An enhanced electrochemical performance of in milk, pigeon meat and eggs samples using se nanorods capped with Co3O4 nanoflowers decorated on graphene oxide.

In this work, we report a novel preparation of selenium nanorods (Se) doped cobalt oxide (Co3O4) nanoflowers encapsulated with graphene oxide (GO) nanocomposite (NC). Se nanorods were successfully decorated on Co3O4 nanoflowers and an increase in electrical conductivity was observed in Se-Co3O4@GO-NC. The as-prepared Se-Co3O4@GO-NC was utilized as an effective nanocomposite for the electrochemical detection of dimetridazole (DMZ) for the first time in the field of electrochemical sensors. Se-Co3O4@GO-NC modified glassy carbon electrode (GCE) which showed an excellent cathodic current response (17.6 µA) at the lower potential at -0.7314 V upon DMZ sensing. With the various optimized conditions, Se-Co3O4@GO-NC based electrochemical sensor displayed a lengthy linear range of 0.02-83.72 µM, limit of detection 3.4 nM and sensitivity of 1.898 µA.µM-1. cm-2 for DMZ detection. In addition, Se-Co3O4@GO-NC revealed fabulous catalytic reduction activity for DMZ, when compared to GO and Se-Co3O4 modified GCE. Additionally, Se-Co3O4@GO-NC is applied in real sample analysis of pigeon egg, milk and pigeon meat. The results illustrated that Se-Co3O4@GO-NC can be a promising nanocomposite for the electrocatalytic reduction of DMZ in clinical samples in biomedical field.

Microfluidic electrochemical immunosensor for the determination of cystatin C in human serum.

The fabrication of a nanointerfaced electrochemical immunosensor is described for the rapid determination of cystatin C, a biomarker that is elevated in diabetic retinopathy. A dispersion of graphene oxide-chitosan (GO-Chit) nanocomposite was used to modify the carbon working electrode, allowing for a high conjugation of anti-cystatin C antibody. This modified sensor was characterized both morphologically and electrochemically, and the sensor performance was evaluated towards selective quantification of cystatin C in simulated as well as serum samples using cyclic voltammetry and differential pulse voltammetry. The sensor was able to detect cystatin C in the concentration range1 - 10 mg/L with a detection limit of 0.0078 mg/L. The preparation time of the sensor was 420 s, which was faster than that of conventional ELISA and other electrochemical sensors reported in literature. The clinical applicability of the proposed electrochemical biosensor was demonstrated through quantification of cystatin C in human serum samples and identification of diabetic retinopathy. A cutoff value of 1.2 mg/L of cystatin C was used beyond which the samples were classified as positive for diabetic retinopathy. Two different working electrodes, namely a glassy carbon electrode (GCE) and paper electrodes, were used in the study. The working potential was set to 0.25 V vs. Ag/AgCl for experiments with the GCE and 0.15 V for the paper electrodes. The prediction was validated by clinical diagnosis wherein the prediction accuracy of the sensor exceeded 85%. The sensor platform was translated onto a paper substrate and characterized for achieving an optimum sensing performance. This work is the first attempt to employ an electrochemical cystatin C sensor for the diagnosis of diabetic retinopathy from serum samples. Graphical abstract.

Metabolic Syndrome-An Emerging Constellation of Risk Factors: Electrochemical Detection Strategies.

Metabolic syndrome is a condition that results from dysfunction of different metabolic pathways leading to increased risk of disorders such as hyperglycemia, atherosclerosis, cardiovascular diseases, cancer, neurodegenerative disorders etc. As this condition cannot be diagnosed based on a single marker, multiple markers need to be detected and quantified to assess the risk facing an individual of metabolic syndrome. In this context, chemical- and bio-sensors capable of detecting multiple analytes may provide an appropriate diagnostic strategy. Research in this field has resulted in the evolution of sensors from the first generation to a fourth generation of 'smart' sensors. A shift in the sensing paradigm involving the sensing element and transduction strategy has also resulted in remarkable advancements in biomedical diagnostics particularly in terms of higher sensitivity and selectivity towards analyte molecule and rapid response time. This review encapsulates the significant advancements reported so far in the field of sensors developed for biomarkers of metabolic syndrome.

An Elegant Analysis of White Spot Syndrome Virus Using a Graphene Oxide/Methylene Blue based Electrochemical Immunosensor Platform.

White spot syndrome virus (WSSV) is a major devastating virus in aquaculture industry. A sensitive and selective diagnostic method for WSSV is a pressing need for the early detection and protection of the aquaculture farms. Herein, we first report, a simple electrochemical immunosensor based on methylene blue dye (MB) immobilized graphene oxide modified glassy carbon electrode (GCE/GO@MB) for selective, quick (35 ± 5 mins) and raw sample analysis of WSSV. The immunosensor was prepared by sequential modification of primary antibody, blocking agent (bovine serum album), antigen (as vp28 protein), secondary antibody coupled with horseradish peroxidase (Ab2-HRP) on the GCE/GO@MB. The modified electrode showed a well-defined redox peak at an equilibrium potential (E1/2), -0.4 V vs Ag/AgCl and mediated H2O2 reduction reaction without any false positive result and dissolved oxygen interferences in pH 7 phosphate buffer solution. Under an optimal condition, constructed calibration plot was linear in a range of 1.36 × 10-3 to 1.36 × 107 copies µL-1 of vp28. It is about four orders higher sensitive than that of the values observed with polymerase chain reaction (PCR) and western blot based WSSV detection techniques. Direct electrochemical immunosensing of WSSV in raw tissue samples were successfully demonstrated as a real sample system.