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RISS 인기검색어
- 검색키워드
- 저자 : Waleed Ahmed El-Said (검색결과 23 건)
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Waleed Ahmed El-Said,최정우 한국생물공학회 2014 Biotechnology and Bioprocess Engineering Vol.19 No.6
Rat pheochromocytoma PC12 cells havefrequently been used as a dopaminergic neuron model dueto their various functions, including the synthesis, storage,and secretion of catecholamines. Furthermore, PC12 cellsrelease a measurable amount of dopamine (DA) in responseto some chemicals. PC12 cells are thus considered to beone of the most common invitro models for studyingneurotransmitter release. Here, we applied Surface-enhancedRaman Spectroscopy (SERS) to determine with highsensitivity the in-situ short-time effects of cisplatin (cisdiamine-dichloroplatinum), bisphenol-A, and cyclophosphamideon the extracellular DA level released from PC12cells. In addition, using the SERS technique, changes in thebiochemical composition of the PC12 cell lysates wereinvestigated to determine the intracellular DA level. Goldnano-patterned substrates were fabricated based on electrochemicaldeposition of Au nanorods onto ITO substrates;these substrates were then used as SERS-active surfaces. The Raman spectroscopy results demonstrated that thechanges in the Raman spectra depending on the treatmentagent were in agreement with the HPLC results on theextracellular DA level. Therefore, the SERS technique canovercome the limitations of other detection techniques, andcan be used with cellular nanoarrays to study the effect ofa wide range of chemicals.
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El-Said, Waleed Ahmed,Kim, Tae-Hyung,Yea, Cheol-Heon,Kim, Hyuncheol,Choi, Jeong-Woo American Scientific Publishers 2011 Journal of nanoscience and nanotechnology Vol.11 No.1
<P>Alzheimer's disease is a progressive neurodegenerative disorder that is characterized by the deposition of beta-amyloid (Abeta) peptide and the formation of neurofibrillary tangles in neurons. The Abeta peptide is a key molecule in the pathogenesis of Alzheimer's disease and an important marker for early diagnosis. Surface-enhanced Raman scattering (SERS) has recently been attracting keen interest in various fields such as for biosensors or immunoassays. In this study, gold nanoparticles (Au NPs) were electrochemically deposited on an indium tin oxide (ITO) substrate at different heights. Abeta antibodies were immobilized on the Au-NP-coated ITO substrate, after which the interactions between the antigen and the antibody were determined via SERS spectroscopy. The SERS responses were strongest at the Au NP array height of 91 nm, with a good linear relationship that corresponded to the change in the concentration of the antigen. This Au-NP-array-mediated SERS can be applied with a highly sensitive immunodetection biosensor.</P>
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Three-dimensional mesoporous gold film to enhance the sensitivity of electrochemical detection
El-Said, Waleed Ahmed,Kim, Tae-Hyung,Kim, Hyuncheol,Choi, Jeong-Woo IOP Pub 2010 Nanotechnology Vol.21 No.45
<P>Cell–cell and cell–extracellular matrix (ECM) adhesion are fundamental and important in the development of a cell-based chip. In this study, a novel, simple, rapid, and one-step technique was developed for the fabrication of a uniform three-dimensional mesoporous gold thin film (MPGF) onto a gold (Au) coated glass plate based on an electrochemical deposition method. Scanning electron microscopy images demonstrated that the resulting MPGF electrode had uniformly distributed pores with diameters of about 20 nm. The cyclic voltammetric behavior of [Fe(CN)<SUB>6</SUB>]<SUP>4 − /3 − </SUP> coupled onto MPGF and Au electrodes demonstrated that the MPGF electrode had a higher electrocatalytic sensitivity and reversibility than the bare Au electrode. The Arg–Gly–Asp (RGD) sequence containing the peptide was immobilized on the MPGF and bare Au substrates. HeLa cancer cells were then cultured on the RGD peptide layer. The successful immobilization of the peptide and cells was confirmed by atomic force microscopy. The cell proliferation and viability were evaluated by cyclic voltammetry and Trypan blue dyeing assay. These results indicated that the RGD/MPGF modified electrodes showed an electrochemical sensitivity in the detection of cancer cells which is approximately three times higher, especially at low cell density, than RGD/Au electrodes. This much improved sensitivity of the MPGF modified electrode demonstrates the potential for the fabrication of a highly sensitive and low-cost cell-based chip for rapid cancer detection. </P>
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Waleed Ahmed El-Said,Cheol-Heon Yea,Hyunhee Kim,최정우 한국물리학회 2009 Current Applied Physics Vol.9 No.2
HepG2 cells have been immobilized on nanoscale self-assembled synthetic oligopeptide modified chip surface and subsequently used for anticancer drug screening. Nanoscale controlled self-assembled peptide layer was investigated by AFM (Atomic Force Microscopy). The immobilization of HepG2 cells on nanoscale controlled surface was investigated by using Raman spectroscopy. HepG2 cells were grown on peptide modified gold surface acting as working electrode. The AFM investigation of the oligopeptide modified surface showed excellent agreement with the nanoscale nature of the peptide modification, and the voltammetric response of HepG2 cells on this surface towards an anticancer drug showed a linear relationship with the cell number. As an application, electrochemical detection of anticancer drug effect of HepG2 cells was shown. These results indicate that RGD (Arg-Gly-Asp) peptide self-assembled layer mediated the cell immobilization technique and the voltammetric signal analysis system can be applied to construct a cell chip for diagnosis, drug detection, and on-site monitoring. HepG2 cells have been immobilized on nanoscale self-assembled synthetic oligopeptide modified chip surface and subsequently used for anticancer drug screening. Nanoscale controlled self-assembled peptide layer was investigated by AFM (Atomic Force Microscopy). The immobilization of HepG2 cells on nanoscale controlled surface was investigated by using Raman spectroscopy. HepG2 cells were grown on peptide modified gold surface acting as working electrode. The AFM investigation of the oligopeptide modified surface showed excellent agreement with the nanoscale nature of the peptide modification, and the voltammetric response of HepG2 cells on this surface towards an anticancer drug showed a linear relationship with the cell number. As an application, electrochemical detection of anticancer drug effect of HepG2 cells was shown. These results indicate that RGD (Arg-Gly-Asp) peptide self-assembled layer mediated the cell immobilization technique and the voltammetric signal analysis system can be applied to construct a cell chip for diagnosis, drug detection, and on-site monitoring.
