Enzyme-based sensing on nanohybrid film coated over FTO electrode for highly sensitive detection of antibiotics.

Cefepime and Meropenem are the new class of antibiotics, which are particularly used as last potent defender or the antibiotics of the last resort against multi-resistant bacterial species. In this paper, an impedance-based electrochemical biosensor was fabricated for identifying antibiotics of last resort in the forensic samples including gastric lavage and other body fluids. The sensor was developed using platinum nanoparticles (PtNPs) and electrodeposited zinc oxide- zinc hexacyanoferrate hybrid film (ZnO/ZnHCF) on the surface of a fluorine-doped glass electrode (FTO). Further, penicillinase was immobilized onto the modified electrode using penicillinase enzyme. The developed biosensor exhibits a good analytical response for the detection of antibiotics evaluated using electrochemistry studies. The linear response of the fabricated electrode was observed from 0.1 to 750 µM and the electrode limit of detection (LOD) was observed as 0.1 µM. The sensor confirms good accuracy, is highly selective, and sensitive for the target. While storing the modified electrode at 4 °C, the stability of biosensor was evaluated for 45 days, and activity loss of 30-40% was observed. The highly sensitive interface of Penicillinase@CHIT/PtNP-ZnO/ZnHCF/FTO electrode shows a promising future in forensic studies.

Nanohybrid-based immunosensor prepared for Helicobacter pylori BabA antigen detection through immobilized antibody assembly with @ Pdnano/rGO/PEDOT sensing platform.

The gastric colonization of human hosts by Helicobacter pylori (H. pylori) increases the risk of developing gastritis, ulcers and gastric cancer. To detect H. pylori, a nanohybrid-based BabA immunosensor is developed herein. BabA is an outer membrane protein and one of the major virulence factors of H. pylori. To design the immunosensor, an Au electrode is loaded with palladium nanoparticles (Pdnano) by electrodeposition to generate reduced graphene oxide (rGO)/poly(3,4-ethylenedioxythiophene) (PEDOT). The immobilization of these nanostructured materials imparts a large surface area and electroconductivity to bio-immune-sensing molecules (here, the BabA antigen and antibodies). After optimization, the fabricated immunosensor has the ability to detect antigens (H. pylori) in a linear range from 0.2 to 20 ng/mL with a low LOD (0.2 ng/mL). The developed immunosensor is highly specific, sensitive and reproducible. Additionally, in silico methods were employed to better understand the hybrid nanomaterials of the fabricated Pdnano/rGO/PEDOT/Au electrode. Simulations performed by molecular docking, and Metropolis Monte Carlo adsorption studies were conducted. The results revealed that the hybrid nanomaterials exhibit a stable antigen-antibody complex of BabA, yielding the lowest binding energy in relation to the electrode materials, emphasizing the functionality of the constructed electrodes in the electrochemical immunosensor.

Triple-nanostructuring-based noninvasive electro-immune sensing of CagA toxin for Helicobacter pylori detection.

BACKGROUND: Helicobacter pylori (H pylori) is gram-negative, spiral, and microaerophilic bacteria which can survive in ~2%-10% oxygen level. It was reported to populate in human gastric mucosa and leads to gastric cancer without any age or gender difference. MATERIALS AND METHODS: In this study, we are targeting label-free electrochemical immunosensor development for rapid H pylori detection after covalently immobilizing the antibody (CagA) over the nanomaterials modified Au electrode. Titanium oxide nanoparticles (TiO2 NPs), carboxylated multi-walled carbon nanotubes (c-MWCNT), and conducting polymer polyindole carboxylic acid (Pin5COOH) composites (TiO2 NPs/c-MWCNT/Pin5COOH) were synthesized and further utilized in immunosensor development as an electrochemical interface onto Au electrode. The stepwise modifications of CagAantibody/TiO2 NPs/c-MWNCT/Pin5COOH/Au electrode were electrochemically studied. RESULTS: Possessing the unique features of advanced materials, the proposed immunosensor reported low sensing limit of 0.1 ng/mL in dynamic linear range of 0.1-8.0 ng/mL with higher stability and reproducibility. Furthermore, developed sensor-based determination of H pylori in five human stool specimens has shown good results with suitable accuracy. CONCLUSIONS: This work lays strong foundation toward developing nanotechnology-enabled electrochemical sensor for ultrasensitive and early detection of H pylori in noninvasively collected clinical samples.

Synergistic effect of 2D material coated Pt nanoparticles with PEDOT polymer on electrode surface interface for a sensitive label free Helicobacter pylori CagA(Ag-Ab) immunosensing.

