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A novel genosensor was developed for rotavirus specific cDNA sequence detection. The genosensor was comprised of hierarchical flower-like gold nanostructures, MXene, and polypyrrole (HFGNs/MXene/PPY) nanocomposite as a signal amplification tag, specific antisense ssDNA oligonucleotide as a recognition bioelement, and methylene blue (MB) as a redox marker. The morphological and electrochemical features of the biosensor were first tested and optimized and the high performance of the platform was confirmed in terms of sensitivity and reproducibility. Then, 20 rotavirus RNA isolated from clinical and cell-cultured samples (10 positive and 10 negative confirmed by RT-PCR and electrophoresis methods) were evaluated by the genosensor. The analysis results revealed that the genosensor is able to differentiate successfully between the positive and negative control groups. The developed genosensor for rotavirus RNA detection presented an excellent limit of detection of ∼ 0.8 aM and a determination range of 10−18 and 10−7 M. In addition, the ssDNA/HFGNs/MXene/PPY/GCE showed high selectivity and long-term stability of ~ 24 days. Therefore, this novel genosensor would be of great benefit for the clinical diagnosis of rotavirus. [ABSTRACT FROM AUTHOR]

Human T cell leukemia virus type 1 (HTLV‐1) as the first human retrovirus is currently a serious endemic health challenge. Despite the use of assorted molecular or serological assays for HTLV‐1 detection, there are several limitations due to the lack of a confirmatory test that may affect the accuracy of the results. Herein, a novel label‐free biosensor for the detection of HTLV‐1 Tax gene has been reported. An electrochemical facile ecofriendly synthesis method has been demonstrated based on a synthesis of nanocomposite of reduced graphene oxide, polypyrrole, and gold nanoparticles (rGO–PPy–(l‐Cys)–AuNPs) deposited on the surface of screen‐printed carbon electrode. Electrochemical techniques were used to characterize and study the electrochemical behavior of the rGO–PPy–(l‐Cys)–AuNPs, which exhibited a stable reference peak at 0.21 V associated with hybridization forms by applying the differential pulse voltammetry. The designed DNA biosensor presented a wide linear range from 0.1 fM to 100 µM and a low detection limit of 20 atto‐molar. The proposed biosensor presented in this study provides outstanding selectivity, sensitivity, repeatability, and reproducibility. [ABSTRACT FROM AUTHOR]

A bis[1-benzyl-benzimidazoliumethyl]-4-methylbenzenesufonamide bromide ligand (NHCL) as a new type of ionophore was successfully synthesized for the first time and used for the fabrication of Ag + ion selective electrode as a new type of ionophore, based on the self-plasticizing method. The ionophore was characterized using CHN elemental analysis, FT-IR, 1 H NMR, 13 C NMR, UV–vis spectroscopic techniques and X-ray single crystal diffraction. The interection between NHCL and Ag + cation was studied spectrophotometerically and the stoichiometry of the complex (1:2) NHCL:Ag + in DMSO solvent was determined. The potentiometric response of the electrode toward Ag + cation was linear from 2.5 × 10 −6 to 1.0 × 10 −1 M with detection limit of 2.00 × 10 −6 M and a Nernstian slope of 58.48 ± 0.75 mV decade −1 . The sensor exhibited a response time of about 20 seconds at room temperature and working pH range between 3.5–9.0. The electrode showed a good selectivity towards Ag + cations in comparison with other soft and hard metals, while most of these metal ions did not show significant interference ( K A g + , M p o t ). The proposed electrode also applied in the direct determination of Ag + cations in tap water and standard samples with sensible accuracy and precision. [ABSTRACT FROM AUTHOR]

Integrating polypyrrole-cellulose nanocrystal-based composites with glucose oxidase (GOx) as a new sensing regime was investigated. Polypyrrole-cellulose nanocrystal (PPy-CNC)-based composite as a novel immobilization membrane with unique physicochemical properties was found to enhance biosensor performance. Field emission scanning electron microscopy (FESEM) images showed that fibers were nanosized and porous, which is appropriate for accommodating enzymes and increasing electron transfer kinetics. The voltammetric results showed that the native structure and biocatalytic activity of GOx immobilized on the PPy-CNC nanocomposite remained and exhibited a high sensitivity (ca. 0.73 μA·mM-1), with a high dynamic response ranging from 1.0 to 20 mM glucose. The modified glucose biosensor exhibits a limit of detection (LOD) of (50 ± 10) μM and also excludes interfering species, such as ascorbic acid, uric acid, and cholesterol, which makes this sensor suitable for glucose determination in real samples. This sensor displays an acceptable reproducibility and stability over time. The current response was maintained over 95% of the initial value after 17 days, and the current difference measurement obtained using different electrodes provided a relative standard deviation (RSD) of 4.47%. [ABSTRACT FROM AUTHOR]

