One pot fabrication of diamino naphthalene -AuNPs decorated graphene nanoplatform for the MRSA detection in the biological sample.

Early monitoring of MRSA can effectively mitigate the disease risk by using Penicillin-binding protein 2a (PbP2a) biomarker. Diamino naphthalene-AuNPs decorated graphene (AuNPsGO-DN) nanocomposite was synthesized for a rapid and sensitive immunosensor detecting PbP2a. The synthesized AuNPsGO-DN nanocomposites were characterized by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (SEM-EDX), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, and X-ray diffraction spectroscopy (XRD). Electrochemical characterization done with cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrical impedance spectroscopy (EIS) techniques. Anti-PbP2a monoclonal antibodies immobilized at AuNPsGO-DN/GCE via covalent bonding. AuNPs enhanced the electrode surface area and the antibodies' loading. Mercaptopropionic acid (MPA) was a linker between the AuNPs and antibodies, orientated the antibodies as opposite to the PbP2a antigen, and improved the sensitivity and specificity. The antiPbP2a/MPA/AuNPsGO-DN/GCE electrode displayed sensitive and selective detection towards the PbP2a antigen in phosphate buffer saline (PBS pH 7.4). The broad linear range from 0.01 to 8000 pg/mL was obtained with LOD of 0.154 pg/mL and 0.0239 pg/mL, respectively. A label-free, simple, and sensitive immunosensor was developed with a 98-106 % recovery rate in spiked biological samples. It shows the potential applicability of the developed immunoelectrode.

Rapid and label-free A2 peptide epitope decorated CoFe2O4-C60 nanocomposite-based electrochemical immunosensor for detecting Visceral Leishmaniasis.

Diagnosis of Visceral Leishmaniasis is challenging due to the shared clinical features with malaria, typhoid, and tuberculosis. A CoFe2O4-C60 nanocomposite-based immunosensor decorated with a sensitive A2 peptide antigen was fabricated to detect anti-A2 antibodies for application in visceral leishmaniasis diagnosis. The flame-synthesised nanocomposite was characterised using Fourier Transform Infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), Raman spectroscopy and electrochemical impedance spectroscopy (EIS) techniques. N terminated specific A2 peptide epitope antigen (NH2-QSVGPLSVGP-OH) was synthesised and characterised by high-performance liquid chromatography (HPLC) and liquid chromatography-mass spectroscopy (LC-MS). Using EDC/NHS, A2 peptide antigen (Apg) was immobilised on the CoFe2O4-C60-modified electrode. The performance of the immunosensor, Apg-CoFe2O4-C60NP/GCE, was evaluated by testing its ability to detect varying concentrations of anti-A2 antibody solution in PBS and spiked serum with 1 mM [Fe(CN)6]3-/4- in 0.01 M PBS (pH 7.4) as supporting electrolyte. using differential pulse voltammetry. The immunosensor showed excellent reproducibility and a linear range of 10-10-10-1 µg/mL, with an experimental detection limit of 30.34 fg/mL. These results suggest that the fabricated sensor has great potential as a tool for diagnosing visceral leishmaniasis.

Rapid sensing ofTilletia indica - Teliospore in wheat extractby apiezoelectric label free immunosensor.

'Tilletia indica', a fungal pathogen causes Karnal bunt disease in wheat. It has been renowned as a quarantine pest in more than 50 countries, therefore, urged a threat to wheat in the international market. To date, conventional methods employed to detect the disease involve the tentative identification of spores (teliospores) based on morphology. For effective and specific disease control, it is essential to get the specific protein of the analyte (teliospore) to target. In present study, a label-free immunosensor has been developed to detect Karnal bunt disease. A specifically synthesized anti-teliosporic monoclonal antibody (mAb) was immobilized on a self-assembled monolayer of 11-mercaptoundecanoic acid (11-MUA) to detect teliospore. All modified electrodes were morphologically characterized by scanning electron microscopy (SEM), atomic force microscopy(AFM), Fourier transform infra-red spectroscopy (FT-IR) techniques and analytically characterized by quartz crystal microbalance (QCM) and cyclic voltammetry (CV). The linearity range was 19 pg mL-1-10 ng mL-1, while the detection limit (LOD) was 4.4 pg mL-1 and 12.5 pg mL-1, respectively. The stability, reproducibility, and repeatability of the immunoelectrode was examined by CV, and found stable upto 18 days with negligible variation. The binding affinity (association constant (Ka)) of the developed immunoelectrode was 1.9 × 10-2 ng mL-1. The real sample has been tested in spiked wheat samples and found about 95-103 % recovery with 2.8-4.4 % relative error.

Recent progress in electrochemical sensors for detection and quantification of malaria.

Malaria is still a major disease in sub-Saharan Africa and South-East Asia. This is despite different interventions by the World Health Organization (WHO), such as insecticide-treated mosquito net, antimalarial drugs, indoor residual spraying, and rapid diagnostic tools. In 2018, the mortality rate due to malaria was estimated to be 405 000, with children under five years accounting for 67% of all malaria deaths. Malaria can be prevented and treated using different strategies as recommended by WHO. However, the lack of rapid diagnostic tools with good selectivity and sensitivity is still a challenge. Therefore there is a need to develop rapid, low-cost, and portable analytical methods for quantifying malaria. This review focuses on the role of malaria biomarkers (Plasmodium falciparum Lactate Dehydrogenase (PfLDH), Plasmodium aldolase, Plasmodium falciparum Histidine-Rich Protein 2 (PfHRP2), Plasmodium falciparum Glutamate dehydrogenase (PfGDH), and Hemozoin) in diagnosis. Recent developments in nanomaterial-based electrochemical and colorimetric biosensors for malaria diagnosis are discussed. Finally, the review concludes with closing remarks and future perspectives of electrochemical biosensors.

