M. F. Fatin

HIV-1 Tat biosensor: Current development and trends for early detection strategies.

Human immunodeficiency virus (HIV) has infected almost 35 million people worldwide. Various tests have been developed to detect the presence of HIV during the early stages of the disease in order to reduce the risk of transmission to other humans. The HIV-1 Tat protein is one of the proteins present in HIV that are released abundantly approximately 2-4 weeks after infection. In this review, we have outlined various strategies for detecting the Tat protein, which helps transcribe the virus and enhances replication. Detection strategies presented include immunoassays, biosensors and gene expression, which utilize antibodies or aptamers as common probes to sense the presence of Tat. Alternatively, measuring the levels of gene transcription is a direct method of analysing the HIV gene to confirm the presence of Tat. By detection of the Tat protein, virus transmission can be detected in high-risk individuals in the early stages of the disease to reduce the risk of an HIV pandemic.

Surface functionalization of multiwalled carbon nanotube for biosensor device application

CNT has been widely known for its excellent electrical and thermal conductivities. However, these desirable properties are limited for application due to the inertness of CNT. This work emphasize on a simple and practical method of MWCNT functionalization by sonication in mild acid condition. A mixture of nitric acid and sulfuric acid in ratio of 1:3 were demonstrated as an oxidizing agent to introduce carboxyl functional group on MWCNTs surface. The chemical bonding and surface morphology were examined using FTIR and SEM respectively and indicates a successful functionalization of carboxyl functional group. This work will be further developed for application of functionalized MWCNT for biosensor device.

Oxidation functionalization of multiwalled carbon nanotube by mild acid sonication

Multiwalled carbon nanotube (MWCNT) has excellent properties in thermal and electrical conductivities, high tensile strength and surface area and low mass over volume. However, the usage is still limited due to its inert characteristic. MWCNT surface is hydrophobic and not miscible in most solvents. This work emphasize on simple and practical method of functionalization by sonication in mild acid condition. 6M of Nitric acid and Sulfuric acid mixture (Method I) and 6M of Nitric acid (Method II) were demonstrated as an oxidizing agent to introduce carboxyl functional group on MWCNTs surface. Both type of functionalization has demonstrated carboxyl formation but functionalization in acid mixture was chosen to be used for further study for aptamer immobilization. FTIR and SEM have been used to investigate the binding properties and surface morphology respectively. The functionalization time has also been studied by using dispersability test which resulted in good dispersion after 1 hour of functionalization.

Functionalization of Multi Wall Carbon Nanotubes Using Nitric Acid Oxidation

Functionalized of Multi Wall Carbon Nanotubes (MWCNTs) were demonstrated using the nitric acid (HNO3) oxidation technique in order to get opened caps, removing carbonaceous and metal particles impurities for carboxylic groups (-COOH). The surface morphology and the existence of the carboxyl-group on the MWCNTs were examined using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM), respectively. The carboxylic groups were observed at the peak of 1640.40cm-1 via FTIR and indicate the absorbance intensity of the functionalized MWCNTs is 2.22 A which is higher than raw material. Furthermore, SEM image shows the bundle of structure on the raw MWCNTs signified the Van der Waals interaction between MWCNTs while after functionalized a groovy CNTs wall were observed due to presence of carboxyl group at the defect sites.

The impact of channel doping in junctionless field effect transistor

In this paper, we present the simple approach in study the impact of channel doping on the operation of the junctionless transistor transistor in 25 nm gate lengths through 2D-TCAD Sentaurus simulation tools. We increase the channel doping up to the level of doping source and drain, thus creating the junctionless phenomena between source and drain. The transistor parameters such as threshold voltage, transconductance, subthreshold slope, drain-induced barrier lowering are extracted. The impacts of low and high drain voltages are also considered. The higher the doping concentration the larger drain current can be produced, however the drawback is larger subthreshold slope is also obtained due to wider channel preventing fully-depletion.

