Electrodeposition of Pt-Pb nanoparticles (PtPbNPs) to multi-walled carbon nanotubes (MWCNTs) resu... more Electrodeposition of Pt-Pb nanoparticles (PtPbNPs) to multi-walled carbon nanotubes (MWCNTs) resulted in a stable PtPbNP/MWCNT nanocomposite with high electrocatalytic activity to glucose oxidation in either neutral or alkaline medium. More importantly, the nanocomposite electrode with a slight modification exhibited high sensitivity, high selectivity, and low detection limit in amperometric glucose sensing at physiological neutral pH (poised at a negative potential). At +0.30 V in neutral solution, the nanocomposite electrode exhibited linearity up to 11 mM of glucose with a sensitivity of 17.8 microA cm(-2) mM(-1) and a detection limit of 1.8 microM (S/N=3). Electroactive ascorbic acid (0.1 mM), uric acid (0.1 mM) and fructose (0.3 mM) invoked only 23%, 14% and 9%, respectively, of the current response obtained for 3 mM glucose. At -0.15 V in neutral solution, the electrode responded linearly to glucose up to 5 mM with a detection limit of 0.16 mM (S/N=3) and detection sensitivity of approximately 18 microA cm(-2) mM(-1). At this negative potential, ascorbic acid, uric acid, and fructose were not electroactive, therefore, not interfering with glucose sensing. Modification of the nanocomposite electrode with Nafion coating followed by electrodeposition of a second layer of PtPbNPs on the Nafion coated PtPbNP/MWCNT nanocomposite produced a glucose sensor (poised at -0.15 V) with a lower detection limit (7.0 microM at S/N=3) and comparable sensitivity, selectivity and linearity compared to the PtPbNP/MWCNT nanocomposite. The Nafion coating lowered the detection limit by reducing the background noise, while the second layer of PtPbNPs restored the sensitivity to the level before Nafion coating.
ABSTRACT We report the design and fabrication of a novel single cell electroporation biochip feat... more ABSTRACT We report the design and fabrication of a novel single cell electroporation biochip featuring high aspect ratio nickel micro-electrodes with smooth side walls between which individual cells are attached. The biochip is fabricated using Proton Beam Writing (PBW), a new direct write lithographic technique capable of fabricating high quality high-aspect-ratio nano and microstructures. By applying electrical impulses across the biochip electrodes, SYTOX® Green nucleic acid stain is incorporated into mouse neuroblastoma (N2a) cells and observed via green fluorescence when the stain binds with DNA inside the cell nucleus. Three parameters; electric field strength, pulse duration, and numbers of pulses have been investigated for the single cell electroporation process. The results indicate high transfection rates as well as cell viability of 82.1 and 86.7% respectively. This single cell electroporation system may represent a promising method for the introduction of a wide variety of fluorophores, nanoparticles, quantum dots, DNAs and proteins into cells.
Publisher Summary This chapter describes the procedure for the preparation of protein kinase C is... more Publisher Summary This chapter describes the procedure for the preparation of protein kinase C isozymes and substrates from rat brain. The potential importance of protein kinase C (PKC) in the regulation of nervous functions has been well recognized. Both the short-term responses associated with neurotransmitter release, modulation of ion channels, regulation of receptor functions, and cellular metabolism as well as long-term responses that are involved in the enhancement of synaptic plasticity and control of growth and differentiation have been linked to the action of PKC. PKC α, β, γ, and ɛ are copurified from the rat brain extract during the early stage of purification, and the resolution of each isozyme is achieved at the final step by hydroxylapatite column chromatography. Fractions containing the major PKC α, β, and γ and those also containing PKC ɛ are concentrated separately in Amicon cells and exchanged with buffer B by repetitive dilution and concentration. The cofactor requirements of the PKC-catalyzed reaction depend on the substrates used in the assay. With histone H1 as a substrate, PKC α, β, and γ are stimulated by Ca2+, PS, and DAG or phorbol ester, PKC δ and ɛ are stimulated by PS and DAG, and PKC ζ is stimulated by PS alone. Significant variations in the cofactor requirement are related to the interactions among the various components in the assay. Identification of these PKC substrates during purification is based on the apparent Mr on SDS-PAGE, immunoreactivities toward specific antibodies, and elution profiles on the C4 reversed-phase column. It should be noted that these proteins are frequently eluted from the C4 column as cluster of peaks of the same Mr. Calmodulin, which binds neuromodulin, neurogranin, and MARCKS at a domain adjacent to the PKC phosphorylation site(s), exerts its inhibitory effect by hindering the access of the kinase to the substrates.