One-pot synthesis of ß-cyclodextrin modified silver nanoparticles for highly sensitive detection of ciprofloxacin.

This study emphases on electrochemical detection of ciprofloxacin in sheep serum and runoff water using silver nanoparticle modified ß-cyclodextrin (Ag-ß-CD) composite. The Ag-ß-CD composite was synthesized via a hydrothermal route, which resulted in a high product yield. Morphological and spectral characterizations of the Ag-ß-CD composite were carried out. The Ag-ß-CD composite was used to detect ciprofloxacin by employing differential pulse voltammetry (DPV) and cyclic voltammetry (CV). The Ag-ß-CD modified electrode displayed excellent specificity towards the electro-oxidation of ciprofloxacin. Further, the sensor gave the best response towards the electro-oxidation of ciprofloxacin near the human physiological pH of 7.5. A linear response was obtained between the concentration range of 0.1 nM to 50 nM and the limit of detection (LOD) at 0.028 nM with high sensitivity and selectivity towards ciprofloxacin oxidation. The current work has a rationally synthesized and characterized nanocomposite with a very high potential for rapid and sensitive detection of ciprofloxacin in spiked sheep blood serum and domestic runoff water samples. High sensitivity and low LOD results illustrate good practicability for the detection of ciprofloxacin in such samples in the near future.

A poly(acrylic acid)-modified copper-organic framework for electrochemical determination of vancomycin.

A copper(II) benzene-1,3,5-tricarboxylate (BTC) metal-organic framework (MOF) was modified with poly(acrylic acid) (PAA) and then used in an electrochemical sensor for vancomycin. The MOF, synthesized via a single-pot method, has enhanced solubility and dispersibility in water as compared to HKUST-1 but without compromising its crystallinity and porosity. The MOF was placed on a glassy carbon electrode (GCE) where it shows enhanced electrocatalytic properties. This is assumed to be due to the presence of the poly(acrylic acid) that forms a network between various HKUST-1 crystals through dimer formation between the carboxy groups of BTC and PAA. This also led to better dispersion of the MOF and to improved interaction between MOF and vancomycin. The structural, spectral and electrochemical properties of the MOFs and their vancomycin complexes was characterized. The modified GCE is shown to be a viable tool for electrochemical determination (best at a working potential of 784 mV vs. Ag/AgCl) of the antibiotic vancomycin in spiked urine and serum samples. Response is linear in the 1-500 nM vancomycin concentration range, and the detection limit is 1 nM, with a relative standard deviation of ±4.3%. Graphical abstractSchematic representation of a method for determination of vancomycin. Poly(acrylic acid) modified HKUST-1 (P-HKUST-1) forms a complex with vancomycin [Van-P-HKUST-1] which is coated over glassy carbon electrode (GCE). The decrease in peak current is recorded as response to vancomycin via cyclic voltammetry.

Bi-enzyme functionalized electro-chemically reduced transparent graphene oxide platform for triglyceride detection.

Recently, increased attention has been drawn to application of graphene and its derivatives for construction of biosensors, since they can be used to rapidly detect the presence of bio-analytes. Present paper establishes the preparation of a unique transducer which relies on toluidine blue (TB), absorbed by electrochemically reduced graphene oxide (ERGO) transparent thin film onto the surface of the indium tin-oxide (ITO) glass electrode. The proposed TB/ERGO/ITO electrode shows excellent reversible electro-chemical properties. The novel platform has been explored to fabricate a triglyceride (TG) biosensor via co-immobilizing of lipase (LIP) and glycerol dehydrogenase (GDH) onto TB/ERGO/ITO electrode surface. The fabricated bioelectrode (LIP-GDH/TB/ERGO/ITO) directly oxidizes glycerol (produced by catalytic hydrolysis of tributyrin acting as a model TG) in the presence of GDH. The developed bioelectrode replaces unstable biological irreversible redox mediators NAD+/NADH, involved in the triglyceride breakdown reaction. NADH causes fouling on the bioelectrode surface in bi-enzymatic estimation of TG and reduces the shelf-life of biosensor. Electrochemical response studies carried out using cyclic voltammetry reveal that the fabricated electrode can detect tributyrin in the range of 50-400 mg dL-1 with high sensitivity of 29 pA mg-1 dL, low response time of 12 s, long-term stability and a low apparent Michaelis-Menten constant (Kappm) of 0.18 mM, indicating high enzyme affinity of LIP-GDH/TB/ERGO/ITO bioelectrode towards tributyrin. Furthermore, this modified bioelectrode has been explored for estimation of TG with negligible interference in human serum samples. The proposed bi-enzymatic bioelectrode for TG analysis offers an efficient and novel interface for application of graphene and its derivatives in the field of bioelectronic devices.

Recent advances in mycotoxins detection.

Mycotoxins contamination in both food and feed is inevitable. Mycotoxin toxicity in foodstuff can occur at very low concentrations necessitating early availability of sensitive and reliable methods for their detection. The present research thrust is towards the development of a user friendly biosensor for mycotoxin detection at both academic and industrial levels to replace conventional expensive chromatographic and ELISA techniques. This review critically analyzes the recent research trend towards the construction of immunosensor, aptasensor, enzymatic sensors and others for mycotoxin detection with a reference to label and label free methods, synthesis of new materials including nano dimension, and transuding techniques. Technological aspects in the development of biosensors for mycotoxin detection, current challenges and future prospects are also included to provide a overview and suggestions for future research directions.