Cite this: DOI: 10.1039/x0xx00000x

Received 00th January 2012,

Accepted 00th January 2012

DOI: 10.1039/x0xx00000x

Nanotechnology to the Future of Biotechnology: Electrophysiology within Cells and Tissues

Pengxiang Zuo 11070161 University of Limerick

ABSTRACT

Electrophysiology monitor the electrical activity within a cell or a tissue. By gathering these data, researchers could treat and diagnose patients with risks and plans being evaluated accordingly. Nanotechnology overcome several shortcomings of conventional detection methods and provide a more stable and sensitive measurement by minimising the size of the device as well as constructing 3-D structure on flexible substrate. This paper covers recent developments in electrophysiological nano-based devices.

Journal NameRSCPublishing

Communication

ARTICLEJournal Name

Journal NameARTICLE

This journal is The Royal Society of Chemistry 2013J. Name., 2013, 00, 1-3 | 1

2 | J. Name., 2012, 00, 1-3This journal is The Royal Society of Chemistry 2012

This journal is The Royal Society of Chemistry 2012J. Name., 2012, 00, 1-3 | 2

Introduction

Nanotech is becoming increasingly important to electrophysiology, which is the study of electrical properties of biological cells and tissues. It measures voltage change and electrical currents particularly within a cell, especially those in the brain and the heart. Scientists take special interests in the electrical activity of neurons and cardiac cells because they believe it could help evaluate the effects of brain disease on neuronal functioning and evaluate electrocardiograms, assess risk of developing arrhythmias in the future[1]. This is important to diagnosing and treating the patient with relevant disease.

Conventional electrophysiology methods mainly place various electrodes such as single or arrays of needles that are used as conductors into biological tissue. With the electrode being small enough, it is possible to insert them into a single cell to monitor or observe its electrical activity, typically membrane potential. A typical intracellular recording method is current clamp, which generally inject a current into a cell via the electrodes then measure the membrane potential. In this method, the cells reactivity to electrical stimulation could be studied thus enabling scientist to understand cells especially neurotransmitters mechanism which involves the closing and opening of ionic channels that are embedded in the cell membrane[2]. However, such intracellular methods are generally invasive and are known to cause penetration to the membrane and leakage to the substance. Moreover, it is hard to record for long duration because the contacts between the electrode and the cells are hard to maintain. Other methods such as patch clamp pipettes also has problems in mechanical instability and low instability[3].

Hence, as scientist expected, the theme of making things small in Nanotechnology coincides with the need of modern

electrophysiology. This makes nanomaterial a very strong and suitable companion for electrophysiology. Nanomaterial such as nanotubes, nanowires and two dimensional nanosheets have become an increasingly hot candidate to manufacture the recording devices that are meant to be small. Whats more, the nanostructure nowadays could be specifically designed and prepared with great precision and complexity. Therefore, scientist have made unprecedented breakthrough in joining these two discipline for in the fields of biology and medicine.

In this paper, the developments of the nano-based device or technique in electrophysiology will be reviewed.

Nanomaterial Field-Effect Transistor Devices

In a field-effect transistor (FET), the shape and the conductance of a channel where a specific type of carrier flow through can be manipulated by applying an electric filed onto it. In a standard FET, current flows into the semiconductor path that is known as the channel via a source electrode and got collected at the drain electrode that locates at the other end of the semiconductor. A gate electrode is used to modulate the effective electrical diameter of the channel which in turns change the conductance of the semiconductor. A small change in gate voltage can cause a large variation in the current from the source to the drain. By applying a positive or negative gate voltage, it will deplete or accumulate carriers and thus reduce or increase the conductance.[4]

Nanomaterial such as semiconductor nanowire (NW) and carbon nanotube is known to be a suitable material for FET device .In a nanobased FET device, the nanomaterial is placed on an insulating substrate surface while making source and drain contacts to the NW or NT ends. [5]Because of nature of the hollow cylinder nanotube, the current that flows in the channel is in direct contact with the cell environment. In terms of NW device, compared with a traditional FET device, substance that binds to the surface would cause a great change to the conductance because it would influence the entire cross section of the channel instead of a small region at the surface. In other words, the above properties along with the extremely high surface-to-volume ratios of these devices make them extremely sensitive to species absorbed on the surfaces, thus making them perfect candidates for monitoring electrical activity within a cell[6].

Nanomaterial Electrical Device Monitor Tissue

Nanowire-FET device can also be utilised to record the activity of a whole organ. Compared with conventional methods, such as macroscale metallic electrodes, microscopy, dyed tissue[6], nanowire and nanotube device arrays can be fabricated into 3-D shapes that conform to the curved surface of the organ. That is to say, the disadvantages of conventional method such as low resolution due to its planar structure can be avoided.

In a study that is published in 2007, electrical recordings from whole embryonic chicken hearts were recorded using planar NWFET device. The results shows a close temporal correlation between peaks, with 100 ms consistent time difference between pipette and NW peaks due to the fact that the pipette was inserted into a spatially remote region with respect to the NWFET devices[7]. The chip that is used in this study exhibit strong endurance and can be reused for multiple times. With the NWFET device being able to wrap closely around the organ, this increase the contact area and hence and hence the sensitivity[6].

Carbon Nanopipettes

Scientist also used carbon nanopipettes (CNPs) as ohmic nanoelectrodes for intracellular recording of single cell. CNPs recorded the electrical responses of cells to pharmacological agents, the values of which matched well with predictions from the Nernst equation. CNP are known to have the advantages as they are less likely to break and clog compared with conventional method as well as multifunctional cell probing.[8]

Conclusion

It is shown that NW and NT based devices are powerful tools in electrophysiological study targeting cells or tissues. With their high sensitivity and resolution compared with conventional method, evidently nanomaterial will be increasingly important to

Biochemical research, disease diagnosis, pharmaceuticals developing.

References

1 Quinonez, D. (1998). Common applications of electrophysiology (EEG) in the past and today: the technologist's view. Electroencephalography and Clinical Neurophysiology, 106(2), pp.108-112.

2 Brennecke, R. (1974). Theory of a membrane-voltage clamp with discontinuous feedback through a pulsed current clamp. Rev. Sci. Instrum., 45(2), p.184.

3 Galvn-Hernndez, A. and Ortega-Blake, I. (2015). Improved Protocol for the Hydrophobization of Glass Pipettes for Use in Patch-Clamp Experiments; Tera-Seals and Tenths of Fa Noise. Biophysical Journal, 108(2), p.173a.

4 Li, J., Pud, S., Mayer, D. and Vitusevich, S. (2014). Advanced fabrication of Si nanowire FET structures by means of a parallel approach. Nanotechnology, 25(27), p.275302.

5 Gubbala, S., Thangala, J. and Sunkara, M. (2007). Nanowire-based electrochromic devices. Solar Energy Materials and Solar Cells, 91(9), pp.813-820.

6 Kwiat, M., Stein, D. and Patolsky, F. (2013). Nanotechnology meets electrophysiology. Current Opinion in Biotechnology, 24(4), pp.654-663.

7 Javey, A., Nam, Friedman, R., Yan, H. and Lieber, C. (2007). Layer-by-Layer Assembly of Nanowires for Three-Dimensional, Multifunctional Electronics. Nano Letters, 7(3), pp.773-777.

8 Schrlau, M., Dun, N. and Bau, H. (2009). Cell Electrophysiology with Carbon Nanopipettes. ACS Nano, 3(3), pp.563-568.