In this study, a novel procedure for creating cationic response in polypyrrole is introduced. This method was applied to produce an iron II ion selective sensor based on carbon screen-printed electrode in the presence of pyrrole, iron II sulfate, and Sodium dodecyl sulfate (SDS). The formational mechanism of this procedure is discussed. The composition and morphology of the prepared modified electrode is characterized by the Field Emission Scanning Electron Microscope, X-ray Powder Diffraction, and Fourier Transform Infrared Spectrum. The produced iron II sensor can be used for potentiometric and voltammetric detection. The potentiometric dynamic range was 1 × 10 −6 to 1 × 10 −1 M with a Nernstian slope of 29.7 ± 0.5 mV per decade and a detection limit of 8.78 × 10 −7 M. In addition, the differential pulse voltammetry was applied for the optimized electrode and the dynamic range from 1 × 10 −9 to 1 × 10 −5 M with a detection limit of 5.8 × 10 −10 was obtained. The prepared electrode has good potentiometric selectivity for Iron II with respect to several cations. Electrochemical Impedance spectroscopy showed the charge transfer dramatically decreased with optimized electrode. This sensor was successfully used for the determination of iron II concentration in ferrous fumarate tablet using both potentiometric and differential pulse voltammetry methods. [ABSTRACT FROM AUTHOR]

An important issue in the prognosis of tuberculosis (TB) is a short period between correct diagnosis and start the suitable antibiotic therapy. So, a rapid and valid method for detection of Mycobacterium tuberculosis (M. tb) complex is considered as a necessity. Herein, a rapid, low-cost, and PCR-free DNA biosensor was developed based on multi-walled carbon nanotubes (MWCNTs), polypyrrole (PPy), and hydroxyapatite nanoparticles (HAPNPs) for highly sensitive and specific recognition of M.tb. The biosensor consisted of M.tb ssDNA probe covalently attached to the HANPs/PPy/MWCNTs/GCE surface that hybridized to a complementary target sequence to form a duplex DNA. The M.tb target recognition was based on the oxidation signal of the electroactive Methylene Blue (MB) on the surface of the modified GCE using differential pulse voltammetry (DPV) method. It is worth to mention that for the first time Plackett-Burman (PB) screening design and response surface method (RSM) based on central composite design (CCD) was applied as a powerful and an efficient approach to find optimal conditions for maximum M.tb biosensor performance leading to simplicity and rapidity of operation. The proposed DNA biosensor exhibits a wide detection range from 0.25 to 200.0 nM with a low detection limit of 0.141 nM. The performance of designed biosensor for clinical diagnosis and practical applications was revealed through hybridization between DNA probe-modified GCE and extracted DNA from sputum clinical samples. Image 1 • A novel electrochemical DNA biosensor is developed for sensitive detection of M. tb. • PB screening design and RSM were applied to find out the optimum parameter combined for the detection of M. tb. • The used PCR-free electrochemical DNA biosensor is cost-effective and involves no complex and expensive steps. [ABSTRACT FROM AUTHOR]

• Benefiting from the Ti 3 C 2 Mxene amplification, proposed biosensor can detect the M. tb with a detection limit of 112.4 fM. • The biosensor could selectively recognize M. tb in the presence of the bacterial species with high similarity. • Successful analysis of M.tb in the extracted DNA from patient sputum specimens showed high efficiency of this platform. Mycobacterium tuberculosis (M.tb) is a human pathogen due to its slow growth rate and fastidious nature. Tools that can accurately and rapidly track M.tb are vital for the effective treatment of tuberculosis (TB). In present study, a novel genosensor was established for the highly sensitive diagnosis of the specific DNA target inside IS6110 sequence of M.tb genome, using MXene nanosheets and polypyrrole as electrode materials. The multilayer Ti 3 C 2 T x MXene, prepared from the synthesized Ti 3 AlC 2 by delamination process using HCl + LiF solution, presented notable activity in electrocatalysis as an electrode material. Composition information and morphological features of synthesized Ti 3 C 2 T x MXene were studied in detail. Density functional theory (DFT) was applied to explain the structural evolution of Mxene, polypyrrole, nucleotide base, polypyrrole-Mxene hybrid, and nucleotide base-polypyrrole-Mxene intercalation as well as describe their interactions. Under the optimized conditions, the suggested biosensor presented a linear range of 100 fM −25 nM and an excellent coefficient equals 0.9909 and LOD equals 11.24 fM. Experimental results confirmed that this biosensor possessed great sensitivity, stability, and selectivity. This biosensor efficiently determined M.tb in human sputum samples, together with high detection recoveries of 90.52–100.8%. [ABSTRACT FROM AUTHOR]