Double-antibody-based nano-biosensing systemfor the onsite monitoring of SARS-CoV-2 variants

The fast and reliable diagnosis of COVID-19 is the foremost priority for promoting public health interventions.Therefore, double-antibody-based immunobiosensor chips were designed, constructed, and exploited for clinicaldiagnosis. Gold nanoparticles/tungsten oxide/carbon nanotubes (AuNPs/WO3/CNTs) were used as the active workingsensor surface to support the chemical immobilization of a mixture of SARS-CoV-2 antibodies (anti-RBD-S and anti-RBD-S-anti-Llama monoclonal antibodies). The morphology and chemical functionalization of the fabricateddisposable immunochips was characterized using scanning electron microscopy (SEM), Fourier transform infrared(FTIR) spectroscopy, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). After full assayoptimization, the immunobiosensor showed a high sensitivity to detect SARS-CoV-2-S protein with limits of detectionand quantification of 1.8 and 5.6 pg/mL, respectively. On the other hand, for the SARS-CoV-2 whole virus particleanalysis, the detection and quantification limits were determined to be 5.7 and 17 pg/mL, respectively. The biosensorshowed a highly selective response toward SARS-CoV-2, even in the presence of influenza, nontargeting humancoronaviruses, and Middle East respiratory syndrome coronavirus (MERS-CoV). The immunochips exhibited distinctresponses toward the variants of concern: B.1>C.36.3>Omicron> Delta> Alpha coronavirus variants. For biosensorvalidation, twenty-nine clinical specimens were analyzed, and the impedimetric responses were positively detected fortwo Delta samples, eighteen Omicron samples, and six B.1-type samples in addition to three negative samples.Eventually, the immunobiosensor was fabricated in the form of ready-to-use chips capable of sensitive detection ofvirus variants, especially variants of concern (VOC) and interest, in a specimen within 15 min. The chips providedinstantaneous detection with the direct application of clinical samples and are considered a point-of-care device thatcould be used in public places and hot spots.

Manganese dioxide(MnO_(2))/Fullerene-C_(60)-Modified Electrodes for the Voltammetric Determination of Rifaximin

Rifaximin(RFX)is a broad-spectrum oral antibiotic with bactericidal actions against Gram-negative and Gram-positive bacteria.In the present work,a sensitive voltammetric assay for the RFX in pharmaceutical formulations is designed using nanostructured working electrodes.Surface functionalization with manganese dioxide(MnO_(2))/fullerene-C_(60) nanocomposite exhibited the highest electrochemical responses with a sharp oxidation peak at about 336 mV that was obtained using the differential pulse voltammetry(DPV).The cyclic voltammetry(CV)and electrochemical impedance spectroscopy(EIS)were applied,while the electrode matrix composition including types of nanomaterials,electroanalytical parameters,and pH eff ect were optimized.To that end,using the DPV,high sensitivity was obtained from the linear calibration curve ranged from 0.8 to 31.5μg·mL^(-1) with the correlation coe fficient of 0.99,limit of detection of 0.76μg·mL^(-1) and limit of quantification of 2.31μg·mL^(-1) .Accordingly,the designed approach is off ering a potential applicability towards the RFX determination in pharmaceutical preparations and its quality control.