Dynamics of Redox Processes in Ionic Liquids and Their Interplay for Discriminative Electrochemical Sensing

Motivated by the use of ionic liquids (ILs) as green replacers of traditional electrolytes, a mechanistic study has been systematically conducted to comprehend various design principles responsible for electrochemical profiling of redox-active species in ILs. The full spectrum of properties associated with ILs is exploited to assess the viability of this platform, thus revealing the correlation between the redox properties and the physiochemical parameters of the species involved. This includes the evaluation of (1) the variation of redox responses toward analytes with similar molecular structures or functionalities of ILs, (2) the influence in terms of physical criteria of the system such as viscosity and conductivity as well as chemical structure of ILs, and (3) the sustainability in harsh conditions (high temperature or humidity) and interferences. The principle is exemplified via trinitrotoluene (TNT) and dinitrotoluene (DNT) with inherent redox activity as analytes and IL membranes as solvents and electrolytes using glassy carbon (GC) electrodes. A discrete response pattern is generated that is analyzed through linear discriminant analysis (LDA) leading to 100% classification accuracy even for the mixture of analytes. Quantitative analysis through square wave voltammetry (SWV) gave rise to the detection limits in liquid phase of 190 and 230 nM for TNT and DNT, respectively, with a linear range up to 100 μM. Gas-phase analysis shows strong redox signals for the estimated concentrations of 0.27 and 2.05 ppm in the gas phase for TNT and DNT, respectively, highlighting that ILs adopt a role as a preconcentrator to add on sensitivity with enhanced selectivity coming from their physiochemical diversity, thus addressing the major concerns usually referred to most sensor systems

Study of Ionic Liquid Immobilization on Polyvinyl Ferrocene Substrates for Gas Sensor Arrays

In this report, the effects of conductive polymer oxidation states and structures on the design and development of ionic liquid (IL)/conductive polymer (CP) composite films for gas sensing are systematically characterized. Four different polyvinyl ferrocene (PVF) films synthesized by varying the conditioning potential (0.7 vs 0.0 V) and the electrolyte are tested for their gas-sensing properties (e.g., sensitivity, selectivity, response time, linearity, and dynamic range against various gas analytes such as dichloromethane, ethanol, natural gas, methane, formaldehyde (37%), and benzene) utilizing the quartz crystal microbalance (QCM) and ATR-FT-IR. The best available film is further studied as a substrate for the immobilization of various ILs that enhanced both the sensitivity and selectivity. Finally, two arrays, each comprising four sensors with the following scheme are developed and characterized for their ability to classify the four target analytes by using linear discriminant analysis: (1) the highest sensitivity PVF film immobilized with four different ILs and (2) the highest sensitivity IL immobilized in four different PVF films. Array 2 is proven to be much better than array 1 in discriminating the analytes, which is very significant in establishing the fact that a diverse set of PVF redox states allow the rational development of a PVF/IL composite-based sensor array in order to analyze complex mixtures utilizing structural differences and the extent of intermolecular interactions

Additional file 1: Table S1. of Role of a common variant of Fat Mass and Obesity associated (FTO) gene in obesity and coronary artery disease in subjects from Punjab, Pakistan: a case control study

Primers and Probes for TaqMan Assay. (DOCX 10 kb

Antimicrobial Susceptibility Assays Based on the Quantification of Bacterial Lipopolysaccharides via a Label Free Lectin Biosensor

A label free lectin biosensor developed in our laboratory that can quantitatively measure the binding between the lectin immobilized at the carbohydrate sensor surface and the lipopolysaccharide (LPS) on Gram-negative bacteria was demonstrated for an antibiotic susceptibility assay. The biosensor utilizes a polythiophene interface containing fused quinone moieties glycosylated to form a carbohydrate platform for the immobilization of Concanavalin A (Con A) and is capable of LPS binding measurements via orthogonal quartz crystal microbalance and electrochemical readouts (EQCM). Such orthogonal transduction provides cross-validation, better sensor sensitivity, and a large dynamic range of the measurements. We have applied this label free lectin biosensor for a new antibiotic susceptibility assay by characterizing the antimicrobial activities of various antibiotics (i.e., ciprofloxacin, ceftriaxone, and tetracycline) against Escherichia coli W1485 as a model system. The label free biosensor allows both end point and real time measurements of antibiotic effects on the bacterial cell surface LPS, which is shown to correlate to their antibiotic effects. At the end point, after 18 h incubation of bacterial cells with these three antibiotics respectively, the bacterial LPS binding signal was reduced to 23%, 27%, and 38%, respectively, for the three antibiotics, indicating that ciprofloxacin is the most effective against this E. coli strain. Real time measurements at the 1 h time point showed a similar trend with a reduction of binding to 91%, 93%, and 95%, respectively. From the binding kinetics of these measurements, the relaxation time (τ) was obtained, where higher τ value means slow binding interactions between the lectin and the bacterial LPS. The obtained order of τ, (i.e., τ_{ciprofloxacin} > τ_ceftriaxone > τ_tetracycline) again indicated that ciprofloxacin has more bactericidal activity than the other two antibiotics with the same concentrations. Thus, we are able to establish that the reduction in the binding of LPS with the lectin Con A sensor upon exposure to various antibiotics has a direct relation with the antibiotic dosages making this label free biosensor assay promising for therapeutic management of these drugs as well as for applications in antibiotic research and development

1DE analysis of IAF-labelled <i>T. asahii</i> proteins.

<p>Proteins (150 µg) extracted from <i>T. asahii</i> were labelled with 0.2 mM IAF and subjected to 1DE. The gels were scanned for IAF fluorescence in a Typhoon scanner followed by staining in colloidal coomassie. Panel A shows coomassie-stained gels whilst panel B is the corresponding IAF fluorescence image. Changes in total spot intensity between treated and untreated cells were quantified by Image Quant software analysis (Panel C).</p

Relative specific activities for GR (panel A) and GST (panel B) in <i>T. asahii</i> cultures exposed to CdCl₂ and NaAsO₂.

<p>Values are expressed as mean of SD and experiments were performed in triplicate (*p<0.05; **p<0.1 when compared with controls).</p

List of plants collected from SD with their accession numbers and relevant details.

List of plants collected from SD with their accession numbers and relevant details.</p

Weaving the basket and brooms for commercial purpose <i>Nannorhops ritchieana</i>.

Weaving the basket and brooms for commercial purpose Nannorhops ritchieana.</p

Growth curves for <i>T. asahii</i> cultures grown in the presence of 100 mg/L CdCl2 (green) and NaAsO2 (red).

<p>Growth curves for <i>T. asahii</i> cultures grown in the presence of 100 mg/L CdCl2 (green) and NaAsO2 (red).</p

Relative specific activities for CAT (panel A) and SOD (panel B) in <i>T. asahii</i> extracts from yeast cultured in the presence of CdCl₂ and NaAsO₂.

<p>Values are expressed as mean of SD and experiments were performed in triplicate.</p