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Studies on Calcium Ion Selectivity of ZnO Nanowire Sensors Using Ionophore Membrane Coatings
Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology. (physical electronics (Magnus Willander))
Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.ORCID iD: 0000-0001-6235-7038
Department of Pure and Applied Biochemistry, Lund University, P.O. Box 124, 221 00 Lund, Sweden.
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2008 (English)In: Research Letters in Nanotechnology, ISSN 1687-6849, Vol. 2008, no Article ID 701813Article in journal (Refereed) Published
Abstract [en]

Zinc oxide nanorods with 100nm diameter and 900nm length were grown on the surface of a silver wire (0.25mm in diameter)

with the aim to produce electrochemical nanosensors. It is shown that the ZnO nanorods exhibit a Ca2+-dependent electrochemical

potentiometric behavior in an aqueous solution. The potential difference was found to be linear over a large logarithmic

concentration range (1 μM to 0.1 M) using Ag/AgCl as a reference electrode and the response time was less than one minute.

In order to adapt the sensors for calcium ion measurements in biological fluids with sufficient selectivity and stability, plastic

membrane coatings containing ionophores were applied. These functionalized ZnO nanorods sensors showed a high sensitivity

(26.55 mV/decade) and good stability.

Place, publisher, year, edition, pages
Hindawi Publishing Corporation , 2008. Vol. 2008, no Article ID 701813
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-19514DOI: 10.1155/2008/701813OAI: oai:DiVA.org:liu-19514DiVA: diva2:225277
Available from: 2009-06-25 Created: 2009-06-25 Last updated: 2014-01-15Bibliographically approved
In thesis
1. Electrochemical Biosensors Based on Functionalized Zinc Oxide Nanorods
Open this publication in new window or tab >>Electrochemical Biosensors Based on Functionalized Zinc Oxide Nanorods
2009 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The semi-conductor zinc oxide (ZnO), a representative of group II-VI has gained substantial interest in the research community due to its novel properties and characteristics. ZnO a direct band gap (3.4eV) semi-conductor has a stable wurtzite structure. Recently ZnO have attracted much interest because of its unique piezoelectric, semiconducting, catalytic properties and being biosafe and biocompatible morphology combined with the easiness of growth. This implies that ZnO has a wide range of applications in optoelectronics, sensors, transducers, energy conversion and medical sciences. This thesis relates specifically to biosensor technology and pertains more particularly to novel biosensors based on multifunctional ZnO nanorods for biological, biochemical and chemical applications.

The nanoscale science and engineering have found great promise in the fabrication of novel nano-biosensors with faster response and higher sensitivity than of planar sensor configurations. This thesis aims to highlight recent developments in materials and techniques for electrochemical biosensing, design, operation and fabrication. Rapid research growths in biomaterials, especially the availability and applications of a vast range of polymers and copolymers associated with new sensing techniques have led to remarkable innovation in the design and fabrication of biosensors. Specially nanowires/nanorods and due to their small dimensions combined with dramatically increased contact surface and strong binding with biological and chemical reagents will have important applications in biological and biochemical research. The diameter of these nanostructures is usually comparable to the size of the biological and chemical species being sensed, which intuitively makes them represent excellent primary transducers for producing electrical signals. ZnO nanostructures have unique advantages including high surface to volume ratio, nontoxicity, chemical stability, electrochemical activity, and high electron communication features. In addition, ZnO can be grown as vertical nanorods and has high ionic bonding (60%), and they are not very soluble at biological pH-values. All these facts open up for possible sensitive extra/intracellular ion measurements. New developments in biosensor design are appearing at a high rate as these devices play increasingly important roles in daily life. In this thesis we have studied calcium ion selectivity of ZnO nanorods sensors using ionophore membrane coatings in two research directions: first, we have adjusted the sensor with sufficient selectivity especially for Ca2+, and the second is to have enough sensitivity for measuring Ca2+ concentrations in extra and intracellular media. The sensor in this study was used to detect and monitor real changes of Ca2+ across human fat cells and frog cells using changes in the electrochemical potential at the interface in the intracellular microenvironment.

The first part of the thesis presents extracellular studies on calcium ions selectively by using ZnO nanorods grown on the surface of a silver wire (250 μm in diameter) with the aim to produce proto-type electrochemical biosensors. The ZnO nanorods exhibited a Ca2+-dependent electrochemical potentiometric behavior in an aqueous solution. The potential difference was found to be linear over a large logarithmic concentration range (1μM to 0.1M) using Ag/AgCl as a reference electrode. To make the sensors selective for calcium ions with sufficient selectivity and stability, plastic membrane coatings containing ionophores were applied. These functionalized ZnO nanorods sensors showed a high sensitivity (26.55 mV/decade) and good stability.

In the second part, the intracellular determination of Ca2+ was performed in two types of cells. For that we have reported functionalized ZnO nanorods grown on the tip of a borosilicate glass capillary (0.7 μm in diameter) used to selectively measure the intracellular free Ca2+ concentration in single human adipocytes and frog oocytes. The sensor exhibited a Ca2+ linear electrochemical potential over a wide Ca2+ concentration range (100 nM to 10 mM). The measurement of the Ca2+ concentration using our ZnO nanorods based sensor in living cells were consistent with values of Ca2+ concentration reported in the literature.

