No abstract

No abstract

In this study, we report on a novel aptasensor based on an electrochemical paper-based analytical device (ePAD) that employs a tungsten disulfide (WS2)/aptamer hybrid for the detection of Listeria monocytogenes. Listeria is a well-known causative pathogen for foodborne diseases. The proposed aptasensor signifies many lucrative features which include simple, cost-effective, reliable, and disposable. Furthermore, the use of an aptamer added more advantageous features in the biosensor. The morphological, optical, elemental composition, and phase properties of the synthesized tungsten disulfide (WS2) nanostructures were characterized by field-emission scanning electron microscopy (FESEM), RAMAN spectroscopy, photoluminescence (PL), and X-ray diffraction (XRD), while electrochemical impedance spectroscopy was performed to corroborate the immobilization of aptamer and to assess the L. monocytogenes sensing performance. The limit of detection (LoD) and limit of quantification (LoQ) of the aptasensor was found to be 10 and 4.5 CFU/mL, respectively, within a linear range of 101–108 CFU/mL. The proposed sensor was found to be selective solely towards Listeria monocytogenes in the presence of various bacterial species such as Escherichia coli and Bacillus subtilis. Validation of the aptasensor operation was also evaluated in real samples by spiking them with fixed concentrations (101, 103, and 105) of Listeria monocytogenes, thereby, paving the way for its potential in a point-of-care scenario.

Norovirus is one of the leading causes of gastroenteritis, acute vomiting, intense diarrhoea, acute pain in the stomach, high fever, headaches, and body pain. Conventional methods of detection gave us very promising results but had disadvantages such as low sensitivity, cost ineffectiveness, reduced specificity and selectivity, etc. Therefore, biosensors can be a viable alternative device which can overcome all setbacks associated with the conventional method. An electrochemical sensor based on oxidized graphitic carbon nitride (Ox-g-C 3 N 4 ) modified electrochemical paper-based analytical device (ePAD) was fabricated for the detection of norovirus DNA. The synthesized Ox-g-C 3 N 4 nanosheets were characterized by field emission scanning electron microscopy (FESEM), X-ray Diffraction (XRD), UV-Vis spectroscopy and X-Ray Photoelectron Spectroscopy. The capture probe DNA (PDNA) modified electrodes were characterized by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). These two characterization techniques were also employed to find the optimal scan rate, response time and temperature of the fabricated sensor. The fabricated biosensor showed a limit of detection (LOD) of 100 fM. Furthermore, the specificity of the reported biosensor was affirmed by testing the response of capture probe DNA with oxidized graphitic carbon nitride (PDNA/Ox-g-C 3 N 4 ) modified ePAD on the introduction of a non-complimentary DNA. The fabricated ePAD sensor is easy to fabricate, cost effective and specific, and requires a minimum analysis time of 5 s. of 11subsequently, need to be hospitalized and around 570-800 of these people die annually [3][4][5]. Food virology research towards the detection of human norovirus has increased manifold after recognizing norovirus as a prominent contributor towards foodborne epidemics [6][7][8]. Conventional methods such as electron microscopy (EM) [9], reverse transcriptase PCR (RT-PCR) assays [10], and enzyme immunoassays (EIAs) [11] were used for detection of the norovirus. These conventional methods gave us very promising results but had their disadvantages such as low sensitivity, cost ineffectiveness, need for experts or professionals to operate the systems, reduced specificity and selectivity [3,12,13]. Hence, biosensors can overcome the shortcomings of the previously used methods of detection such as specificity, sensitivity, and portability [14]. Among them, DNA-based electrochemical biosensors are receiving a lot of attention due to the high specificity of the DNA. Integration of nanomaterials further amplify the response signal which enhances the sensitivity and selectivity of the biosensor [15][16][17]. Biosensors integrated with nanomaterials have shown better stability as well as chemical and electrical properties [18]. Here, graphitic carbon nitride (g-C 3 N 4 ) particles were chosen for the interface of the paper electrodes. g-C 3 N 4 is a semiconducting material which is analogous to graphene with stacked two-dimensional structures [19,20]. The semiconducting 2-D g-C 3 N...

The present report employed nanobroom (NB)-shaped two-dimensional molybdenum diselenide (MoSe2) for the preparation of a sensing matrix for the detection of Salmonella paratyphi. An aptamer specific to salmonella was immobilized onto MoSe2NB-modified fluorine-doped tin oxide via glutaraldehyde cross-linking. Structural and morphological characterizations were performed using UV–vis spectroscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction techniques. Characterizations confirmed the nanobroom morphology and nanosize of the MoSe2 material. Electrochemical studies revealed a good linear detection range of 10–2–10–10 CFU/mL with low detection limit of 1 × 10–10 CFU/mL and with R2 = 0.98. The developed preferable nanobroom-shaped sensing matrix can provide a promising platform for rapid and accurate detection of Salmonella in real samples due to its tremendous stability and sensitivity.