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ZnO Nanostructure-Based Intracellular Sensor.

Asif MH, Danielsson B, Willander M - Sensors (Basel) (2015)

Bottom Line: Recently ZnO has attracted much interest because of its usefulness for intracellular measurements of biochemical species by using its semiconducting, electrochemical, catalytic properties and for being biosafe and biocompatible.ZnO thus has a wide range of applications in optoelectronics, intracellular nanosensors, transducers, energy conversion and medical sciences.For intracellular measurements, the ZnO nanowires/nanorods were grown on the tip of a borosilicate glass capillary (0.7 µm in diameter) and functionalized with membranes or enzymes to produce intracellular selective metal ion or glucose sensors.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, COMSATS Institute of Information Technology, Lahore 54000, Pakistan. asifhassan@ciitlahore.edu.pk.

ABSTRACT
Recently ZnO has attracted much interest because of its usefulness for intracellular measurements of biochemical species by using its semiconducting, electrochemical, catalytic properties and for being biosafe and biocompatible. ZnO thus has a wide range of applications in optoelectronics, intracellular nanosensors, transducers, energy conversion and medical sciences. This review relates specifically to intracellular electrochemical (glucose and free metal ion) biosensors based on functionalized zinc oxide nanowires/nanorods. For intracellular measurements, the ZnO nanowires/nanorods were grown on the tip of a borosilicate glass capillary (0.7 µm in diameter) and functionalized with membranes or enzymes to produce intracellular selective metal ion or glucose sensors. Successful intracellular measurements were carried out using ZnO nanowires/nanorods grown on small tips for glucose and free metal ions using two types of cells, human fat cells and frog oocytes. The sensors in this study were used to detect real-time changes of metal ions and glucose across human fat cells and frog cells using changes in the electrochemical potential at the interface of the intracellular micro-environment. Such devices are helpful in explaining various intracellular processes involving ions and glucose.

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A calibration curve showing the electrochemical potential difference vs. the Ag/AgCl reference electrode in response to the glucose concentration using the functionalized ZnO nanorods as working electrode [3].
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sensors-15-11787-f003: A calibration curve showing the electrochemical potential difference vs. the Ag/AgCl reference electrode in response to the glucose concentration using the functionalized ZnO nanorods as working electrode [3].

Mentions: In the human body, the hormone insulin only stimulates glucose transport into muscle and fat cells. However, insulin has also been found to affect glucose uptake in oocytes from the frog Xenopus laevis [20,21]. The large size of these cells makes it possible to microinject specific reagents that interrupt or activate signal transmission to glucose. A dynamic range of glucose concentrations was made in 10 mM Phosphate Buffered Saline (PBS) containing 1.5 mM Na2HPO4, 48 mM KH2PO4, 0.135 mM sodium chloride and 2.7 mM KCl at pH 7.4. The response of the electrochemical potential difference of the ZnO nanorods vs. reference electrode to the changes in buffer electrolyte enabled glucose measurements the range of 500 nM to 1 mM and shows that the glucose dependence is linear with sensitivity equal to 42.5 mV/decade (Figure 3) [3,7]. The intracellular glucose concentration in the human adipocytes was 50 ± 15 µM (n = 5), which can be compared with the 70 µM intracellular concentration determined by nuclear magnetic resonance spectroscopy in rat muscle tissue in the presence of a high, 10 mM, extracellular glucose concentration [15]. For the frog oocytes, it was 125 ± 23 µM (n = 5). When we achieved a stable potential for the intracellular measurement, 10 nM insulin was added to the extracellular solution. After few minutes, the insulin increased the glucose concentration in the human adipocyte from 50 ± 15 to 125 ± 15 µM and the glucose concentration in the frog oocytes increased from 125 ± 23 µM to 250 ± 19 µM [3]. The reported values of the glucose concentration in human adipocytes and frog oocytes using our functionalized ZnO nanorods sensor were consistent with values of glucose concentration reported in the literature survey [3].


