Miniaturized pH Sensors Based on Zinc Oxide Nanotubes/Nanorods

ZnO nanotubes and nanorods grown on gold thin film were used to create pH sensor devices. The developed ZnO nanotube and nanorod pH sensors display good reproducibility, repeatability and long-term stability and exhibit a pH-dependent electrochemical potential difference versus an Ag/AgCl reference electrode over a large dynamic pH range. We found the ZnO nanotubes provide sensitivity as high as twice that of the ZnO nanorods, which can be ascribed to the fact that small dimensional ZnO nanotubes have a higher level of surface and subsurface oxygen vacancies and provide a larger effective surface area with higher surface-to-volume ratio as compared to ZnO nanorods, thus affording the ZnO nanotube pH sensor a higher sensitivity. Experimental results indicate ZnO nanotubes can be used in pH sensor applications with improved performance. Moreover, the ZnO nanotube arrays may find potential application as a novel material for measurements of intracellular biochemical species within single living cells

Human Embryonic Stem Cells Derived by Somatic Cell Nuclear Transfer

SummaryReprogramming somatic cells into pluripotent embryonic stem cells (ESCs) by somatic cell nuclear transfer (SCNT) has been envisioned as an approach for generating patient-matched nuclear transfer (NT)-ESCs for studies of disease mechanisms and for developing specific therapies. Past attempts to produce human NT-ESCs have failed secondary to early embryonic arrest of SCNT embryos. Here, we identified premature exit from meiosis in human oocytes and suboptimal activation as key factors that are responsible for these outcomes. Optimized SCNT approaches designed to circumvent these limitations allowed derivation of human NT-ESCs. When applied to premium quality human oocytes, NT-ESC lines were derived from as few as two oocytes. NT-ESCs displayed normal diploid karyotypes and inherited their nuclear genome exclusively from parental somatic cells. Gene expression and differentiation profiles in human NT-ESCs were similar to embryo-derived ESCs, suggesting efficient reprogramming of somatic cells to a pluripotent state.PaperCli

Bending flexibility, kinking, and buckling characterization of ZnO nanorods/nanowires grown on different substrates by high and low temperature methods

Nanomechanical tests of bending flexibility, kinking, and buckling failure characterization of vertically aligned single crystal ZnO nanorods/nanowires were performed quantitatively by nanoindentation technique. These nanostructures were grown by the vapor liquid solid (VLS) method, a relatively high temperature approach, and the aqueous chemical growth (ACG) method, a relatively low temperature approach on different substrates, including SiC and Si. The first critical load at the inflection point found for the ZnO nanorods/nanowires grown by ACG method was 105 mu N on the SiC substrates and 114 mu N on the Si substrates. The corresponding buckling energies calculated from the force-displacement curves were 3.15x10(-12) and 2.337x10(-12) J, respectively. Similarly, for the samples grown by the VLS method, the first critical load at the inflection point and the corresponding buckling energies were calculated from the force-displacement curves as 198 mu N and 7.03x10(-12) J on the SiC substrates, and 19 mu N and 1.805x10(-13) J on the Si substrates. Moreover, the critical buckling stress, strain, and strain energy were also calculated for all samples. The strain energy for all samples was much less than the corresponding buckling energy. This shows that our as-grown samples are elastic and flexible. The elasticity measurement was performed for all the samples before reaching the first critical and kinking inflection point, and we subsequently observed the bending flexibility, kinking, and buckling phenomena on the same nanorods/nanowires. We observed that the loading and unloading behaviors during the bending test of the as-grown samples were highly symmetrical, and also that the highest point on the bending curves and the first inflection and critical point were very close. ZnO nanorods/nanowires grown on SiC by the ACG method, and those grown by the VLS method on Si substrates, show a linear relation and high modulus of elasticity for the force and displacement up to the first inflection and critical point. The results also show that the elasticity of the ZnO single crystal is approximately linear up to the first inflection point, is independent of the growth method and is strongly dependent on the verticality on the surface of the substrates. In addition, the results show that after the first buckling point, the nanorods/nanowires have plasticity, and become more flexible to produce multiple kinks.Original Publication:Riaz Muhammad, Alimujiang Fulati, Lili Yang, O Nour, Magnus Willander and P Klason , Bending flexibility, kinking, and buckling characterization of ZnO nanorods/nanowires grown on different substrates by high and low temperature methods, 2008, JOURNAL OF APPLIED PHYSICS, (104), 10, 104306-.http://dx.doi.org/10.1063/1.3018090Copyright: American Institute of Physicshttp://www.aip.org

