Xenia Meshik

Detection of Interferon gamma using graphene and aptamer based FET-like electrochemical biosensor

One of the primary goals in the scientific community is the specific detection of proteins for the medical diagnostics and biomedical applications. Interferon-gamma (IFN-γ) is associated with the tuberculosis susceptibility, which is one of the major health problems globally. We have therefore developed a DNA aptamer-based electrochemical biosensor that is used for the detection of IFN-γ with high selectivity and sensitivity. A graphene monolayer-based FET-like structure is incorporated on a PDMS substrate with the IFN-γ aptamer attached to graphene. Addition of target molecule induces a change in the charge distribution in the electrolyte, resulting in increase in electron transfer efficiency that was actively sensed by monitoring the change in current from the device. Change in current appears to be highly sensitive to the IFN-γ concentrations ranging from nanomolar (nM) to micromolar (μM) range. The detection limit of our IFN-γ electrochemical biosensor is found to be 83 pM. Immobilization of aptamer on graphene surface is verified using unique structural approach by Atomic Force Microscopy. Such simple and sensitive electrochemical biosensor has potential applications in infectious disease monitoring, immunology and cancer research in the future.

Graphene- and aptamer-based electrochemical biosensor

This study investigated the effectiveness of a graphene- and aptamer-based field-effect-transistor-like (FET-like) sensor in detecting lead and potassium ions. The sensor consists of a graphene-covered Si/SiO2 wafer with thrombin binding aptamer (TBA) attached to the graphene layer and terminated by a methylene blue (MB) molecule. K(+) and Pb(2+) both bind to TBA and cause a conformational change, which results in MB moving closer to the graphene surface and donating an electron. Thus, the abundance of K(+) and Pb(2+) can be determined by monitoring the current across the source and drain channel. Device transfer curves were obtained with ambipolar field effect observed. Current readings were taken for K(+) concentrations of 100 μM to 50 mM and Pb(2+) concentrations of 10 μM to 10 mM. As expected, I d decreased as ion concentration increased. In addition, there was a negative shift in V Dirac in response to increased ion concentration.

A Graphene and Aptamer Based Liquid Gated FET-Like Electrochemical Biosensor to Detect Adenosine Triphosphate

Here we report successful demonstration of a FET-like electrochemical nano-biosensor to accurately detect ultralow concentrations of adenosine triphosphate. As a 2D material, graphene is a promising candidate due to its large surface area, biocompatibility, and demonstrated surface binding chemistries and has been employed as the conducting channel. A short 20-base DNA aptamer is used as the sensing element to ensure that the interaction between the analyte and the aptamer occurs within the Debye length of the electrolyte (PBS). Significant increase in the drain current with progressive addition of ATP is observed whereas for control experiments, no distinct change in the drain current occurs. The sensor is found to be highly sensitive in the nanomolar (nM) to micromolar ( μM) range with a high sensitivity of 2.55 μA (mM) -1, a detection limit as low as 10 pM, and it has potential application in medical and biological settings to detect low traces of ATP. This simplistic design strategy can be further extended to efficiently detect a broad range of other target analytes.

Design and Applications of Nanomaterial-Based and Biomolecule-Based Nanodevices and Nanosensors

This review will highlight recent research underlying the design of novel nanodevices and nanosensors that incorporate graphene, nanodots, nanowires, and biomolecules including DNA aptamers and peptides. The emphasis is on models and theory that guide the design of these nanodevices and nanosensors. In selected cases, research designed to test the usefulness of these designs is highlighted in this chapter.

Submillimolar Detection of Adenosine Monophosphate Using Graphene-Based Electrochemical Aptasensor

In this paper, we present a successful demonstration of a graphene-based field-effect-transistor-like electrochemical nanobiosensor to accurately detect ultralow concentrations of adenosine monophosphate (AMP). Graphene being a two-dimensional material is a suitable option as a sensing element due to its biocompatibility and large surface area. It has also demonstrated surface binding chemistries as well as its ability to serve as a conducting channel. A short 20-base deoxyribonucleic acid (DNA) aptamer is used as the sensing element to ensure that the interaction between the analyte and the aptamer occurs within the Debye length of the electrolyte. The sensor is found to be nonlinear in nature and sensitive in the picomolar (pM) and nanomolar (nM) concentrations of AMP. The linear region of operation is found to be 1 nM–100 μM and percentage change in drain current in this concentration region is calculated as

Electrostatic force analysis, optical measurements, and structural characterization of zinc oxide colloidal quantum dots synthesized by sol-gel method

{\text{1.56}}{\boldsymbol{\% }}/{\boldsymbol{decade}}

Modulation of voltage-gated conductances of retinal horizontal cells by UV-excited TiO2 nanoparticles

. A minimum concentration of 10 pM of AMP has been detected using this type of sensor.

Screening effect on electric field produced by spontaneous polarization in ZnO quantum dot in electrolyte

ZnO quantum dots (QDs) are used in a variety of applications due to several desirable characteristics, including a wide band gap, luminescence, and biocompatibility. Wurtzite ZnO QDs also exhibit a spontaneous polarization along the growth axis, leading to large electric fields. In this work, ZnO QDs around 7 nm in diameter are synthesized using the sol-gel method. Their size and structure are confirmed using photoluminescence, Raman spectroscopy, atomic force microscopy, and transmission electron microscopy. Additionally, electrostatic force microscopy (EFM) is used to measure the amplitude change in the probe which is associated with the electric field produced by ZnO immobilized by layer-by-layer synthesis technique. The measured electrostatic field of 108 V/m is comparable to theoretically predicted value. Additionally, the strength of the electrostatic field is shown to depend on the orientation of the QDs c-axis. These results demonstrate a unique technique of quantifying ZnOs electric force using...

Surface-enhanced Raman spectroscopy as a tool for characterizing nanostructures containing molecular components

This study examines the ability of optically-excited titanium dioxide nanoparticles to influence voltage-gated ion channels in retinal horizontal cells. Voltage clamp recordings were obtained in the presence and absence of TiO2 and ultraviolet laser excitation. Significant current changes were observed in response to UV light, particularly in the -40 mV to +40 mV region where voltage-gated Na+ and K+ channels have the highest conductance. Cells in proximity to UV-excited TiO2 exhibited a left-shift in the current-voltage relation of around 10 mV in the activation of Na+ currents. These trends were not observed in control experiments where cells were excited with UV light without being exposed to TiO2. Electrostatic force microscopy confirmed that electric fields can be induced in TiO2 with UV light. Simulations using the Hodgkin-Huxley model yielded results which agreed with the experimental data and showed the I-V characteristics of individual ion channels in the presence of UV-excited TiO2.

Graphene oxide and DNA aptamer based sub-nanomolar potassium detecting optical nanosensor

In this paper, the calculation of the strength of the electrostatic field produced by ZnO quantum dots due to the spontaneous polarization in a physiological electrolyte and its application on retinal horizontal cells are presented.