Single step grown MoS2 on pencil graphite as an electrochemical sensor for guanine and adenine: A novel and low cost electrode for DNA studies

Application of eco‐friendly disposable pencil graphite sensor for electrochemical evaluation and determination of podophyllotoxin using in cancer treatment

A sensitive, simple and selective voltammetric method was developed for the quantification of plant‐derived podophyllotoxin, which is included in antineoplastic drugs, using a disposable pencil graphite electrode. Using the square‐wave voltammetry technique, podophyllotoxin gave a very good voltammetric response at +1.24 V (vs. Ag/AgCl) potential (at 0.0 V and after 60 s pre‐concentration) in Britton Robinson (pH 4.0) media. This procedure was used to detection the compound in the concentration range of 12.4–299.5 nM with a limit of detection to 2.62 nM (1.08 μg L−1). The proposed method has been successfully applied to human urine samples.

Highly selective detection of adenine and guanine by NH2-MIL-53(Fe)/CS/MXene nanocomposites with excellent electrochemical performance

Adenine (A) and guanine (G) are mainly found in deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) and play a crucial role in genetic information transfer and protein synthesis. In this study, NH₂-MIL-53(Fe)/CS/MXene nanocomposites were prepared for detecting guanine and adenine. With high specific surface area, excellent water dispersion, and numerous active sites, MXene (transition metal carbides, nitrides, and carbonitrides) provides a good platform for loading primitive metal-organic frameworks (MOFs). At the same time, the problem of poor conductivity and dispersion of MOFs is solved. The electrochemical catalytic oxidation of adenine and guanine of NH₂-MIL-53 (Fe)/CS/MXene nanocomposites was carried out by differential pulse voltammetry (DPV). Operating voltage of DPV: 0.7-0.9 V (vs. Ag/AgCl) for G, 1.0-1.2 V (vs. Ag/AgCl) for A, 0.8 V (vs. Ag/AgCl), and 1.1 V (vs. Ag/AgCl) for G and A. The concentration ranges for detecting A and G were 3-118 μM and 2-120 μM with detection limits of 0.57 μM and 0.17 μM (S/N = 3), respectively. The nanocomposite was used for detecting G and A in herring sperm DNA, and the content of G and A was found to be about 9 and 11 μM; the RSD values were 3.4 and 1.3%, respectively.

A Micro Electrochemical Sensor for Multi-Analyte Detection Based on Oxygenated Graphene Modified Screen-Printed Electrode

Electrode interfaces with both antibiofouling properties and electrocatalytic activity can promote the practical application of nonenzymatic electrochemical sensors in biological fluids. Compared with graphene, graphene oxide (GO) possesses unique properties such as superior solubility (hydrophilicity) in water, negative charge, and abundant oxygenated groups (oxo functionalities) in the plane and edge sites, which play an essential role in electrocatalysis and functionalization. In this work, a micro electrochemical sensor consisting of GO-modified screen-printed electrode and PDMS micro-cell was designed to achieve multi-analyte detection with excellent selectivity and anti-biofouling properties by electrochemically tuning the oxygen-containing functional species, hydrophilicity/hydrophobicity, and electrical conductivity. In particular, the presented electrodes demonstrated the potential in the analysis of biological samples in which electrodes often suffer from serious biofouling. The interaction of proteins with electrodes as well as uric acid was investigated and discussed.

Non-Coding RNA-Based Biosensors for Early Detection of Liver Cancer

Primary liver cancer is an aggressive, lethal malignancy that ranks as the fourth leading cause of cancer-related death worldwide. Its 5-year mortality rate is estimated to be more than 95%. This significant low survival rate is due to poor diagnosis, which can be referred to as the lack of sufficient and early-stage detection methods. Many liver cancer-associated non-coding RNAs (ncRNAs) have been extensively examined to serve as promising biomarkers for precise diagnostics, prognostics, and the evaluation of the therapeutic progress. For the simple, rapid, and selective ncRNA detection, various nanomaterial-enhanced biosensors have been developed based on electrochemical, optical, and electromechanical detection methods. This review presents ncRNAs as the potential biomarkers for the early-stage diagnosis of liver cancer. Moreover, a comprehensive overview of recent developments in nanobiosensors for liver cancer-related ncRNA detection is provided.

Nonmetallic SERS-based immunosensor byintegrating MoS2 nanoflower and nanosheet towards the direct serum detection of carbohydrate antigen 19-9

Recently, nonmetallic substrates have stimulated great interest in surface-enhanced Raman scattering (SERS)-based immunoassay owing to their good uniformity, stability, and biocompatibility. In this context, a novel nonmetallic SERS-based immunoassay mediated by two-dimensional molybdenum disulfide (MoS₂) was delivered for the sensitive and specific monitoring of carbohydrate antigen 19-9 (CA19-9). The effective enrichment of molecules on the large active surfaces of MoS₂ as well as potential 532-nm laser-induced charge transfer resonances between them engendered desirable enhancement factor values at the level of 10⁵. Intriguingly, a sandwich immunocomplex combined MoS₂ nanoflower and nanosheet exhibited not only a wide linear range from 5 × 10^-4 to 1 × 10² IU·mL^-1 but also a limit of detection as low as 3.43 × 10^-4 IU·mL^-1 towards CA19-9. More meaningful, the analytical result for clinical patient serum sample was basically compared with the conventional chemiluminescent immunoassay. Such a novel nonmetallic SERS-based immunosensor with desirable biocompatibility and sensitivity is promising for clinical diagnosis.