The third and final part, presents the calcium ion detection functionalized ZnO nanorods coupled as an extended gate metal oxide semiconductor field effect transistor (MOSFET). The electrochemical response from the interaction between the ZnO nanorods and Ca2+ in an aqueous solution was coupled directly to the gate of a MOSFET. The sensor exhibited a linear response within the range of interest from 1 μM to 1 mM. Here we demonstrated that ZnO nanorods grown on a silver wire can be combined with conventional electronic component to produce a sensitive and selective biosensor.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2009. 40 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1407
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-19573 (URN)LIU-TEK-LIC-2009:15 (Local ID)978-91-7393-592-0 (ISBN)LIU-TEK-LIC-2009:15 (Archive number)LIU-TEK-LIC-2009:15 (OAI)
Presentation
2009-08-20, TP1, Täppan, Campus Norrköping, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2009-06-29 Created: 2009-06-29 Last updated: 2014-01-15Bibliographically approved
2. Zinc Oxide Nanostructure Based Electrochemical Sensors and Drug Delivery to Intracellular Environments
Open this publication in new window or tab >>Zinc Oxide Nanostructure Based Electrochemical Sensors and Drug Delivery to Intracellular Environments
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The nanoscale science and nanostructure engineering have well established in the fabrication of novel electrochemical biosensors with faster response and higher sensitivity than of planar sensor configurations. Moreover nanostructures are suggested and used as efficient carrier of photosensitizers for cancerous cell treatment. The semi-conductor zinc oxide (ZnO) nanostructures have attracted much interest because of its unique piezoelectric, polar semiconducting, large surface area, catalytic properties, and being biosafe and biocompatible combined with the easiness of growth. This implies that ZnO nanostructures have a wide range of applications in optoelectronics, sensors, transducers, energy conversion and medical sciences. The aim of this study is to highlight recent developments in materials and techniques for electrochemical biosensing, photodynamic therapy, design, operation, and fabrication. The sensors in this study were used to detect and monitor real changes of metal ions and glucose across human fat cells and frog cells using changes in the electrochemical potential at the interface to the intracellular microenvironments. This thesis relates specifically to “zinc oxide nanostructure based electrochemical sensors and drug delivery to intracellular environments” for biological, biochemical and chemical applications.

The first part of the thesis presents extra and intracellular studies on metal ions such as Ca2+, Mg2+, and Na+…..etc selectively sensed by using ZnO nanorods grown on the tip of a borosilicate glass capillary (0.7 μm in diameter) with the aim to produce proto-type electrochemical extra/intracellular biosensors. The single human adipocyte and frog oocyte cells were used to selectively measure the intracellular free metal ions concentration. To make the sensors selective for metal ions with sufficient selectivity and stability, plastic membrane coatings containing specific ionophores were applied. These functionalized ZnO nanorods sensors showed high sensitivity and good stability with linear electrochemical potential versus a wide metal ion concentration range of interest. The measured intracellular values were consistent with values reported in the literature. Furthermore we have successfully determined that the intracellular potassium (K+) concentration decrease is not obligatory for apoptosis. The aim of this study is to show the possibility of using K+ selective microelectrode to detect and monitor intracellular changes of K+ concentration during injection of various test solution and chemically induced apoptosis in Xenopus laevis oocytes parallel with electrophysiological measurements to verify the accuracy.

The second part, presents the calcium ion (Ca2+) detection using functionalized ZnO nanorods attached as an extended gate metal oxide semiconductor field effect transistor (MOSFET). The electrochemical response was coupled directly to the gate of a commercial MOSFET to study the I-V characterization. Here we verified that ZnO nanorods grown on any thin wire can be combined with conventional electronic component to produce a sensitive and selective biosensor.

In the third part, we have performed the experiment to determine glucose concentration intracellularly and in airway surface liquid (ASL) with functionalized ZnO nanorod-coated microelectrodes. In this study, the GOD enzyme was immobilised electrostatically, drawing on the fact that there is a large difference in the isoelectric points of ZnO and glucose oxidase. Insulin has been found to affect the glucose uptake in human adipocytes and frog Xenopus laevis. The large size of these cells makes it possible to microinject specific reagents that interrupt or activate signal transmission to glucose. The measured glucose concentration in human adipocytes or frog oocytes and ASL using our ZnO nanorod sensor was consistent with values of glucose concentration reported in the literature by using other indirect techniques.

The fourth and final part covers the application of ZnO nanorods to cancer cells for photodynamic therapy. The ZnO nanorods were conjugated with protoporphyrin for local mediated photochemistry and efficient treatment of a single cancer cell. The ZnO nanorods were used as an efficient photosensitizer carrier system and at the same time providing intrinsic white light to achieve necrosis of the cancer cell. Breast cancer cells were used to study the catalytic effect of ZnO for treatment. The grown ZnO nanorods were conjugated with protoporphyrin dimethyl ester (PPDME), which absorbs the light emitted by the ZnO nanorods and cause the cytotoxicity which appears to involve the generation of reactive singlet oxygen inside the cell.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2011. 64 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1376
Keyword
ZnO nanorods, Intracellular electrochemical sensor, Functionalization, Metal ions, Glucose, Human Adipocytes, Frog Oocytes, Airway surface liquid
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-68856 (URN)978-91-7393-142-7 (ISBN)
Public defence
2011-09-02, K3, Kåkenhus, Campus Norrköping, Linköpings universitet, Norrköping, 10:15 (English)
Opponent
Supervisors
Available from: 2011-06-08 Created: 2011-06-08 Last updated: 2014-01-15Bibliographically approved

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Asif, MuhammadNour, OmerWillander, Magnus

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