Journal of Pharmacology and Experimental Therapeutics, Jun 30, 2006
Dose-limiting diarrhea and myelosuppression compromise the success of irinotecan (7-ethyl-10-[4-[... more Dose-limiting diarrhea and myelosuppression compromise the success of irinotecan (7-ethyl-10-[4-[1-piperidino]-1-piperidino]carbonyloxycamptothecin) (CPT-11)-based chemotherapy. A recent pilot study indicates that thalidomide attenuates the toxicity of CPT-11 in cancer patients. This study aimed to investigate whether coadministered thalidomide modulated the toxicities of CPT-11 and the underlying mechanisms using several in vivo and in vitro models. Diarrhea, intestinal lesions, cytokine expression, and intestinal epithelial apoptosis were monitored. Coadministered thalidomide (100 mg/kg i.p. for 8 days) significantly attenuated body weight loss, myelosuppression, diarrhea, and intestinal histological lesions caused by CPT-11 (60 mg/kg i.v. for 4 days). This was accompanied by inhibition of tumor necrosis factor-alpha, interleukins 1 and 6 and interferon-gamma, and intestinal epithelial apoptosis. Coadministered thalidomide also significantly increased the systemic exposure of CPT-11 but decreased that of SN-38 (7-ethyl-10-hydroxycampothecin). It significantly reduced the biliary excretion and cecal exposure of CPT-11, SN-38, and SN-38 glucuronide. Thalidomide hydrolytic products inhibited hydrolysis of CPT-11 in rat liver microsomes but not in primary rat hepatocytes. In addition, thalidomide and its major hydrolytic products, such as phthaloyl glutamic acid (PGA), increased the intracellular accumulation of CPT-11 and SN-38 in primary rat hepatocytes. They also significantly decreased the transport of CPT-11 and SN-38 in Caco-2 and parental MDCKII cells. Thalidomide and PGA also significantly inhibited P-glycoprotein (PgP/MDR1), multidrug resistance-associated protein (MRP1)- and MRP2-mediated CPT-11 and SN-38 transport in MDCKII cells. These results provide insights into the pharmacodynamic and pharmacokinetic mechanisms for the protective effects of thalidomide against CPT-11-induced intestinal toxicity.
... LI Zheng-qiang 1* * , LI Xiao-yuan1 , SHEU Fwu-shan2, CHEN Dong-ming 1 and YU Nai-teng 1 ( 1 ... more ... LI Zheng-qiang 1* * , LI Xiao-yuan1 , SHEU Fwu-shan2, CHEN Dong-ming 1 and YU Nai-teng 1 ( 1 Department of Chemistry, 2 Department of Biochemistry, H ong K ong University of Science & T echnology, H ong K ong ) (Received April 4, 1997) ...
Microchim Acta (2008) 162: 235243 DOI 10.1007/s00604-007-0882-0 Printed in The Netherlands ... E... more Microchim Acta (2008) 162: 235243 DOI 10.1007/s00604-007-0882-0 Printed in The Netherlands ... Electrocatalytic oxidation of methanol on a platinum modified carbon nanotube electrode ... Ying Wen1,2, Jian-Shan Ye3,4, Wei-De Zhang3, Fwu-Shan Sheu4, Guo Qin Xu2
Previous correlative and interventive work from this laboratory has suggested that activation of ... more Previous correlative and interventive work from this laboratory has suggested that activation of protein kinase C (PKC) is important for the maintenance of the hippocampal long-term potentiation (LTP) response. One such study demonstrated that application of the cis- unsaturated fatty acid, oleate, a newly discovered PKC activator, could prolong the time course of LTP. The present study explored the mechanism of cis-unsaturated fatty acid action on LTP produced by perforant path stimulation. First, neither oleate application nor high- frequency stimulation alone produced a persistent change in synaptic transmission, while the 2 in conjunction did so. This suggests that oleate acts synergistically with the consequences of this stimulation to produce an enhancement of the LTP response. Second, oleate enhancement of LTP was more potent when applied in the perforant path synaptic terminal zone than in the dentate hilus, implying that the site of oleate action is at the synapse (where PK...
Platinum nanoparticles were electrochemically deposited onto highly oriented pyrolitic graphite (... more Platinum nanoparticles were electrochemically deposited onto highly oriented pyrolitic graphite (HOPG) from H2PtCl6 solutions and observed by tapping mode atomic force microscopy. Spontaneous Pt deposition, which resulted in a wide particle size distribution, would occur on HOPG at open-circuit potential but could be suppressed by using anodic bias of the substrate before and after deposition. Nanoparticles with a narrow size distribution could be obtained when spontaneous reduction was avoided. Pt nucleated both at step edges and on terraces, with a preference for the former. The density of Pt nanoparticles on HOPG was 109–1010cm−2. Increasing the deposition overpotential or adding HCl as supporting electrolyte resulted in more uniform particles and less aggregation. These findings confirm previous results obtained by our group using only electrochemical methods [G. Lu, G. Zangari, J. Phys. Chem. B 109 (2005) 7998].