ZnO Nanostructure-Based Intracellular Sensor.

Asif MH, Danielsson B, Willander M - Sensors (Basel) (2015)

A calibration curve showing the electrochemical potential difference vs. the Ag/AgCl reference electrode in response to the glucose concentration using the functionalized ZnO nanorods as working electrode [3].
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4481971&req=5

sensors-15-11787-f003: A calibration curve showing the electrochemical potential difference vs. the Ag/AgCl reference electrode in response to the glucose concentration using the functionalized ZnO nanorods as working electrode [3].
Mentions: In the human body, the hormone insulin only stimulates glucose transport into muscle and fat cells. However, insulin has also been found to affect glucose uptake in oocytes from the frog Xenopus laevis [20,21]. The large size of these cells makes it possible to microinject specific reagents that interrupt or activate signal transmission to glucose. A dynamic range of glucose concentrations was made in 10 mM Phosphate Buffered Saline (PBS) containing 1.5 mM Na2HPO4, 48 mM KH2PO4, 0.135 mM sodium chloride and 2.7 mM KCl at pH 7.4. The response of the electrochemical potential difference of the ZnO nanorods vs. reference electrode to the changes in buffer electrolyte enabled glucose measurements the range of 500 nM to 1 mM and shows that the glucose dependence is linear with sensitivity equal to 42.5 mV/decade (Figure 3) [3,7]. The intracellular glucose concentration in the human adipocytes was 50 ± 15 µM (n = 5), which can be compared with the 70 µM intracellular concentration determined by nuclear magnetic resonance spectroscopy in rat muscle tissue in the presence of a high, 10 mM, extracellular glucose concentration [15]. For the frog oocytes, it was 125 ± 23 µM (n = 5). When we achieved a stable potential for the intracellular measurement, 10 nM insulin was added to the extracellular solution. After few minutes, the insulin increased the glucose concentration in the human adipocyte from 50 ± 15 to 125 ± 15 µM and the glucose concentration in the frog oocytes increased from 125 ± 23 µM to 250 ± 19 µM [3]. The reported values of the glucose concentration in human adipocytes and frog oocytes using our functionalized ZnO nanorods sensor were consistent with values of glucose concentration reported in the literature survey [3].

Bottom Line: Recently ZnO has attracted much interest because of its usefulness for intracellular measurements of biochemical species by using its semiconducting, electrochemical, catalytic properties and for being biosafe and biocompatible.ZnO thus has a wide range of applications in optoelectronics, intracellular nanosensors, transducers, energy conversion and medical sciences.For intracellular measurements, the ZnO nanowires/nanorods were grown on the tip of a borosilicate glass capillary (0.7 µm in diameter) and functionalized with membranes or enzymes to produce intracellular selective metal ion or glucose sensors.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, COMSATS Institute of Information Technology, Lahore 54000, Pakistan. asifhassan@ciitlahore.edu.pk.

ABSTRACT
Recently ZnO has attracted much interest because of its usefulness for intracellular measurements of biochemical species by using its semiconducting, electrochemical, catalytic properties and for being biosafe and biocompatible. ZnO thus has a wide range of applications in optoelectronics, intracellular nanosensors, transducers, energy conversion and medical sciences. This review relates specifically to intracellular electrochemical (glucose and free metal ion) biosensors based on functionalized zinc oxide nanowires/nanorods. For intracellular measurements, the ZnO nanowires/nanorods were grown on the tip of a borosilicate glass capillary (0.7 µm in diameter) and functionalized with membranes or enzymes to produce intracellular selective metal ion or glucose sensors. Successful intracellular measurements were carried out using ZnO nanowires/nanorods grown on small tips for glucose and free metal ions using two types of cells, human fat cells and frog oocytes. The sensors in this study were used to detect real-time changes of metal ions and glucose across human fat cells and frog cells using changes in the electrochemical potential at the interface of the intracellular micro-environment. Such devices are helpful in explaining various intracellular processes involving ions and glucose.

Show MeSH