Chemosensors, Volume 4, Issue 2 (June 2016) – 5 articles

Protein analysis and quantification are required daily by thousands of laboratories worldwide for activities ranging from protein characterization to clinical diagnostics. Multiple factors have to be considered when selecting the best detection and quantification assay, including the amount of protein available, its concentration, the presence of interfering molecules, as well as costs and rapidity. This is also the case for lysozyme, a 14.3-kDa protein ubiquitously present in many organisms, that has been identified with a variety of functions: antibacterial activity, a biomarker of several serious medical conditions, a potential allergen in foods or a model of amyloid-type protein aggregation. Since the design of the first lysozyme aptamer in 2001, lysozyme became one of the most intensively-investigated biological target analytes for the design of novel biosensing concepts, particularly with regards to electrochemical aptasensors. In this review, we discuss the state of the art of aptamer-based electrochemical sensing of lysozyme, with emphasis on sensing in serum and real samples. Full article

Strontium-82 is produced by proton activation of a rubidium chloride target in an accelerator or cyclotron and purified by ion exchange chromatography. The Strontrium-82 is used in Cardigen generators to produce Rubidium-82 for cardiac imaging. Quality control testing of the purified Strontium-82 is performed with Inductively Coupled Plasma-Optical Emission spectroscopy (ICP-OES) and gamma spectroscopy. To meet Department of Energy specifications for HCl molarity the purified Strontium-82 solution needs to be tested to determine if the isotope is in the 0.05–0.5 M HCl range. This manuscript reports a simple HCl molarity test to determine if the purified Strontium-82 solution meets specifications. Validation of the assay was performed by evaluating all solutions associate with Strontium-82 processing. Full article

NO₂ emission is mostly related to combustion processes, where gas temperatures exceed far beyond 500 °C. The detection of NO₂ in combustion and exhaust gases at elevated temperatures requires sensors with high NO₂ selectivity. The thermodynamic equilibrium for NO₂/NO ≥ 500 °C lies on the NO side. High temperature stability of TiO₂ makes it a promising material for elevated temperature towards CO, H₂, and NO₂. The doping of TiO₂ with Al³⁺ (Al:TiO₂) increases the sensitivity and selectivity of sensors to NO₂ and results in a relatively low cross-sensitivity towards CO. The results indicate that NO₂ exposure results in a resistance decrease of the sensors with the single Al:TiO₂ layers at 600 °C, with a resistance increase at 800 °C. This alteration in the sensor response in the temperature range of 600 °C and 800 °C may be due to the mentioned thermodynamic equilibrium changes between NO and NO₂. This work investigates the NO₂-sensing behavior of duplex layers consisting of Al:TiO₂ and BaTi_(1-x)Rh_xO₃ catalysts in the temperature range of 600 °C and 900 °C. Al:TiO₂ layers were deposited by reactive magnetron sputtering on interdigitated sensor platforms, while a catalytic layer, which was synthesized by wet chemistry in the form of BaTi_(1-x)Rh_xO₃ powders, were screen-printed as thick layers on the Al:TiO₂-layers. The use of Rh-incorporated BaTiO₃ perovskite (BaTi_(1-x)Rh_xO₃) as a catalytic filter stabilizes the sensor response of Al-doped TiO₂ layers yielding more reliable sensor signal throughout the temperature range. Full article

The development of an electrochemical dissolved oxygen (DO) sensor based on a novel Cu(II) complex-modified screen printed carbon electrode is reported. The voltammetric behavior of the modified electrode was investigated at different scan rates and oxygen concentrations in PBS (pH = 7). An increase of cathodic current (at about −0.4 vs. Ag/AgCl) with the addition of oxygen was observed. The modified Cu(II) complex electrode was demonstrated for the determination of DO in water using chronoamperometry. A small size and low power consumption home-made portable electrochemical analyzer based on custom electronics for sensor interfacing and operating in voltammetry and amperometry modes has been also designed and fabricated. Its performances in the monitoring of DO in water were compared with a commercial one. Full article

One-dimensional metal oxide nanostructures such as nanowires, nanorods, nanotubes, and nanobelts gained great attention for applications in sensing devices. ZnO is one of the most studied oxides for sensing applications due to its unique physical and chemical properties. In this paper, we provide a review of the recent research activities focused on the synthesis and sensing properties of pure, doped, and functionalized ZnO quasi-one dimensional nanostructures. We describe the development prospects in the preparation methods and modifications of the surface structure of ZnO, and discuss its sensing mechanism. Next, we analyze the sensing properties of ZnO quasi-one dimensional nanostructures, and summarize perspectives concerning future research on their synthesis and applications in conductometric sensing devices. Full article