Helicobacter pylori (H. pylori) immunosensor based on platinum nanoparticles/poly(3,4-ethylenedioxythiophene)/reduced graphene oxide (Ptnano/PEDOT/red-GOx) modified gold electrode (Au-ET) was stepwise fabricated for the detection of cytotoxin-associated gene A antibody (CagA antibody). H. pylori is a microaerophillic and a Gram-negative bacteria that causes gastric ulcer leading eventually to adenocarcinoma (gastric cancer) in the later stage. H. pylori colonizes inner lining of human stomach. The developed diagnostic sensing interface would allow H. pylori (stomach infection) detection in early stage and would be a great contribution in clinical laboratories. In order to fabricate the immunosensor, CagA antigen was immobilized over the Ptnano/PEDOT/red-GOx modified Au-ET. Afterwards, the modified electrode was used for immuno-sensing of H. pylori specific Cag A antibodies in serum. At lower voltage the modified Ptnano/PEDOT/red-GOx/Au-ET shows an amplified sensing at the interface that makes the sensor more sensitive and specific. CagA is a virulence factor produced by H. pylori was determined by sudden decrease in the current. The laboratory synthesized nano composites were characterised by Scanning Electron Microscopy (SEM) and Atomic force microscopy (AFM) studies. The sensor had excellent linear range of 0.1 ng/ml to 30 ng/ml by limiting the detection range up to 0.1 ng/ml. Moreover, the novel immunosensor formed had good accuracy, precision and reliability. The immunosensor also showed an excellent storage stability by retaining 60-70% of its initial activity until 60 days kept at 4 °C. Highly sensitive interface of CagA antigen@Ptnano/PEDOT/red-GOx/Au-ET shows a promising future for H. pylori detection in diagnosis of stomach ulcer and stomach cancer.

Zinc Oxide Tetrapods Based Biohybrid Interface for Voltammetric Sensing of Helicobacter pylori.

Helicobacter pylori is a Gram-negative, spiral shaped, microaerophilic bacteria that colonizes human gastric mucosa and causes various gastric diseases. In this work, the utilization of ion irradiated zinc oxide tetrapods (ZnO-T) based biohybrid interface accentuates the development of an electrochemical immunosensor for the fast and sensitive detection of H. pylori. After coating of (ZnO-T) over the surface of screen printed electrode (SP-AuE) through electrodeposition, the ZnO-T/SP-AuE was irradiated with N2+ ion of energy 100 keV. The ion irradiation significantly enhances the conductivity of ZnO-T coated SP-AuE. The revamped SP-AuE is further used for establishing an immunosensor interface based upon immobilization of the CagA antigen on ZnO-T electrodeposited over the surface of SP-AuE. The sensing interface demonstrated good linearity (0.2 ng/mL to 50 ng/mL) and limit of detection (0.2 ng/mL). The ion beam irradiated ZnO-T based immunosensor showed significantly high conductivity and enhanced the analytical properties of the working electrode in terms of the sensitivity, detection limit, and response time. A study on the comparison of irradiated and pristine electrode is performed for amperometric sensing of H. pylori. In addition, the significance of work conducted on ion irradiated ZnO-T based interfaces provides a basis of further development of electrochemical immunosensors.

Construction of an amperometric glycated hemoglobin biosensor based on Au-Pt bimetallic nanoparticles and poly (indole-5-carboxylic acid) modified Au electrode.

The glucose level measurement in the diabetic patient plays a vital role in identification of the treatments going on and it also provides the control over the diabetics. A new electrochemical sensing device was constructed for determination of glycated hemoglobin (HbA1c) in whole blood samples. Fructosyl amine oxidase (FAO) was bioconjugated onto hybrid nanocomposite i.e., gold nanoparticles-platinum nanoparticles (AuNPs-PtNPs) and poly indole-5-carboxylic acid (PIN5COOH), deposited electrochemically on gold electrode. Bimetallic nanoparticles not only show their individual properties but also provides the synergistic effect between the two noble metal nanoparticles. AuNPs-PtNPs shown as an amplified sensing interface at lower voltage which makes the sensor more sensitive and specific. The FAO/AuNPs-PtNPs onto PIN5COOH/Au electrode shows a promising future in diagnosis of HbA1c and diabetes management. The novel sensor formed has good accuracy, selectivity, sensitivity, precision and reliability. In addition to these, it showed good storage stability and retained 50% of its initial activity within 12 weeks at 4°C.

Detection of glycated hemoglobin with voltammetric sensing amplified by 3D-structured nanocomposites.

Glycated hemoglobin (HbA1c), a marker for glycine level in blood, while detecting over a long period of time (up to 2-3 months) shows consistency. Therefore, HbA1c has been mostly used and indeed an established test for monitoring the glycemic control in persons suffering from diabetes. 3D-structured reduced graphene oxide (rGO), multiwalled carbon nanotubes (MWCNT) and platinum nanoparticles (PtNPs) composite (PtNPs/rGO-MWCNT) were synthesized and used as interface for the development of an electrochemical HbA1c biosensor. The network structure of rGO-MWCNT nanocomposite provides more active sites for Pt deposition and the synergistic effect of rGO, MWCNTs and PtNPs significantly improved the electrochemical performance of the working electrode. The structure of PtNPs/rGO-MWCNT nanocomposite was characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance study (EIS). This biosensor exhibited a response time of less than 3s, a wide linear concentration range of 0.05-1000µM with detection limit of 0.1µM, good repeatability and satisfactory reproducibility. The biosensor retained 50% of its initial response after 12 weeks at 25°C. The proposed biosensor was successfully applied for the determination of HbA1c concentration in human blood samples with recoveries between 93.7 and 98.3%.