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Waleed Ahmed El-Said,예철헌,권일근,최정우 한국바이오칩학회 2009 BioChip Journal Vol.3 No.2
The effect of anticancer drugs and toxins on the viabiity of HepG2 cells were examined by the cyclic voltammetry (CV) and the potentiometric stripping analysis (PSA) methods. The cells were immobilized on gold patterned silicon substrate. The voltammetric behaviors of HepG2 cells showed a quasi-reversible process and the peak current showed a linear relationship with cell number. The attached living cells were treated with different concentrations of anticancer drugs and toxin. As the exposed concentrations of anticancer drugs and toxins were increased, we observed that the peak current in CV assay and the area under the peak in PSA assay were decreased. Trypan blue dyeing experiment was performed to confirm the results of the effects of anticancer drugs on the cell viability which were obtained from CV assay and PSA assay. These results indicate that the proposed direct cell immobilization method technique can be applied to construct the cell chip for the diagnosis, drug detection, and on-site monitoring depended on the voltammetric and PSA methods.
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Electrochemical sensor to detect neurotransmitter using gold nano-island coated ITO electrode.
El-Said, Waleed Ahmed,Lee, Jin-Ho,Oh, Byung-Keun,Choi, Jeong-Woo American Scientific Publishers 2011 Journal of Nanoscience and Nanotechnology Vol.11 No.7
<P>Parkinson disease is a chronic neurodegenerative disorder characterized by the loss of dopamine, which is a neurotransmitter in the substantia nigra. In this study, a simple, rapid and inexpensive method to fabricate gold nano-island film (GNIF) coated ITO electrode has been developed based on electrochemical deposition of Au onto ITO substrate. The nanostructured film surface was characterized by scanning electron microscopy (SEM). Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to evaluate the electrochemical behavior of induvidul dopamine and uric acid solution were studied. Moreover, GNIF/ITO electrode was applied to detecte DA in the presence of Bovine Serum Albumin (50 microM) as an interference. These results demonstrate that, interfering component has no effect on the determination of DA at GNIF electrode, hence this GNIF electrode is suitable for the determination of DA with high sensitivity and selectivity. Then, GNIF coated ITO electrode was applied to monitor the electrochemical simultaneous detection of dopamine and uric acid mixtures based on CV and DPV with high sensitivity. GNIF-modified ITO electrode showed a linear range for the determination of dopamine concentration from 0.1 microM to 40 microM in the presence of 50 microM of uric acid. Based on these results, the proposed technique can be a promising method to construct a highly sensitive biosensor as well as highly efficient protein chip.</P>
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Jung, Mi,El-Said, Waleed Ahmed,Choi, Jeong-Woo IOP Pub 2011 Nanotechnology Vol.22 No.23
<P>Two-dimensional gold (Au) nanodot arrays on a transparent substrate were fabricated for imaging of living cells. A nanoporous alumina mask with large-area coverage capability was prepared by a two-step chemical wet etching process after a second anodization. Highly ordered Au nanodot arrays were formed on indium–tin-oxide (ITO) glass using very thin nanoporous alumina of approximately 200 nm thickness as an evaporation mask. The large-area Au nanodot arrays on ITO glass were modified with RGD peptide (arginine; glycine; aspartic acid) containing a cysteine (Cys) residue and then used to immobilize human cancer HeLa cells, the morphology of which was observed by confocal microscopy. The confocal micrographs of living HeLa cells on Au nanodot arrays revealed enhanced contrast and resolution, which enabled discernment of cytoplasmic organelles more clearly. These results suggest that two-dimensional Au nanodot arrays modified with RGD peptide on ITO glass have potential as a biocompatible nanobioplatform for the label-free visualization and adhesion of living cells.</P>
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