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Ramasamy, Mohankandhasamy,Yi, Dong Kee,An, Seong Soo A Dove Medical Press 2015 INTERNATIONAL JOURNAL OF NANOMEDICINE Vol.10 No.specal
<P><I>Escherichia coli</I> O157:H7 (O157) is a Gram negative and highly virulent bacteria found in food and water sources, and is a leading cause of chronic diseases worldwide. Diagnosis and prevention from the infection require simple and rapid analysis methods for the detection of pathogens, including O157. Endogenous membrane peroxidase, an enzyme present on the surface of O157, was used for the colorimetric detection of bacteria by catalytic oxidation of the peroxidase substrate. In this study, we have analyzed the impact of the synthesized bare gold nanorods (AuNRs) and silica-coated AuNRs on the growth of <I>E. coli</I> O157. Along with the membrane peroxidase activity of O157, other bacteria strains were analyzed. Different concentrations of nanorods were used to analyze the growth responses, enzymatic changes, and morphological alterations of bacteria by measuring optical density, 3,3′,5,5′-tetramethylbenzidine assay, flow cytometry analysis, and microscopy studies. The results revealed that O157 showed higher and continuous membrane peroxidase activity than other bacteria. Furthermore, O157 treated with bare AuNRs showed a decreased growth rate in comparison with the bacteria with surface modified AuNRs. Interestingly, silica-coated AuNRs favored the growth of bacteria and also increased membrane peroxidase activity. This result can be particularly important for the enzymatic analysis of surface treated AuNRs in various microbiological applicants.</P>
Soluble conducting polymer-functionalized graphene oxide for air-operable actuator fabrication
Ramasamy, M.,Mahapatra, S.,Yoo, H.,Kim, Y.,Cho, J. Royal Society of Chemistry 2014 Journal of Materials Chemistry A Vol.2 No.13
An effective route for the preparation of a processable, conducting polymer-functionalized graphene oxide for actuator applications is investigated. First, graphene oxide (GO) is covalently functionalized with a 3-thiophene acetic acid (TAA) monomer by an esterification reaction. Then, the TAA-functionalized GO is self-polymerized by chemical oxidative polymerization to yield poly(3-thiophene acetic acid)functionalized GO (GO-f-PTAA). Further, the GO-f-TAA is also copolymerized with thiophene (Th) to yield GO-f-PTAA-co-PTh. The synthesis of GO-f-PTAA and GO-f-PTAA-co-PTh composites is confirmed by Fourier transform infrared, H-1-nuclear magnetic resonance, and X-ray photoelectron spectroscopies. The composites show better electrochemical properties than pure PTAA and superior solubility in organic solvents compared to pure GO. Using the soluble GO-f-PTAA and GO-f-PTAA-co-PTh composites, air-operable actuators are fabricated and their actuation performance is investigated. The copolymer-functionalized GO actuator exhibits good electroactive actuation behavior between 2 and 4 V, mainly because of the enhanced electrochemical performance of the composites, whereas the pure PTAA and GO-f-PTAA actuators do not show actuation under the applied voltage. The soluble conducting polymer-functionalized graphene composites developed in this study have potential applications in the fabrication of actuators that can be operated in air.
Drug and bioactive molecule screening based on a bioelectrical impedance cell culture platform
Ramasamy, Sakthivel,Bennet, Devasier,Kim, Sanghyo Dove Medical Press 2014 INTERNATIONAL JOURNAL OF NANOMEDICINE Vol.9 No.-
<P>This review will present a brief discussion on the recent advancements of bioelectrical impedance cell-based biosensors, especially the electric cell-substrate impedance sensing (ECIS) system for screening of various bioactive molecules. The different technical integrations of various chip types, working principles, measurement systems, and applications for drug targeting of molecules in cells are highlighted in this paper. Screening of bioactive molecules based on electric cell-substrate impedance sensing is a trial-and-error process toward the development of therapeutically active agents for drug discovery and therapeutics. In general, bioactive molecule screening can be used to identify active molecular targets for various diseases and toxicity at the cellular level with nanoscale resolution. In the innovation and screening of new drugs or bioactive molecules, the activeness, the efficacy of the compound, and safety in biological systems are the main concerns on which determination of drug candidates is based. Further, drug discovery and screening of compounds are often performed in cell-based test systems in order to reduce costs and save time. Moreover, this system can provide more relevant results in in vivo studies, as well as high-throughput drug screening for various diseases during the early stages of drug discovery. Recently, MEMS technologies and integration with image detection techniques have been employed successfully. These new technologies and their possible ongoing transformations are addressed. Select reports are outlined, and not all the work that has been performed in the field of drug screening and development is covered.</P>
Wurtzite Cu???GeS??? Nanocrystals: Phase- and Shape-Controlled Colloidal Synthesis.
