancies are known to be at the origin of n-doping evident in the majority of as-grown MoS 2 samples. In this context, investigating the impact of thermal annealing in forming gas on the electronic and optical properties of MoS 2 monolayer is technologically important. In order to address this topic, we have systematically studied the evolution of CVD grown MoS 2 monolayer using Raman spectroscopy, photoluminescence, x-ray photoelectron spectroscopy and transport measurements through a series of thermal annealing in forming gas at temperatures up to 500 °C. Efficient removal of the polymeric residues is demonstrated at temperatures as low as 200 °C. Above this value, carrier density modulation is identified by photoluminescence, x-ray photoelectron spectroscopy and electrical characterization and is correlated to the creation of sulfur vacancies. Finally, the degradation of the MoS 2 single layer is verified with annealing at or above 350 °C through Raman and photocurrent measurements., (© 2020 IOP Publishing Ltd.)

Aggression plays a crucial role in survival all across the animal kingdom. In this study, we investigate the aggressive behaviour of Drosophila suzukii, a known agricultural pest. Bioassays were performed between same sex pairs and the effect of environmental (food deprivation, sex, age and photophase) and social factors (non-social and social). Initially the inter-male and inter-female aggression was determined ethologically consisting of several behaviour patterns. Two hours starvation period increase locomotor activity of flies, promoting increased aggressive behaviour. Most of the behavioural patterns were common between males and females with a few sex-selective. Number of male encounters was higher in flies held in isolation than in those that had been reared with siblings whereas in case of females, only those that were isolated exhibited increased aggression. Females and males D. suzukii that were 4-day-old were more aggressive. In addition it is found that on the 3 rd hour after the beginning of photophase, regardless of age, both males and females rise to high intensity aggression patterns.

An immunosensor for fast and accurate determination of C-reactive protein (CRP) in human serum samples based on an array of all-silicon broad-band Mach-Zehnder interferometers (BB-MZIs) is demonstrated. The detection was based on monitoring the spectral shifts during the binding of CRP on the antibody molecules that have been immobilized on the sensing arms of the BB-MZIs. By employing the reaction rate as the analytical signal the assay time was compressed to few minutes. The detection limit was 2.1ng/mL, the quantification limit was 4.2ng/mL and the linear dynamic range extended up to 100ng/mL. The measurements performed in human serum samples with the developed immunosensor were characterized by high repeatability and accuracy as it was demonstrated by dilution linearity and recovery experiments. In addition, the concentration values determined were in excellent agreement with those determined for the same samples by a standard clinical laboratory method. The compact size of the chip makes the proposed immunosensor attractive for incorporation into miniaturized devices for the determination of clinical analytes at the point-of-need., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Hydrogen is a highly promising energy source with important social and economic implications. The ability of green algae to produce photosynthetic hydrogen under anaerobic conditions has been known for years. However, until today the yield of production has been very low, limiting an industrial scale use. In the present paper, 73 years after the first report on H(2)-production from green algae, we present a combinational biological system where the biodegradation procedure of one meta-substituted dichlorophenol (m-dcp) is the key element for maintaining continuous and high rate H(2)-production (>100 times higher than previously reported) in chloroplasts and mitochondria of the green alga Scenedesmus obliquus. In particular, we report that reduced m-dcps (biodegradation intermediates) mimic endogenous electron and proton carriers in chloroplasts and mitochondria, inhibit Photosystem II (PSII) activity (and therefore O(2) production) and enhance Photosystem I (PSI) and hydrogenase activity. In addition, we show that there are some indications for hydrogen production from sources other than chloroplasts in Scenedesmus obliquus. The regulation of these multistage and highly evolved redox pathways leads to high yields of hydrogen production and paves the way for an efficient application to industrial scale use, utilizing simple energy sources and one meta-substituted dichlorophenol as regulating elements.

