Circumventing Traditional Conditioning Protocols in Polymer Membrane-Based Ion-Selective Electrodes

Preparation of ion-selective electrodes (ISEs) often requires long and complicated conditioning protocols limiting their application as tools for in-field measurements. Herein, we eliminated the need for electrode conditioning by loading the membrane cocktail directly with primary ion solution. This proof of concept experiment was performed with iodide, silver, and sodium selective electrodes. The proposed methodology significantly shortened the preparation time of ISEs, yielding functional electrodes with submicromolar detection limits. Moreover, it is anticipated that this approach may form the basis for the development of miniaturized all-solid-state ion-selective electrodes for in situ measurements

Clonal chromosomal mosaicism and loss of chromosome Y in elderly men increase vulnerability for SARS-CoV-2

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, COVID-19) had an estimated overall case fatality ratio of 1.38% (pre-vaccination), being 53% higher in males and increasing exponentially with age. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, we found 133 cases (1.42%) with detectable clonal mosaicism for chromosome alterations (mCA) and 226 males (5.08%) with acquired loss of chromosome Y (LOY). Individuals with clonal mosaic events (mCA and/or LOY) showed a 54% increase in the risk of COVID-19 lethality. LOY is associated with transcriptomic biomarkers of immune dysfunction, pro-coagulation activity and cardiovascular risk. Interferon-induced genes involved in the initial immune response to SARS-CoV-2 are also down-regulated in LOY. Thus, mCA and LOY underlie at least part of the sex-biased severity and mortality of COVID-19 in aging patients. Given its potential therapeutic and prognostic relevance, evaluation of clonal mosaicism should be implemented as biomarker of COVID-19 severity in elderly people. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, individuals with clonal mosaic events (clonal mosaicism for chromosome alterations and/or loss of chromosome Y) showed an increased risk of COVID-19 lethality

Determination of glutathione in hemolysed erythrocyte with amperometric sensor based on TTF-TCNQ

Background: GSH has a relevant role in human metabolism as an indicator of disease risks. An amperometric sensor for glutathione (GSH) determination is described as an alternative method featuring simple construction procedure and short time analysis. Method: The developed sensor was used to determine glutathione at low potential using a TTF-TCNQ complex. Results: The sensor exhibits a linear response range from 5 to 340 mu mol/l under applied potential of 200 mV vs. SCE. The sensitivity and detection limit were 90.1 mu A l/mmol cm(2) and 0.3 mu mol/l, respectively. Conclusion: When the sensor was tested in hemolysed erythrocyte samples for GSH determination, a good correlation in results was observed between the sensor and the spectrophotometric method. The sensor showed recovery values between 98% and 102%. (c) 2006 Elsevier B.V All rights reserved.3714167115215

Determination of reduced glutathione using an amperometric carbon paste electrode chemically modified with TTF-TCNQ

The development of an amperometric sensor for the determination of reduced glutathione (GSH) is described. The sensor is based on tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) incorporated into the graphite powder/Nujol oil matrix. The electrooxidation of GSH was monitored amperometrically at 200 mV versus SCE (saturated calomel electrode). The amperometric response of the sensor was linearly proportional to the GSH concentration between 20 and 300 mumol l(-1), in 0.1 mol l(-1) phosphate buffer (pH 8.0), containing 0.1 mol l(-1) KCl and 0.5 mmol l(-1) Na(2)H(2)EDTA, as supporting electrolyte. The detection limit, considering signal/noise ratio equal three, was 4.2 mumol l(-1) for GSH and the repeatability obtained as relative standard deviation was of 5.1 % for a series of 10 successive measurements. (C) 2004 Elsevier B.V. All rights reserved.100333334

Electroanalytical determination of acid phosphatase activity by monitoring p-nitrophenol

The development of a modified electrode for the selective determination of p-nitrophenol (PNP) to be applied in the determination of the enzymatic activity (EA) of acid phosphatase using p-nitrophenylphosphate (PNPP) as substrate is described. Elimination of the interference of PNPP was made by covering the electrode surface using 25 mul of a 5% (m/v) Nafion (R) solution. In comparison to the glassy carbon (GC) electrode without modification, the presence of the membrane promoted a reduction in the sensitivity and an increase in the detection limit for the determination of PNP, in addition to a decrease of the electron transfer constant. The GC electrode covered with a Nafion (R) membrane showed a linear response range between 20 and 230 mu mol l(-1) for PNP, adjusted by the equation I-p = 0.157 + 0.0089 [PNP], for N = 22 with a correlation coefficient of 0.9984. This electrode was used for the determination of the EA of acid phosphatase from castor bean seeds and an activity of 38.40 U mg(-1) was found. (C) 2001 Elsevier Science B.V. All rights reserved.441220721

High-Temperature Potentiometry: Modulated Response of Ion-Selective Electrodes During HeatPulses

The concept of locally heated polymeric membrane potentiometric sensors is introduced here for the first time. This is accomplished in an all solid state sensor configuration, utilizing poly(3-octylthiophene) as the intermediate layer between the ion-selective membrane and underlying substrate that integrates the heating circuitry. Temperature pulse potentiometry (TPP) gives convenient peak-shaped analytical signals and affords an additional dimension with these sensors. Numerous advances are envisioned that will benefit the field. The heating step is shown to give an increase in the slope of the copperselective electrode from 31 to 43 mV per 10-fold activity change, with a reproducibility of the heated potential pulses of 1% at 10 M copper levels and a potential drift of 0.2 mV/h. Importantly, the magnitude of the potential pulse upon heating the electrode changes as a function of the copper activity, suggesting an attractive way for differential measurement of these devices. The heat pulse is also shown to decrease the detection limit by half an order of magnitude

A Universal And Label-Free Impedimetric Biosensing Platform For Discrimination Of Single Nucleotide Substitutions In Long Nucleic Acid Strands

We report a label-free universal biosensing platform for highly selective detection of long nucleic acid strands. The sensor consists of an electrode-immobilized universal stem-loop (USL) probe and two adaptor strands that form a 4J structure in the presence of a specific DNA/RNA analyte. The sensor was characterized by electrochemical impedance spectroscopy (EIS) using K3[Fe(CN)6]/K4[Fe(CN)6] redox couple in solution. An increase in charge transfer resistance (RCT) was observed upon 4J structure formation, the value of which depends on the analyte length. Cyclic voltammetry (CV) was used to further characterize the sensor and monitor the electrochemical reaction in conjunction with thickness measurements of the mixed DNA monolayer obtained using spectroscopic ellipsometry. In addition, the electron transfer was calculated at the electrode/electrolyte interface using a rotating disk electrode. Limits of detection in the femtomolar range were achieved for nucleic acid targets of different lengths (22 nt, 60 nt, 200 nt). The sensor produced only a background signal in the presence of single base mismatched analytes, even in hundred times excess in concentration. This label-free and highly selective biosensing platform is versatile and can be used for universal detection of nucleic acids of varied lengths which could revolutionize point of care diagnostics for applications such as bacterial or cancer screening