Ramasamy, Parthiban,Kim, Jinkwon Wiley-VCH 2015 Chemistry - An Asian Journal Vol.10 No.7
<P>The first colloidal synthesis of Cu2GeS3 (CGS) nanocrystals with a thermodynamically metastable wurtzite crystal phase is reported. As a benefit of the sulfur precursors used in the synthesis, the shape of the as-synthesized wurtzite CGS nanocrystals can be controlled in the form of spherical nanoparticles, nanorectangles, and hollow nanorectangles. A detailed investigation into the effects of reaction conditions necessary to obtain phase-pure wurtzite CGS nanocrystals is presented. The choice of sulfur precursor and precursor injection temperature play a significant role in determining the crystal phase of the CGS nanocrystals. The band gap of the new wurtzite phase CGS was measured to be 1.76eV and the CGS nanocrystals exhibited a good electrochemical photoresponse, which was indicative of their potential application as an active layer in the field of solar cells.</P>
Ramasamy, T.,Ruttala, H. B.,Choi, J. Y.,Tran, T. H.,Kim, J. H.,Ku, S. K.,Choi, H. G.,Yong, C. S.,Kim, J. O. The Royal Society of Chemistry 2015 Chemical communications Vol.51 No.26
<P>We developed a highly stable lipid-polymer nanoarchitectural platform for effective combination therapy of doxorubicin and irinotecan in the polyelectrolyte complex nanoparticle core, followed by incorporation of the whole assembly into a lecithin bilayer. It shows great potential for the treatment of a broad range of cancers.</P> <P>Graphic Abstract</P><P>We developed a highly stable lipid-polymer nanoarchitectural platform for effective combination therapy of doxorubicin and irinotecan in the polyelectrolyte complex nanoparticle core, followed by incorporation of the whole assembly into a lecithin bilayer. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c5cc00482a'> </P>
Ramasamy, Easwaramoorthi,Jo, Changshin,Anthonysamy, Arockiam,Jeong, Inyoung,Kim, Jin Kon,Lee, Jinwoo American Chemical Society 2012 Chemistry of materials Vol.24 No.9
<P>Ordered mesoporous titanium nitride-carbon (denoted as OM TiN-C) nanocomposite with high surface area (389 m<SUP>2</SUP> g<SUP>–1</SUP>) and uniform hexagonal mesopores (ca. 5.5 nm) was facilely synthesized via the soft-template method. As a structure-directing agent, Pluronic F127 triblock copolymer formed an ordered structure with inorganic precursors, resol polymer, and prehydrolyzed TiCl<SUB>4</SUB>, followed by a successive heating at 700 °C under nitrogen and ammonia flow. In this study, the amorphous carbon within the parent OM TiO<SUB>2</SUB>-C acted as a rigid support, preventing structural collapse during the conversion process of TiO<SUB>2</SUB> nanocrystals to TiN nanocrystals. The OM TiN-C was then successfully applied as counter electrode material in dye-sensitized solar cells (DSCs). The organic electrolyte disulfide/thiolate (T<SUB>2</SUB>/T<SUP>–</SUP>) was introduced to study the electrocatalytic property of the OM TiN-C nanocomposite. Because of the existence of TiN nanocrystals and the defect sites of the amorphous carbon, the DSCs using OM TiN-C as a counter electrode showed 6.71% energy conversion efficiency (platinum counter electrode DSCs: 3.32%) in the organic electrolyte system (T<SUB>2</SUB>/T<SUP>–</SUP>). Furthermore, the OM TiN-C counter electrode based DSCs showed an energy conversion efficiency of 8.41%, whereas the DSCs using platinum as a counter electrode showed a conversion efficiency of only 8.0% in an iodide electrolyte system. The superior performance of OM TiN-C counter electrode resulted from the low charge transfer resistance, enhanced electrical conductivity, and abundance of active sites of the OM TiN-C nanocomposite. Moreover, OM TiN-C counter electrode showed better chemical stability in organic electrolyte compared with the platinum counter electrode.</P><P>Ordered mesoporous titanium nitride-carbon (OM TiN-C) nanocomposites were synthesized, for the first time, using a simple soft-template method. The iodine-free organic electrolyte dye-sensitized solar cells using OM TiN-C nanocomposite counter electrodes exhibited high efficiency (6.71%), that is, a performance 2-fold greater than that of conventional Pt counter electrode DSCs (fill factor: 0.33, efficiency: 3.32%).</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2012/cmatex.2012.24.issue-9/cm203672g/production/images/medium/cm-2011-03672g_0012.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm203672g'>ACS Electronic Supporting Info</A></P>