Preparation and characterization of MWCNT dispersed in various solutions

In modern technology of biomedical applications, the potential of carbon nanotubes based materials has been widely used in recent years. In this paper, the preparation of the multi wall carbon nanotube (MWCNT) with biocompatibility of these composite are investigated, although many aspects have been studied separately by researchers. We have chosen three different solvents; namely chitosan, Sodium Dodecyl Sulfate (SDS), and isopropyl alcohol (IPA) to mix with MWCNT respectively. This functionalized CNT with carboxylic (COOH) groups were prepared in three different liquid forms and further will be dropped on fabricated Interdigitated electrodes (IDEs) as devices. Scanning electron microscopy (SEM) was used to identify the structures effect of synthesized MWCNT in different solvents. The conductivities show the ability of chitosan and SDS to be used as a solvent in order to synthesis MWCNTs and further will be used as a biosensor.

Integrated titanium dioxide (TiO2) nanoparticles on interdigitated device electrodes (IDEs) for pH analysis

Titanium dioxide (TiO2) nanoparticles based Interdigitated Device Electrodes (IDEs) Nanobiosensor device was developed for intracellular biochemical detection. Fabrication and characterization of pH sensors using IDE nanocoated with TiO2 was studied in this paper. In this paper, a preliminary assessment of this intracellular sensor with electrical measurement under different pH levels. 3-aminopropyltriethoxysilane (APTES) was used to enhance the sensitivity of titanium dioxide layer as well as able to provide surface modification by undergoing protonation and deprotonation process. Different types of pH solution provide different resistivity and conductivity towards the surface. Base solution has the higher current compared to an acid solution. Amine and oxide functionalized TiO2 based IDE exhibit pH-dependent could be understood in terms of the change in surface charge during protonation and deprotonation. The simple fabrication process, high sensitivity, and fast response of the TiO2 based IDEs facilita...

Surface morphology of titanium dioxide (TiO2) nanoparticles on aluminum interdigitated device electrodes (IDEs)

Titanium dioxide (TiO2) nanoparticles based Interdigitated Device Electrodes (IDEs) Nanobiosensor device was developed for intracellular biochemical detection. Fabrication and characterization of Scanning Electron Microscopy (SEM) using IDE nanocoated with TiO2 was studied in this paper. SEM analysis was carried out at 10 kV acceleration volatege and a 9.8 mA emission current to compare IDE with and without TiO2 on the surface area. The simple fabrication process, high sensitivity, and fast response of the TiO2 based IDEs facilitate their applications in a wide range of areas. The small size of semiconductor TiO2 based IDE for sensitive, label-free, real time detection of a wide range of biological species could be explored in vivo diagnostics and array-based screening.

Fabrication and characterization on reduced graphene oxide field effect transistor (RGOFET) based biosensor

The fabrication and characterization on reduced graphene oxide field effect transistor (RGO-FET) were demonstrated using a spray deposition method for biological sensing device purpose. A spray method is a fast, low-cost and simple technique to deposit graphene and the most promising technology due to ideal coating on variety of substrates and high production speed. The fabrication method was demonstrated for developing a label free aptamer reduced graphene oxide field effect transistor biosensor. Reduced graphene oxide (RGO) was obtained by heating on hot plate fixed at various temperatures of 100, 200 and 300°C, respectively. The surface morphology of RGO were examined via atomic force microscopy to observed the temperature effect of produced RGO. The electrical measurement verify the performance of electrical conducting RGO-FET at temperature 300°C is better as compared to other temperature due to the removal of oxygen groups in GO. Thus, reduced graphene oxide was a promising material for biosensor application.

Fabrication and electrical characterization of graphene oxide as transducing channel for biosensor application

In this paper, we present the fabrication and electrical characterization of field-effect transistor-based sensor with integrated graphene oxide (GO) on channel between source and drain. We aim to demonstrate the optimum condition in electrical performance for field-effect transistor-based biosensor device. Graphene oxide prepared by using modified hummers method was deposited on the channel with different amount to act as amplification layer on the FET. The structural properties of GO were examined using photoluminescence (PL). A 3D surface profilometer were used to observe the surface morphology of GO-FET. Multi-graphene layer on the FET channel result in increasing the current flow in the device and make it more sensitive to be used as biosensor.