Poly(vinylferrocenium) coated disposable pencil graphite electrode for DNA hybridization

Poly(vinylferrocenium) (PVF⁺) modified electrode was developed in this study for the electrochemical sensing of DNA based on the oxidation signals of polymer, adenine and guanine. Experimental parameters, such as; polymeric film thickness, DNA immobilization time and DNA concentration were examined in order to obtain more sensitive and selective electrochemical signals. After optimization studies, DNA hybridization was investigated.     

Use of averages of patient data for quality control

Applicability of Hoffman's average of normals (AON) method was evaluated in quality control (QC) for twenty clinical chemistry assays (ALT, Alb, ALP, AMY, AST, T. Bil, inP, Glu, Ca, Cl, T. Chol, Creat, CK, K, LD, T. Prot., Na, TG, BUN, Uric. A.) performed routinely in the Hospital of Medical Faculty of 9 Eylül University. Consecutive Texas Instruments XL-Dacos patient data were accumulated over 10 days. According to the guidelines developed by Cembrowsky et. al. for the implementation of average of patients (AOP) (also known as AON) procedure, the patient population mean, *_p, population standard deviation, S_p, the ratio of S_p/S_a (S_a, the analytical standard deviation), and the approximate number of patient results averaged. Np (with P_ed=0.50) were determined from the nomogram constructed by Cembrowsky et. al., illustrating the relationship between Np, S_p/S_a, and the probability of detecting a 2S_a shift (P_ed) when the probability of false rejection, P_fr, is 0.01. The control limits and the truncation limits were selected as *_p±2Sp and *_p±2.58×Sp√Np, respectively. The estimated values were assessed for the applicability of AOP procedures in the clinical laboratory. We conclude that the AOP procedure is a valuable tool for instrument monitoring as an adjunct to more costly standard QC procedures and is also an efficient, cost-effective and rapid way of collecting appropriate information on large number of patients.     

A practical analytical quality report on the effect of carotenemia on neonatal bilirubin levels

 The effect of haematocrit and β-carotene levels on the serum total bilirubin measurement in two analytical methods was studied as an example of the impact of practical analytical quality in medical decision making. The precision characteristics of the two methods were very similar. Based upon the significant difference in the correlation coefficient in a method comparison study before and after 20% trimming of the data, an interference effect study was performed. Haemoglobin (expressed as haematocrit) and β-carotene were the substances studied to explain the observed differences. The bilirubin test results from the Wako bilirubinometer were easily affected (n=19;X(S): 13.83±2.43;t=–6.17;P=0.000) and more elevated than in the Vitros dry chemistry systems (n=18;X(S): 12.72±2.21;t=–2.48;P=0.017), due to the presence of β-carotene (>200 μg/dl).     

Constant Current Chronopotentiometry and Voltammetry of Native and Denatured Serum Albumin at Mercury and Carbon Electrodes

Constant current chronopotentiometric peak H at mercury electrodes was recently shown as a sensitive tool for global and local changes in protein conformation [1]. Large differences between the heights of peak H of native (hBSA_nat) and denatured BSA (hBSA_den) were observed. The ratio hBSA_den/hBSA_nat increased with more negative stripping current suggesting that the rate of potential change is important for discrimination between native and denatured BSA. Voltammetric peaks of BSA were less well developed and BSA_den/BSA_nat was much smaller. It was not possible to discriminate BSA_den and BSA_nat using carbon electrodes.     

Highly sensitive disposable nucleic acid biosensors for direct bioelectronic detection in raw biological samples