A copper-based metal–organic framework/graphene nanocomposite for the sensitive and stable electrochemical detection of DNA bases

A simple and easy-operation electrode modification strategy was proposed using Cu-MOF/GO nanohybrids for physiologists and pathologists for the feasible and reliable simultaneous electrochemical detections of DNA bases, namely guanine and adenine.

Charge Transfer Platform and Catalytic Amplification of Phenanthroimidazole Derivative: A New Strategy for DNA Bases Recognition

Research about DNA composition has been concentrated on DNA damage in the past few decades. However, it still remains a great challenge to construct a rapid, facile, and accurate approach for simultaneously monitoring four DNA bases, guanine (G), adenine (A), thymine (T), and cytosine (C). Herein, a novel electrochemical sensor based on phenanthroimidazole derivative, 2-(4-bromophenyl)-1-phenyl-1H-phenanthro[9,10-d]-imidazole (PPI), is successfully fabricated by a simple electrochemical method. The bromophenyl group in PI could expand their aromatic plane, induce the π-conjugated extension, and enhance the charge transfer and π-π interaction. The phenyl group at N1 position could regulate the intermolecular interaction, which could promote the possibility of intermolecular connection. The PPI polymer (poly(PPI)) with π-electron enriched conjugation architecture has been applied in simultaneous determination of G, A, T, and C in neutral solution by square wave voltammetry (SWV) method with well-separated peak potentials at 0.714, 1.004, 1.177, and 1.353 V, respectively. The sensor functionalized with poly(PPI) exhibits wide linear response for G, A, T, and C in the concentration ranges of 3-300, 1-300, 30-800, and 20-750 μM, respectively. With favorable selectivity, stability, and reproducibility, the sensor is successfully utilized to monitor four DNA bases in real samples, displaying a promising prospect for electrochemical sensing devices.

Large area, one step synthesis of NiSe2 films on cellulose paper for glucose monitoring in bio-mimicking samples for clinical diagnostics

There is an urgent need to develop low cost electrochemical sensors wherein the sensor can be disposed after recording data, thereby eliminating the issue of inaccuracy arising from repeated sensing measurements, which plagues most conventional electrochemical sensors. This work is the first demonstration of a NiSe₂ based disposable, one time use electrochemical glucose sensor in bio-mimicking real samples wherein NiSe₂ was hydrothermally grown NiSe₂ on a biodegradable cellulose paper. Both physicochemical (x-ray diffraction, x-ray photoelectron spectroscopy, field emission scanning electron microscope) and electrochemical (impedance spectroscopy and cyclic voltammetry (CV)) characterization techniques confirmed the growth and presence of NiSe₂ on a cellulose paper. Electrochemical techniques like CV and amperometric (i-t) were utilized for the selective and sensitive oxidation of glucose. The results suggests that the proposed NiSe₂ sensor is effective in a linear range of 0.1-1 mM with fast response time (3.9 s), low detection limit (24.8 ± 0.1 μM) and high sensitivity (0.25 A M^-1 cm^-2) at a potential applied (E _app = 0.55 V versus Ag∣AgCl). Prior to the real sample analyses i.e. glucose detection in human urine, the fabricated NiSe₂ sensor was tested for selectivity towards glucose in co-existing interferences (dopamine, ascorbic acid, uric acid, urea, sodium chloride, fructose, lactose and cysteine). Finally, glucose in artificial blood serum and urine samples was demonstrated with the fabricated NiSe₂ sensor and the results are comparable to the conventional laboratory methods. The present methodology presents a novel possibility towards the design of next generation, affordable point-of-care devices for a broad range of clinical diagnostics.

One-Step Synthesis of MoS2/TiSi2 via an In Situ Photo-Assisted Reduction Method for Enhanced Photocatalytic H2 Evolution under Simulated Sunlight Illumination

A new MoS2/TiSi2 complex catalyst was designed and synthesized by a simple one-step in situ photo-assisted reduction procedure. The structural and morphological properties of the composites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and ultraviolet-visible diffused reflectance spectroscopy (UV-vis DRS), which proved the formation of MoS2/TiSi2. MoS2/TiSi2 with optimized composition showed obviously enhanced photocatalytic activity and superior durability for water reduction to produce H2. The H2 generation rate over the MoS2/TiSi2 photocatalyst containing 3 wt % MoS2 reached 214.1 μmol·h−1·g−1 under visible light irradiation, which was ca. 5.6 times that of the pristine TiSi2. The improved photocatalytic activity of MoS2/TiSi2 could be related to the broad response spectrum, large visible light absorption, and synergies among MoS2 and TiSi2 that enhance photoexcited charge transfer and separation.