Intracellular K(+) Determination With a Potentiometric Microelectrode Based on ZnO Nanowires

The fabrication and application of an intracellular K(+)-selective microelectrode is demonstrated. ZnO nanowires with a diameter of 100-180 nm and a length of approximately 1.5. m are grown on a borosilicate glass microcapillary. The ZnO nanowires were coated by a K(+)-ionophore-containing membrane. The K(+)-selective microelectrode exhibited a K(+)-dependent potentiometric response versus an Ag/AgCl reference microelectrode that was linear over a large concentration range (25 . M-125 mM) with a minimum detection limit of 1 . M. The measured K(+) concentrations in human adipocytes and in frog oocytes were consistent with values of K(+) concentrations reported in the literature. The sensor has several advantages including ease of fabrication, ease of insertion into the cells, low cost, and high selectivity features that make this type of sensor suitable to characterize physiologically relevant ions within single living cells.©2011 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. Syed Usman Ali, Muhammad Asif, Alimujiang Fulati, Omer Nur, Magnus Willander, Cecilia Brännmark, Peter Strålfors, Ulrika Englund, Fredrik Elinder and Bengt Danielsson, Intracellular K(+) Determination With a Potentiometric Microelectrode Based on ZnO Nanowires, 2011, IEEE transactions on nanotechnology, (10), 4, 913-919. http://dx.doi.org/10.1109/TNANO.2010.2089696</p

An intracellular glucose biosensor based on nanoflake ZnO

In this study, an improved potentiometric intracellular glucose biosensor was fabricated with immobilization of glucose oxidase on a ZnO nanoporous material. The ZnO nanoporous material with a wall thickness around 200 nm was grown on the tip of a borosilicate glass capillary and used as a selective intracellular glucose sensor for the measurement of glucose concentrations in human adipocytes and frog oocytes. The results showed a fast response within 4 s and a linear glucosedependent electrochemical response over a wide range of glucose concentration (500 nM-10 mM). The measurements of intracellular glucose concentrations with our biosensor were consistent with the values of intracellular glucose concentrations reported in the literature. The sensor also demonstrated its capability by detecting an increase in the intracellular glucose concentration induced by insulin. We found that the ZnO nanoporous material provides sensitivity as high as 1.8 times higher than that obtained using ZnO nanorods under the same conditions. Moreover, the fabrication method in our experiment is simple and the excellent performance of the developed nanosensor in sensitivity, stability, selectivity, reproducibility and anti-interference was achieved. All these advantageous features of this intracellular glucose biosensor based on functionalised ZnO nanoporous material compared to ZnO nanorods demonstrate a promising way of enhancing glucose biosensor performance to measure reliable intracellular glucose concentrations within single living cells.Original Publication:Alimujiang Fulati, Syed M. Usman Ali, Muhammad H. Asif, Naveed Ul Hassan Alvi, Magnus Willander, Cecilia Brännmark, Peter Strålfors, Sara I. Börjesson and Fredrik Elinder, An intracellular glucose biosensor based on nanoflake ZnO, 2010, Sensors and actuators. B, Chemical, (150), 2, 673-680.http://dx.doi.org/10.1016/j.snb.2010.08.021Copyright: Elsevier Science B.V., Amsterdam.http://www.elsevier.com/</p

N.B.: When citing this work, cite the original article. Original Publication:

In this study, a potentiometric intracellular glucose biosensor was fabricated by immobilization of glucose oxidase on nanoflake ZnO. Nanoflake ZnO with a wall thickness around 200 nm was grown on the tip of a borosilicate glass capillary and used as a selective intracellular glucose biosensor for the measurement of glucose concentrations in human adipocytes and frog oocytes. The results showed a fast response within 4 s and a logarithmic linear glucose-dependent electrochemical potential difference over a wide range of glucose concentration (500 nM-10 mM). Our measurements of intracellular glucose were consistent with the values of intracellular glucose concentrations reported in the literature. The monitoring capability of the sensor was demonstrated by following the increase in the intracellula