Papers by Keyword: Biosensor

Abstract: Herein, in order to detect hydroquinone (HQ) and catechol (CC) simultaneously, an electrochemical sensor with good selectivity and sensitivity was developed. It is constructed by electrodeposition of carbon nanodots (CDs) on the surface of multi-walled carbon nanotubes (MWNTs) doped glassy carbon electrode. First, the experimental parameter was optimized. The electrochemical behavior was then evaluated by electrochemical impedance spectroscopy and cyclic voltammetry. The linear range for HQ and CC was 0.1-200 μM, and the detection limit was 0.03 μM. Incorporated the large surface area and fast charge transfer of MWNTs and CDs with electrodeposition technology's stability, high excellent selectivity, sensitivity, stability and good reproducibility was exhibited by the fabricated sensor. Furthermore, the electrode was successfully used to determine the concentration of HQ and CC in tap water, and thus exhibited potential applications environment monitoring.

Abstract: Materials modification with surface functional group for bioactive film or sensor surface is important in many applications. A suitable surface for each system can be shown high efficiency of detection. In this work, two different surfaces via covalent binding are created on gold substrate for finding the suitable surface in medical applications. The liver cancer biomarker, alpha-fetoprotein (AFP) was detected on two surfaces; one is carboxy dextran and another is a modified polymethyl metacrylate (PMMA). The substrates were improved by physical and chemical binding for AFP antibody immobilization. Contact angle and surface Plasmon resonance (SPR) were used to study the characteristic of surfaces. The result was found that the carboxy dextran gave higher detection than PMMA. Moreover, the dextran surface was studied in real serum samples. It was shown the significantly different between positive and negative AFP serum which is preliminary results for testing in more clinical samples further.

Abstract: Peanut protein Ara h2 is one of the serious food allergens contributing to the allergic reaction, causing the common reasons for food-related life threating problems over the world. The objective of this study is to develop single-walled carbon nanotubes (SWCNTs) based biosensor using 1-pyrenibutanoic acid succinimidyl ester (1-PBASE) as a linker for rapid detecting peanut allergen Ara h2 in foods. The detection principal of this biosensor was based upon the binding of Ara h2 to the anti-Ara h2 on the linker-modified SWCNTs connecting gold electrode in biosensor silicon template. The measurements of each step were achieved using linear sweep voltammetry (LSV) with a potentiostat for Ara h2 detection. The application of anti-Ara h2 as pAbs on linker immobilized SWCNTs surface increased the sensor resistance values. The developed biosensor showed significant resistance response with the increase in the concentration of Ara h2 from 0 to 1000 ng/mL. Indirect enzyme-linked immunosorbent assay (ELISA) was successfully applied to confirm the specificity of antibodies using 96-well microplates. Scanning electrone microscopy (SEM) confirmed the microstructure of SWCNTs. Sensor sensitivity and specificity were tested with different peanut allergens and the detection range (1-1000 ng/mL).

Abstract: Improvement of tapered fiber sensor by introducing gold thin layer for facilitating surface plasmon resonance (SPR) generation has been studied. The design of structure has been investigated to generate SPR effectively by a finite element method. The particular interest in this problem is the conditions that determine the formation of evanescent field and the interrogation of the transmission intensity change due to the evanescent field absorption. The fabrication of the tapered fiber was conducted by a technique based on flame brushing. The gold nanolayer was then deposited onto the surface of tapered fiber by sputtering technique. Qualitative agreement between the modeling and experiment results found. The results suggest that a compact sensor based on this structure may be useful for biochemical sensors.

Abstract: Biocompatibility of tin selenide quantum dots was achieved by the incorporation of 3-mercaptopropionic acid (3-MPA) as a capping agent, which also improved the stability and the solubility of the material. The UV-Vis spectrophotometric analysis of the quantum dots revealed a broad absorption band at ~ 330 nm (with a corresponding band gap, E_g, value of 3.75 eV), which is within the range of values expected for quantum dots materials. The 3-mercaptopropionic acid-capped tin selenide (3-MPA-SnSe) quantum dots were used to develop an electrochemical biosensor for indinavir, which is a protease inhibitor antiretroviral (ARV) drug. The biosensor was prepared by the self-assembly of L-cysteine on a gold electrode that was functionalised with 3-MPA-SnSe quantum dots, followed by cross-linking with cytochrome P450-3A4 (CYP3A4) using 1-ethyl-3(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). The electrocatalytic properties of the biosensor included a characteristic cyclic voltammetric reduction peak at-380 mV, which was used to detect the response of the biosensor to indinavir. The sensor performance parameters included response time and limit of detection (LOD) values of 11 s and 3.22 pg/mL, respectively. The test concentration range studied (0.014 – 0.066 ng/mL) gave a linear calibration plot for indinavir, and it was lower than the physiological plasma concentration index (i.e. maximum plasma concentrations, C_max,) of indinavir (5 - 15 ng/mL) normally observed 8 h after intake. This indicates that the biosensor can be very useful in the case of ultra-rapid metabolisers where very low C_max values are expected