Electrodeposition of Pt-Pb nanoparticles (PtPbNPs) to multi-walled carbon nanotubes (MWCNTs) resu... more Electrodeposition of Pt-Pb nanoparticles (PtPbNPs) to multi-walled carbon nanotubes (MWCNTs) resulted in a stable PtPbNP/MWCNT nanocomposite with high electrocatalytic activity to glucose oxidation in either neutral or alkaline medium. More importantly, the nanocomposite electrode with a slight modification exhibited high sensitivity, high selectivity, and low detection limit in amperometric glucose sensing at physiological neutral pH (poised at a negative potential). At +0.30 V in neutral solution, the nanocomposite electrode exhibited linearity up to 11 mM of glucose with a sensitivity of 17.8 microA cm(-2) mM(-1) and a detection limit of 1.8 microM (S/N=3). Electroactive ascorbic acid (0.1 mM), uric acid (0.1 mM) and fructose (0.3 mM) invoked only 23%, 14% and 9%, respectively, of the current response obtained for 3 mM glucose. At -0.15 V in neutral solution, the electrode responded linearly to glucose up to 5 mM with a detection limit of 0.16 mM (S/N=3) and detection sensitivity of approximately 18 microA cm(-2) mM(-1). At this negative potential, ascorbic acid, uric acid, and fructose were not electroactive, therefore, not interfering with glucose sensing. Modification of the nanocomposite electrode with Nafion coating followed by electrodeposition of a second layer of PtPbNPs on the Nafion coated PtPbNP/MWCNT nanocomposite produced a glucose sensor (poised at -0.15 V) with a lower detection limit (7.0 microM at S/N=3) and comparable sensitivity, selectivity and linearity compared to the PtPbNP/MWCNT nanocomposite. The Nafion coating lowered the detection limit by reducing the background noise, while the second layer of PtPbNPs restored the sensitivity to the level before Nafion coating.
ABSTRACT We report the design and fabrication of a novel single cell electroporation biochip feat... more ABSTRACT We report the design and fabrication of a novel single cell electroporation biochip featuring high aspect ratio nickel micro-electrodes with smooth side walls between which individual cells are attached. The biochip is fabricated using Proton Beam Writing (PBW), a new direct write lithographic technique capable of fabricating high quality high-aspect-ratio nano and microstructures. By applying electrical impulses across the biochip electrodes, SYTOX® Green nucleic acid stain is incorporated into mouse neuroblastoma (N2a) cells and observed via green fluorescence when the stain binds with DNA inside the cell nucleus. Three parameters; electric field strength, pulse duration, and numbers of pulses have been investigated for the single cell electroporation process. The results indicate high transfection rates as well as cell viability of 82.1 and 86.7% respectively. This single cell electroporation system may represent a promising method for the introduction of a wide variety of fluorophores, nanoparticles, quantum dots, DNAs and proteins into cells.
Publisher Summary This chapter describes the procedure for the preparation of protein kinase C is... more Publisher Summary This chapter describes the procedure for the preparation of protein kinase C isozymes and substrates from rat brain. The potential importance of protein kinase C (PKC) in the regulation of nervous functions has been well recognized. Both the short-term responses associated with neurotransmitter release, modulation of ion channels, regulation of receptor functions, and cellular metabolism as well as long-term responses that are involved in the enhancement of synaptic plasticity and control of growth and differentiation have been linked to the action of PKC. PKC α, β, γ, and ɛ are copurified from the rat brain extract during the early stage of purification, and the resolution of each isozyme is achieved at the final step by hydroxylapatite column chromatography. Fractions containing the major PKC α, β, and γ and those also containing PKC ɛ are concentrated separately in Amicon cells and exchanged with buffer B by repetitive dilution and concentration. The cofactor requirements of the PKC-catalyzed reaction depend on the substrates used in the assay. With histone H1 as a substrate, PKC α, β, and γ are stimulated by Ca2+, PS, and DAG or phorbol ester, PKC δ and ɛ are stimulated by PS and DAG, and PKC ζ is stimulated by PS alone. Significant variations in the cofactor requirement are related to the interactions among the various components in the assay. Identification of these PKC substrates during purification is based on the apparent Mr on SDS-PAGE, immunoreactivities toward specific antibodies, and elution profiles on the C4 reversed-phase column. It should be noted that these proteins are frequently eluted from the C4 column as cluster of peaks of the same Mr. Calmodulin, which binds neuromodulin, neurogranin, and MARCKS at a domain adjacent to the PKC phosphorylation site(s), exerts its inhibitory effect by hindering the access of the kinase to the substrates.
