Publications Archives – Page 3 of 11 – Institute of Nano Electronic Engineering

Eco-friendly synthesis of Solanum trilobatum extract-capped silver nanoparticles is compatible with good antimicrobial activities

March 19, 2018 By Editor

Abstract – This study focused on the evaluation of antimicrobial activity of silver nanoparticles (AgNPs) after their green synthesis by means of a Solanum trilobatum bark extract. The obtained product with an intense surface plasmon resonance band at ∼442 nm with UV–visible spectroscopic analysis indicated the formation of AgNPs. The morphology of AgNPs was observed under transmission electron microscopy and field emission scanning electron microscopy, displayed that the eco-friendly synthesized AgNPs have a spherical shape with an average size of ∼25 nm in diameter. X-ray powder diffraction and selected area electron diffraction analyses confirmed that the AgNPs are crystalline in nature. Fourier transform infrared spectroscopy indicated that the AgNPs capped with active ingredients of the bark extract. X-ray photoelectron spectroscopy revealed elemental composition of the AgNPs. The performance of S. trilobatum bark extract-capped AgNPs in terms of inhibition of microbial growth was studied by disc diffusion and well diffusion assays. Eco-friendly synthesized S. trilobatum extract-capped AgNPs were found to possess enhanced antimicrobial properties: growth inhibition of gram-negative and gram-positive bacteria and of fungal species. These results demonstrated the potential applications of the indigenous medicinal plants to the field of nanotechnology.

Corresponding Author: Subash C B Gopinath
Corresponding Author’s Email: subash@unimap.edu.my

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Reduced graphene oxide–multiwalled carbon nanotubes composites as sensing membrane electrodes for DNA detection

December 12, 2017 By Editor

Abstract – Thin films of reduced graphene oxide–multiwalled carbon nanotube (rGO–MWCNT) composites were demonstrated as sensing membrane electrodes for single-stranded DNA (ssDNA) detection. The morphology of the rGO–MWCNT composite thin films was observed via field emission scanning electron microscopy. The GO sheet and MWCNTs were clearly obtained, and the MWCNTs were uniformly distributed on the surface of the GO. The chemical bonding of the rGO–MWCNTs was examined using Fourier transform infrared spectroscopy. The element compositions of carbon, silicon, and oxygen were confirmed via energy-dispersive X-ray spectroscopy and X-ray powder diffraction analysis. The biosensor demonstrated high sensitivity to the ssDNA target with a linear range from 500 to 100 pM. Furthermore, the biosensor demonstrated good selectivity, reproducibility, and long-term stability for DNA detection. Since, the biosensor responded very-well and demonstrated excellent detection capabilities, it is highly recommended to be used in detecting specific biomarkers and other targeted proteins.

Corresponding Author: Ruslinda A. Rahim
Corresponding Author’s Email: ruslinda@unimap.edu.my

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Selectivity verification of cardiac troponin monoclonal antibodies for cardiac troponin detection by using conventional ELISA

July 16, 2017 By Editor

Abstract – This paper presents preparation and characterization of conventional enzyme-linked immunosorbent assay (ELISA) for cardiac troponin detection to determine the selectivity of the cardiac troponin monoclonal antibodies. Monoclonal antibodies, used to capture and bind the targets in this experiment, are cTnI monoclonal antibody (MAb-cTnI) and cTnT monoclonal antibody (MAb-cTnT), while both cardiac troponin I (cTnI) and T (cTnT) are used as targets. ELISA is performed inside two microtiter plates for MAb-cTnI and MAb-cTnT. For each plate, monoclonal antibodies are tested by various concentrations of cTnI and cTnT ranging from 0-6400 μg/l. The binding selectivity and level of detection between monoclonal antibodies and antigen are determined through visual observation based on the color change inside each well on the plate. ELISA reader is further used to quantitatively measured the optical density of the color changes, thus produced more accurate reading. The results from this experiment are utilized to justify the use of these monoclonal antibodies as bio-receptors for cardiac troponin detection by using field-effect transistor (FET)-based biosensors coupled with substrate-gate in the future.

Corresponding Author: Ruslinda A. Rahim
Corresponding Author’s Email: ruslinda@unimap.edu.my

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Current and Potential Developments of Cortisol Aptasensing towards Point-of-Care Diagnostics (POTC)

May 27, 2017 By Editor

Abstract – Anxiety is a psychological problem that often emerges during the normal course of human life. The detection of anxiety often involves a physical exam and a self-reporting questionnaire. However, these approaches have limitations, as the data might lack reliability and consistency upon application to the same population over time. Furthermore, there might be varying understanding and interpretations of the particular question by the participant, which necessitating the approach of using biomarker-based measurement for stress diagnosis. The most prominent biomarker related to stress, hormone cortisol, plays a key role in the fight-or-flight situation, alters the immune response, and suppresses the digestive and the reproductive systems. We have taken the endeavour to review the available aptamer-based biosensor (aptasensor) for cortisol detection. The potential point-of-care diagnostic strategies that could be harnessed for the aptasensing of cortisol were also envisaged.

Keywords – anxiety, cortisol, aptasensor, aptamer

Corresponding Author: Ruslinda A. Rahim
Corresponding Author’s Email: ruslinda@unimap.edu.my

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Substrate-gate coupling in ZnO-FET biosensor for cardiac troponin I detection

March 17, 2017 By Editor

Abstract – Currently, field-effect transistor (FET)-based biosensors have been implemented in several portable sensors with the ultimate application in point-of-care testing (POCT). In this paper, we have designed substrate-gate coupling in FET-based biosensor for the detection of cardiac troponin I (cTnI) biomarker. In the device structure, zinc oxide nanoparticles (ZnO-NPs) thin film were deposited through sol-gel and spin coating techniques on the channel. The p-type silicon was used as a substrate, while ZnO is an n-type nanomaterial, thus creates p-n-p junction between source, channel, and drain. The deposited thin films exhibited hexagonal wurtzite phase of ZnO, suitable for biomolecular interaction as revealed in X-ray diffraction (XRD) analysis. The surface of the thin film was then functionalized with 3-aminopropyltriethoxysilane (APTES), followed by glutaraldehyde (GA) as a bi-functional linker to immobilize the cTnI monoclonal antibody (MAb-cTnI) as bio-receptor for capturing cTnI biomarker and proven by the Fourier transform-infrared (FT-IR) spectra. Lastly, we demonstrated a new strategy, the integration of FET-based biosensors with substrate-gate showed differences between before (immobilization) and after cTnI target biomarker interaction by significant changes in drain current (ID) and change of threshold voltage (VT), which improved the sensitive detection, with the limit of detection down to 3.24 pg/ml.

Keywords – Biosensor, Cardiac troponin I, Electrical-based, Field-effect transistor, Substrate-gate coupling, Zinc oxide nanoparticles

Corresponding Author: Uda Hashim
Corresponding Author’s Email: uda@unimap.edu.my

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