We demonstrate fabrication of microbiosensors utilizing a simple, rapid biomimetic silicification method catalyzed by poly-L-lysine at ambient temperature to provide a mild and efficient method for entrapment of the enzymes required for a range of analytes. To obtain a robust poly-L-lysine layer for precipitating silica onto the Pt surface, a Pt microelectrode was first functionalized with abundant carboxyl groups by electrochemical deposition of poly(pyrrole-1-propanoic acid). By means of zero length cross-linking reagents N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysulfosuccinimide sodium salt (NHSS), poly-L-lysine was covalently immobilized onto microelectrode surface. Under mild chemical conditions, three enzymes including adenosine deaminase (AD, EC 3.5.4.4), nucleoside phosphorylase (NP, EC 2.4.2.1) and xanthine oxidase (XO, EC 1.1.3.22) could then be simultaneously entrapped into a continuous silicate layer formed on top of Pt microelectrode from a mixture of enzymes and hydrolyzed silanes in Tris buffer (0.1M, pH 7.2) via the catalytic action of the attached poly-L-lysine. The fabricated adenosine biosensors exhibited good analytical performance with a sensitivity of 153.0+/-2.4 microA mM(-1)cm(-2) (n=4, R.S.D.=2.1%), a lower detection limit of 40 nM and a favourable response time (estimated as 10-90% response rise time) of 25+/-2s (n=4). The good selectivity of the adenosine microbiosensor against coexisting interfering substances such as ascorbic acid, urate and 5-HT was achieved through formation of a screening barrier from electrodeposited poly(diaminobenzene) following the biomimetic deposition process. We found that our methods were adaptable for other enzymes and analytes allowing fabrication of l-glutamate and lactate biosensors., (Copyright (c) 2010 Elsevier B.V. All rights reserved.)

SMARTDIAB is a platform designed to support the monitoring, management, and treatment of patients with type 1 diabetes mellitus (T1DM), by combining state-of-the-art approaches in the fields of database (DB) technologies, communications, simulation algorithms, and data mining. SMARTDIAB consists mainly of two units: 1) the patient unit (PU); and 2) the patient management unit (PMU), which communicate with each other for data exchange. The PMU can be accessed by the PU through the internet using devices, such as PCs/laptops with direct internet access or mobile phones via a Wi-Fi/General Packet Radio Service access network. The PU consists of an insulin pump for subcutaneous insulin infusion to the patient and a continuous glucose measurement system. The aforementioned devices running a user-friendly application gather patient's related information and transmit it to the PMU. The PMU consists of a diabetes data management system (DDMS), a decision support system (DSS) that provides risk assessment for long-term diabetes complications, and an insulin infusion advisory system (IIAS), which reside on a Web server. The DDMS can be accessed from both medical personnel and patients, with appropriate security access rights and front-end interfaces. The DDMS, apart from being used for data storage/retrieval, provides also advanced tools for the intelligent processing of the patient's data, supporting the physician in decision making, regarding the patient's treatment. The IIAS is used to close the loop between the insulin pump and the continuous glucose monitoring system, by providing the pump with the appropriate insulin infusion rate in order to keep the patient's glucose levels within predefined limits. The pilot version of the SMARTDIAB has already been implemented, while the platform's evaluation in clinical environment is being in progress.

Quantum dots (QDs) are inorganic semiconductor nanocrystals that have unique optoelectronic properties responsible for bringing together multidisciplinary research to impel their potential bioanalytical applications. In recent years, the many remarkable optical properties of QDs have been combined with the ability to make them increasingly biocompatible and specific to the target. With this great development, QDs hold particular promise as the next generation of fluorescent probes. This review describes the developments in functionalizing QDs making use of different bioconjugation and capping approaches. The progress offered by QDs is evidenced by examples on QD-based biosensing, biolabeling, and delivery of therapeutic agents. In the near future, QD technology still faces some challenges towards the envisioned broad bioanalytical purposes.

The properties of native and oxidised graphene layered carbon nanofibres are compared, and their utilisation in enzyme biosensor systems using different immobilisation methods are evaluated. The efficient oxidation of carbon nanofibres with concentrated H(2)SO(4)/HNO(3) is confirmed by Raman spectroscopy while the introduction of carboxylic acid groups on the surface of the fibres by titration studies. The oxidised fibres show enhanced oxidation efficiency to hydrogen peroxide, while at the same time they exhibit a more efficient and selective interaction with enzymes. The analytical characteristics of biosensor systems based on the adsorption or covalent immobilisation of the enzyme glucose oxidase on carbon nanofibres are compared. The study reveals that carbon nanofibres are excellent substrates for enzyme immobilisation allowing the development of highly stable biosensor systems.

Quantum dots are nanometre-scale semiconductor crystals with unique optical properties that are advantageous for the development of novel chemical sensors and biosensors. The surface chemistry of luminescent quantum dots has encouraged the development of multiple probes based on linked recognition molecules such as peptides, nucleic acids or small-molecule ligands. This review overviews the design of sensitive and selective nanoprobes, ranging from the type of target molecules to the optical transduction scheme. Representative examples of quantum dot-based optical sensors from this fast-moving field have been selected and are discussed towards the most promising directions for future research.