Amine Functionalized Gadolinium Oxide Nanoparticles-Based Electrochemical Immunosensor for Cholera

Herein, we report the synthesis and functionalization of gadolinium oxide nanoparticles (Gd₂O₃ NPs) to fabricate a highly efficient immunosensor for the detection of Vibrio cholera toxin (CT). Gd₂O₃ NPs were produced in a straightforward manner utilizing the microwave irradiation technique using a domestic microwave oven. X-ray diffraction, transmission electron microscopy, and spectroscopic techniques were used to characterize the structural and physical aspects of Gd₂O₃ NPs. The Gd₂O₃ NPs were then functionalized with 3-(Aminopropyl) triethoxysilane (APTES) and electrophoretically deposited onto an ITO-coated glass substrate. The anti-CT monoclonal antibodies were covalently attached to the APTES-Gd₂O₃/ITO electrode via EDC-NHS chemistry, followed by bovine serum albumin (BSA). For CT detection, electrochemical response experiments using BSA/anti-CT/APTES-Gd₂O₃/ITO immunoelectrodes were carried out (5-700 ng mL^-1). The immunoelectrode demonstrated an outstanding electrochemical reaction against CT, with a sensitivity of 8.37 mA ng^-1 mL cm^-2 and a detection limit of 1.48 ng mL^-1.

Blood Oxygen Sensor Using a Boron-Doped Diamond Electrode

The electrochemical behavior of oxygen (O₂) in blood was studied using boron-doped diamond (BDD) electrodes. Cyclic voltammogram of O₂ in a 0.1 M phosphate buffer solution solution containing 1 × 10^-6 M of bovine hemoglobin exhibits a reduction peak at -1.4 V (vs Ag/AgCl). Moreover, the scan rate dependence was investigated to study the reduction reaction mechanism, which was attributable to the reduction of O₂ to H₂O₂ via two electrons. A linear calibration curve was observed in the concentration range of 86.88-314.63 mg L^-1 (R² = 0.99) with a detection limit of 1.0 mg L^-1 (S/B = 3). The analytical performance was better than those with glassy carbon or platinum electrodes as the working electrode. In addition, an application to bovine blood was performed. The O₂ concentration in the blood measured on the BDD electrodes was compared to that measured using an OxyLite Pro fiber-optic oxygen sensor device. Both methods gave similar values of the O₂ concentration in the range of ∼40 to 150 mmHg. This result confirms that BDD electrodes could potentially be used to detect the O₂ concentration in blood.

A reduced graphene oxide-titanium dioxide nanocomposite based electrochemical aptasensor for rapid and sensitive detection of Salmonella enterica

Recent foodborne outbreaks in multiple locations necessitate the continuous development of highly sensitive and specific biosensors that offer rapid detection of foodborne biological hazards. This work focuses on the development of a reduced graphene oxide‑titanium dioxide (rGO-TiO₂) nanocomposite based aptasensor to detect Salmonella enterica serovar Typhimurium. A label-free aptamer was immobilized on a rGO-TiO₂ nanocomposite matrix through electrostatic interactions. The changes in electrical conductivity on the electrode surface were evaluated using electroanalytical methods. DNA aptamer adsorbed on the rGO-TiO₂ surface bound to the bacterial cells at the electrode interface causing a physical barrier inhibiting the electron transfer. This interaction decreased the DPV signal of the electrode proportional to decreasing concentrations of the bacterial cells. The optimized aptasensor exhibited high sensitivity with a wide detection range (10⁸ to 10¹ cfu mL^-1), a low detection limit of 10¹ cfu mL^-1 and good selectivity for Salmonella bacteria. This rGO-TiO₂ aptasensor is an excellent biosensing platform that offers a reliable, rapid and sensitive alternative for foodborne pathogen detection.

Carbon nanotube-based aptasensor for sensitive electrochemical detection of whole-cell Salmonella

In this study, an amino-modified aptasensor using multi-walled carbon nanotubes (MWCNTs)-deposited ITO electrode was prepared and evaluated for the detection of pathogenic Salmonella bacteria. An amino-modified aptamer (ssDNA) which binds selectively to whole-cell Salmonella was immobilised on the COOH-rich MWCNTs to produce the ssDNA/MWCNT/ITO electrode. The morphology of the MWCNT before and after interaction with the aptamers were observed using scanning electron microscopy (SEM). Cyclic voltammetry and electrochemical impedance spectroscopy techniques were used to investigate the electrochemical properties and conductivity of the aptasensor. The results showed that the impedance measured at the ssDNA/MWCNT/ITO electrode surface increased after exposure to Salmonella cells, which indicated successful binding of Salmonella on the aptamer-functionalised surface. The developed ssDNA/MWCNT/ITO aptasensor was stable and maintained linearity when the scan rate was increased from 10 mV s^-1 to 90 mV s^-1. The detection limit of the ssDNA/MWCNT/ITO aptasensor, determined from the sensitivity analysis, was found to be 5.5 × 10¹ cfu mL^-1 and 6.7 × 10¹ cfu mL^-1 for S. Enteritidis and S. Typhimurium, respectively. The specificity test demonstrated that Salmonella bound specifically to the ssDNA/MWCNT/ITO aptasensor surface, when compared with non-Salmonella spp. The prepared aptasensor was successfully applied for the detection of Salmonella in food samples.

Oxalic acid capped iron oxide nanorods as a sensing platform

A label free impedimetric immunosensor has been fabricated using protein bovine serum albumin (BSA) and monoclonal antibodies against Vibrio cholerae (Ab) functionalized oxalic acid (OA) capped iron oxide (Fe3O4) nanorods for V. cholerae detection. The structural and morphological studies of Fe3O4 and OA-Fe3O4, were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and dynamic light scattering (DLS) techniques. The average crystalline size of Fe3O4, OA-Fe3O4 nanorods were obtained as about 29±1 and 39±1nm, respectively. The hydrodynamic radius of nanorods is found as 116nm (OA-Fe3O4) and 77nm (Fe3O4) by DLS measurement. Cytotoxicity of Fe3O4 and OA-Fe3O4 nanorods has been investigated in the presence of human epithelial kidney (HEK) cell line 293 using MTT assay. The cell viability and proliferation studies reveal that the OA-Fe3O4 nanorods facilitate cell growth. The results of electrochemical response studies of the fabricated BSA/Ab/OA-Fe2O3/ITO immunosensor exhibits good linearity in the range of 12.5-500ng mL(-1) with low detection limit of 0.5ng mL(-1), sensitivity 0.1Ωng(-1)ml(-1)cm(-2) and reproducibility more than 11 times.

Highly manufacturable graphene oxide biosensor for sensitive Interleukin-6 detection

Reduced graphene oxide can be used as a sensitive label-free sensor transducer for detection of Interleukin-6 proteins, by overcoming the variable coverage and high electrical resistance, via ethanol Chemical Vapour Deposition (CVD).

Titania nanostructures: a biomedical perspective

A systematic and comprehensive summary of various TNS-based biomedical research with a special emphasis on drug-delivery, tissue engineering, biosensor, and anti-bacterial applications.

A chitosan modified nickel oxide platform for biosensing applications

We present a highly sensitive and selective electrochemical sandwich immunosensor (the analyte is “sandwiched” between two antibodies) based on chitosan modified nickel oxide nanoparticles for the detection of Vibrio cholerae.