The development of rapid, low-cost and reliable diagnostic methods is crucial for the identification and treatment of many diseases. Screen-printed gold electrodes (Au/SPEs), coated with a ternary monolayer interface, involving hexanedithiol (HDT), a specific thiolated capture probe (SHCP), and 6-mercapto-1 hexanol (MCH) (SHCP/HDT/MCH) are shown here to offer direct and sensitive detection of nucleic acid hybridization events in untreated raw biological samples (serum, urine and crude bacterial lysate solutions). The composition of the ternary monolayer was modified and tailored to the surface of the Au/SPE. The resulting SHCP/HDT/MCH monolayer has demonstrated to be extremely useful for enhancing the performance of disposable nucleic acid sensors based on screen-printed electrodes. Compared to common SHCP/MCH binary interfaces, the new ternary self-assembled monolayer (SAM) resulted in a 10-fold improvement in the signal (S)-to-noise (N) ratio (S/N) for 1 nM target DNA. The SHCP/HDT/MCH-modified Au/SPEs allowed the direct quantification of the target DNA down to 25 pM (0.25 fmol) and 100 pM (1 fmol) in undiluted/untreated serum and urine samples, respectively, and of 16S rRNA Escherichia coli (E. coli) corresponding to 3000 CFU μL⁻¹ in raw cell lysate samples. The new SAM-coated screen-printed electrodes also displayed favorable non-fouling properties after a 24 h exposure to raw human serum and urine samples, offering great promise as cost-effective nucleic acid sensors for a wide range of decentralized genetic tests.     

Solvable k-essence cosmologies and modified Chaplygin gas unified models of dark energy and dark matter

This paper is devoted to the investigation of the modified Chaplygin gas model in the context of solvable k-essence cosmologies. For this purpose, we construct equations of state parameter of this model for some particular values of the parameter n. The graphical behavior of these equations are also discussed by using power law form of scalar field. The relationship between k-essence and the modified Chaplygin gas model shows viable results in the dark energy scenario. We conclude that the universe behaves as a cosmological constant, quintessence phase or phantom phase depending upon n.     

Phase space analysis of interacting dark energy in f(T) cosmology

In this paper, we examine the interacting dark energy model in f(T) cosmology. We assume dark energy as a perfect fluid and choose a specific cosmologically viable form f(T) = ????T. We show that there is one attractor solution to the dynamical equation of f(T) Friedmann equations. Further we investigate the stability in phase space for a general f(T) model with two interacting fluids. By studying the local stability near the critical points, we show that the critical points lie on the sheet u* = (c ? 1)v* in the phase space, spanned by coordinates (u, v, ??, T). From this critical sheet, we conclude that the coupling between the dark energy and matter c ?? (?2, 0).     

DNAzyme logic-controlled biofuel cells for self-powered biosensors

The integration of a biosensor employing a DNAzyme logic system within a biofuel cell is presented. The self-powered DNAzyme logic biosensor conforms with INH logic operation and generates power output in accordance with a truth table. The new concept of logic-activated DNAzyme by the input signals has wide-ranging implications in the self-powered diagnostics domain.     

Tin oxide nanoparticles-polymer modified single-use sensors for electrochemical monitoring of label-free DNA hybridization

In this study, SnO₂ nanoparticles (SNPs)-poly(vinylferrocenium) (PVF⁺) modified single-use graphite electrodes were developed for electrochemical monitoring of DNA hybridization. The surfaces of polymer modified and polymer-SNP modified pencil graphite electrodes (PGEs) were firstly characterized by using SEM analysis. The electrochemical behaviours of these electrodes were also investigated using the differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) techniques. The polymer-SNP modified PGEs were then tested for the electrochemical sensing of DNA based on the changes at the guanine oxidation signals. Experimental parameters, such as; different modifications in DNA oligonucleotides, DNA probe concentrations were examined to obtain more sensitive and selective electrochemical signals for nucleic acid hybridization. After optimization studies, DNA hybridization was investigated in the case of complementary of hepatitis B virus (HBV) probe, mismatch (MM), and noncomplementary (NC) sequences.     

Nucleic Acid Integrated Technologies for Electrochemical Point-of-Care Diagnostics: A Comprehensive Review

The need for routine and immediate healthcare monitoring has inspired “near-patient testing” or in other words “point-of-care testing (POCT)”. Therefore, POCT can be defined as laboratory tests that are performed at the patient's bedside or in the immediate vicinity of the incident. Among many POCTs, nucleic acid-based testing has attracted enormous attention for the diagnosis of important genetic, inherited and infectious diseases such as cancer and coronavirus. In this review, we outline the integration of nucleic acids into the remarkable electrochemical point-of-care diagnostics including microfluidic, paper and smartphone-based approaches, CRISPR/Cas and liquid biopsy related systems and DNA damage monitoring.