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Considering the increasing need for sensing elements that is emerging in different fields and applications, particularly in relation to the Internet of Things, electrochemical sensors and biosensors, also for their exceptional attributes, such as being easy-to-operate, economical, sensitive, portable, are candidates to become essential pillars in future scenarios and to play a significant role biomedical and environmental monitoring. Electrochemical and electrochemiluminescent sensors, are devices capable of detecting molecules and biomolecules in solutions and determining the concentration through direct electrical measurements, arising from the change in the redox state of the analyte, and monitored through classical electroanalytical techniques. Remarkably, recent achievements in nanoscience and nanotechnology, have demonstrated the potential for improving greatly both the sensitivity and selectivity of electrochemical sensors and biosensors. In fact, an electrochemical sensor can be miniaturized to a size less than one micrometer or to small-size arrays of nano-electrodes, offering advantages in terms of increased sensitivity and compactness (NEA). The attractiveness of such nanostructured systems resides also in the possibility to immobilized biomolecules on the dielectric surface surrounding each nanoelectrode, instead of on the electrode itself. Therefore, in NEAs, where the electrochemical properties of the electrode and the physical-chemical properties of the dielectric surface may be optimized independently, it may result easier to combine the highly specific molecular recognition mechanisms with high sensitivity (low detection limits). The aim of this work is the development of nanostructured electrochemical and electrochemiluminescence-based sensors for the detection of biomolecules, such as DNA and proteins. The fabrication of arrays of nanoelectrodes was performed by deposition of a thin film of polycarbonate (PC) as insulator on a layer of Boron Doped Diamond (BDD) or Glassy Carbon (GC). NEAs were obtained by creating an array of nanoholes in the polymeric film using two different nanofabrication techniques: electron beam lithography (EBL) and nanoimprint lithography (NIL). These approaches lead to the formation of recessed nanoelectrodes. Particulary, the optimization of the parameters to fabricate NEAs by nanoimprint lithography (NIL) has allowed to reduce time and manufacturing costs. We demonstrate the possibility to efficiently immobilize biomolecules, on the relatively large surface of the PC of our NEAs in order to develop sensitive electrochemical biosensors. Initially, the sensors were tested for the detection of HPV (Human Papilloma Virus) DNA sequences. Later we focused on the optimization of the protocol for the detection of proteins by enzyme immuno-assay with the enzyme Horse Radish Peroxidase (HRP), using Gliadin and Tumor necrosis factor (TNF-α) as target. The process of bio-recognition and detection was carried out by cyclic voltammetry and consists of an immuno-indirect scheme. This method allows to detect a concentration of 0.1 nM for Gliadin fragment and the experiments performed indicate the possibility to further low this limit. The same samples were tested at the Institut des Sciences Molèculaires University of Bordeaux (Group of Nanosystèmes Analitique) using electrochemiluminescence (ECL). In these sensors the transduction scheme involves a secondary antibody labbeled with Biotin, that provides a strong interaction with the complex streptavidin- Ru(bpy)32+. The ECL signal obtained in the presence of the co-reactant tripropylamine (TPrA) was recorded using both a CCD camera and a photomultiplier tube. Furthemore, additional sensors have been prepared using GC as conductive material and PC as insulating layer.

ECL is luminescence generated by electrochemical reactions and for this reason it possesses better spatio-temporal control and low background in comparison with photoluminescence or other optical methods that rely on external light illumination.1–3 In the last 20 years ECL has proved to be a versatile and powerful analytical technique in different fields, ranging from fundamental research to commercial clinical and biological applications.4,5 The main reason behind its success is that ECL offers remarkable advantages in comparison to other transduction methods: high sensitivity, an extremely wide dynamic range, very low background signal, good temporal and spatial control, and insensitivity to matrix effects.6,7 Thanks to its simplified optical setup, ECL has been implemented as a powerful imaging technique to visualize electrochemical objects and entities bringing important insight in the ECL mechanism generation. Here we aim to incorporate all the work done in the field of ECL imaging mainly in the last three years with a particular focus on ECL generation mechanisms and their applications.

The coupling of nanomaterials, and nanoparticles in particular, with one of the most powerful transduction techniques, electrochemiluminescence (ECL), i.e., chemiluminescence triggered by electrochemical reactions at electrodes, has recently provided sensing tools with unprecedented sensitivity limits. This review aims to give an overview of the state of the art in the field over the last 5 years, i.e., a time span covering over 80% of the scientific production in this context. The results herein discussed would demonstrate that the use of nanoparticles in the ECL technique represents one of the most interesting research lines for the development of ultrasensitive analytical tools, offering an insight to recognize and select the best nanomaterials for ECL signal amplification, with particular emphasis in biosensing. (C) 2018 Elsevier B.V. All rights reserved.

Nanoelectrode arrays (NEAs) are increasingly applied for a variety of electroanalytical applications; however, very few studies dealt with the use of NEAs as an electrochemical generator of electrogenerated chemiluminescence (ECL). In the present study, arrays of nanodisc and nanoband electrodes with different dimensions and inter-electrode distances were fabricated by e-beam lithography on a polycarbonate layer deposited on boron-doped diamond (BDD) substrates. In particular, NEAs with 16 different geometries were fabricated on the same BDD sample substrate obtaining a multiple nanoelectrode and ultramicroelectrode array platform (MNEAP). After electrochemical and morphological characterization, the MNEAP was used to capture simultaneously with a single image the characteristic behaviour of ECL emission from all the 16 arrays. Experiments were performed using Ru(bpy)(3) (2+) as the ECL luminophore and tri-n-propylamine (TPrA) as the co-reactant. With a relatively limited number of experiments, such an imaging procedure allowed to study the role that geometrical and mechanistic parameters play on ECL generation at NEAs. In particular, at high concentrations of TPrA, well-separated individual ECL spots or bands revealed an ECL signal which forms a pattern matching the nanofabricated structure. The analysis of the imaging data indicated that the thickness of the ECL-emitting zone at each nanoelectrode scales inversely with the co-reactant concentration, while significantly stronger ECL signals were detected for NEAs operating under overlap conditions. Supplementary material: [http://cherry.chem.bg.ac.rs/handle/123456789/3566]

Glucocorticoids are universally used in the treatment of acute lymphoblastic leukemia (ALL), and resistance to glucocorticoids in leukemia cells confers poor prognosis. To elucidate mechanisms of glucocorticoid resistance, we determined the prednisolone sensitivity of primary leukemia cells from 444 patients newly diagnosed with ALL and found significantly higher expression of CASP1 (encoding caspase 1) and its activator NLRP3 in glucocorticoid-resistant leukemia cells, resulting from significantly lower somatic methylation of the CASP1 and NLRP3 promoters. Overexpression of CASP1 resulted in cleavage of the glucocorticoid receptor, diminished the glucocorticoid-induced transcriptional response and increased glucocorticoid resistance. Knockdown or inhibition of CASP1 significantly increased glucocorticoid receptor levels and mitigated glucocorticoid resistance in CASP1-overexpressing ALL. Our findings establish a new mechanism by which the NLRP3-CASP1 inflammasome modulates cellular levels of the glucocorticoid receptor and diminishes cell sensitivity to glucocorticoids. The broad impact on the glucocorticoid transcriptional response suggests that this mechanism could also modify glucocorticoid effects in other diseases.