Abstract: Biocompatibility of tin selenide quantum dots was achieved by the incorporation of 3-mercaptopropionic acid (3-MPA) as a capping agent, which also improved the stability and the solubility of the material. The UV-Vis spectrophotometric analysis of the quantum dots revealed a broad absorption band at ~ 330 nm (with a corresponding band gap, E_g, value of 3.75 eV), which is within the range of values expected for quantum dots materials. The 3-mercaptopropionic acid-capped tin selenide (3-MPA-SnSe) quantum dots were used to develop an electrochemical biosensor for indinavir, which is a protease inhibitor antiretroviral (ARV) drug. The biosensor was prepared by the self-assembly of L-cysteine on a gold electrode that was functionalised with 3-MPA-SnSe quantum dots, followed by cross-linking with cytochrome P450-3A4 (CYP3A4) using 1-ethyl-3(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). The electrocatalytic properties of the biosensor included a characteristic cyclic voltammetric reduction peak at-380 mV, which was used to detect the response of the biosensor to indinavir. The sensor performance parameters included a response time and sensitivity values of 11 s and 0.221 μA/nM, respectively. The test concentration range studied (0.014 – 0.066 ng/mL) gave a linear calibration plot for indinavir, and it was lower than the physiological plasma concentration index (i.e. maximum plasma concentrations, C_max,) of indinavir (5 - 15 ng/mL) normally observed 8 h after intake. This indicates that the biosensor can be very useful in the case of ultra-rapid metabolisers where very low C_max values are expected

Abstract: Silicon carbide is a well-known wide-band gap semiconductor traditionally used in power electronics and solid-state lighting due to its extremely low intrinsic carrier concentration and high thermal conductivity. What is only recently being discovered is that it possesses excellent compatibility within the biological world. Since publication of the first edition of Silicon Carbide Biotechnology: A Biocompatible Semiconductor for Advanced Biomedical Devices and Applications five years ago [1], significant progress has been made on numerous research and development fronts. In this paper three very promising developments are briefly highlighted – progress towards the realization of a continuous glucose monitoring system, implantable neural interfaces made from free-standing 3C-SiC, and a custom-made low-power ‘wireless capable’ four channel neural recording chip for brain-machine interface applications.

Abstract: Performance of modular surface plasmon resonance (mSPR) sensor based on refractive index is discussed in this paper. The sensor was built in house using a polychromatic light source, polarizer to produce a transverse magnetic wave, high refractive index waveguide, gold-coated disk, single channel cell and spectrometer for data analysis. A knob for adjusting the angle of the incident provides a means for ease of angle variation which simplifies the design of the instrument for portability purposes. In conventional SPR, the light source need to be delocalized for search of the resonance angle, making the instrument bulky in size and had to be laboratory-based. The efficiency of the newly designed SPR biosensor was tested using a various percentages of ethanol in deionized water. Observations on the shifts of the resonance wavelength with ethanol strength revealed that the SPR biosensor has a sensitivity of 64 nm/RIU and a resolution of ~10² RIU.

Abstract: This paper presents the nanofabrication of polymer biosensor structures for biomedical applications. The polymer biosensor structures were achieved using hot embossing technology. The pressure effects on the replication of patterns during the hot embossing of the polymer biosensor structures were investigated. The fabricated polymer biosensor structures with pillar arrays were applied to immunoassay biochips. The pillar shapes of the polymer biosensor structures provided large surface areas and improved the antibody-antigen interaction of the immunoassay biochips.

Abstract: A graphene-based Surface Plasmon Resonance (SPR) biosensor is presented. Graphene layers added to a conventional gold thin film SPR biosensor leads to a drastic increase in sensitivity due to the increased biomolecule adsorption in the graphene layers. In comparison to conventional SPR sensors this produces a large change in the refractive index at the metal-dielectric interface. The reflection of light coupled into a SPR mode propagating along a thin Au-graphene layer surrounded by dielectric is calculated and compared to a conventional SPR sensor.