Journal of Pharmacology and Experimental Therapeutics, Jun 30, 2006
Dose-limiting diarrhea and myelosuppression compromise the success of irinotecan (7-ethyl-10-[4-[... more Dose-limiting diarrhea and myelosuppression compromise the success of irinotecan (7-ethyl-10-[4-[1-piperidino]-1-piperidino]carbonyloxycamptothecin) (CPT-11)-based chemotherapy. A recent pilot study indicates that thalidomide attenuates the toxicity of CPT-11 in cancer patients. This study aimed to investigate whether coadministered thalidomide modulated the toxicities of CPT-11 and the underlying mechanisms using several in vivo and in vitro models. Diarrhea, intestinal lesions, cytokine expression, and intestinal epithelial apoptosis were monitored. Coadministered thalidomide (100 mg/kg i.p. for 8 days) significantly attenuated body weight loss, myelosuppression, diarrhea, and intestinal histological lesions caused by CPT-11 (60 mg/kg i.v. for 4 days). This was accompanied by inhibition of tumor necrosis factor-alpha, interleukins 1 and 6 and interferon-gamma, and intestinal epithelial apoptosis. Coadministered thalidomide also significantly increased the systemic exposure of CPT-11 but decreased that of SN-38 (7-ethyl-10-hydroxycampothecin). It significantly reduced the biliary excretion and cecal exposure of CPT-11, SN-38, and SN-38 glucuronide. Thalidomide hydrolytic products inhibited hydrolysis of CPT-11 in rat liver microsomes but not in primary rat hepatocytes. In addition, thalidomide and its major hydrolytic products, such as phthaloyl glutamic acid (PGA), increased the intracellular accumulation of CPT-11 and SN-38 in primary rat hepatocytes. They also significantly decreased the transport of CPT-11 and SN-38 in Caco-2 and parental MDCKII cells. Thalidomide and PGA also significantly inhibited P-glycoprotein (PgP/MDR1), multidrug resistance-associated protein (MRP1)- and MRP2-mediated CPT-11 and SN-38 transport in MDCKII cells. These results provide insights into the pharmacodynamic and pharmacokinetic mechanisms for the protective effects of thalidomide against CPT-11-induced intestinal toxicity.
... LI Zheng-qiang 1* * , LI Xiao-yuan1 , SHEU Fwu-shan2, CHEN Dong-ming 1 and YU Nai-teng 1 ( 1 ... more ... LI Zheng-qiang 1* * , LI Xiao-yuan1 , SHEU Fwu-shan2, CHEN Dong-ming 1 and YU Nai-teng 1 ( 1 Department of Chemistry, 2 Department of Biochemistry, H ong K ong University of Science & T echnology, H ong K ong ) (Received April 4, 1997) ...
Microchim Acta (2008) 162: 235243 DOI 10.1007/s00604-007-0882-0 Printed in The Netherlands ... E... more Microchim Acta (2008) 162: 235243 DOI 10.1007/s00604-007-0882-0 Printed in The Netherlands ... Electrocatalytic oxidation of methanol on a platinum modified carbon nanotube electrode ... Ying Wen1,2, Jian-Shan Ye3,4, Wei-De Zhang3, Fwu-Shan Sheu4, Guo Qin Xu2
Previous correlative and interventive work from this laboratory has suggested that activation of ... more Previous correlative and interventive work from this laboratory has suggested that activation of protein kinase C (PKC) is important for the maintenance of the hippocampal long-term potentiation (LTP) response. One such study demonstrated that application of the cis- unsaturated fatty acid, oleate, a newly discovered PKC activator, could prolong the time course of LTP. The present study explored the mechanism of cis-unsaturated fatty acid action on LTP produced by perforant path stimulation. First, neither oleate application nor high- frequency stimulation alone produced a persistent change in synaptic transmission, while the 2 in conjunction did so. This suggests that oleate acts synergistically with the consequences of this stimulation to produce an enhancement of the LTP response. Second, oleate enhancement of LTP was more potent when applied in the perforant path synaptic terminal zone than in the dentate hilus, implying that the site of oleate action is at the synapse (where PK...
Platinum nanoparticles were electrochemically deposited onto highly oriented pyrolitic graphite (... more Platinum nanoparticles were electrochemically deposited onto highly oriented pyrolitic graphite (HOPG) from H2PtCl6 solutions and observed by tapping mode atomic force microscopy. Spontaneous Pt deposition, which resulted in a wide particle size distribution, would occur on HOPG at open-circuit potential but could be suppressed by using anodic bias of the substrate before and after deposition. Nanoparticles with a narrow size distribution could be obtained when spontaneous reduction was avoided. Pt nucleated both at step edges and on terraces, with a preference for the former. The density of Pt nanoparticles on HOPG was 109–1010cm−2. Increasing the deposition overpotential or adding HCl as supporting electrolyte resulted in more uniform particles and less aggregation. These findings confirm previous results obtained by our group using only electrochemical methods [G. Lu, G. Zangari, J. Phys. Chem. B 109 (2005) 7998].
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