Optical Neuronal Guidance

Name

Description

It has been known since 2002 that a highly focussed infrared beam can influence the rate and direction of neuronal growth[1]. In this method, a highly focussed laser spot (essentially, an optical tweezer) is focussed on the leading edge of an extending axon in order to guide its growth. This phenomenon works with 780 nm and 1064 nm laser irradiation[2]. We have demonstrated that this effect is not thermally mediated[2], but instead may be due to the photomechanical alignment of filopodia within the beam[3]. Current work is ongoing to characterise the biochemistry of this event, to explore the use of different types of guiding beam profiles such as line traps, and to automate the procedure.

Schemes and typical results

Figure 1 shows a laser guided neuron growth setup. A 780 nm or 1064 nm laser is channelled into the back aperture of a high numerical aperture objective. A coverslip-bottomed culture dish or Carrel flask [4] containing NG108 cells, serum starved to produce growth cones, is heated by Peltier to 37 ºC and kept in a hermetic atmosphere of 5% CO2. The laser is manually actuated using the steering mirror to induce a growth cone turn. Figure 2 shows this guidance in action using a 780 nm laser. This experiment lasted approximately one hour. The efficiency of guidance of extending axons is approximately 50% for both wavelengths [2].

Figure 1: The optical setup. The system used laser wavelengths of 780 nm or 1064 nm each focused to approximately the same beam spot in the sample plane. From reference [2].

Figure 2: The leading edge of an NG108 cell being optically guided using a 780 nm focussed laser.

Special features and limitations

Special Features:

• Single axon guidance

Limitations:

• Guidance is not 100% efficient
• Has not been yet demonstrated in vivo

Publications

[1] Ehrlicher, Betz, Stuhrmann, Koch, Milner, Raizen, and Kas, Proc.Natl.Acad.Sci U.S.A, 99, 16024-16028 (2002).

[2] Stevenson, Lake, Agate, Gárcés-Chávez, Dholakia, and Gunn-Moore, Opt. Express, 14, 9786-9793 (2006).

[3] Carnegie, Stevenson, Mazilu, Gunn-Moore, and Dholakia, Opt. Express, 16, 10507 (2008).

[4] Stevenson, DJ, Carnegie, D.J., Agate, B., Gunn-Moore, F., Dholakia, K., Microscopy and Analysis, 22 (1), 9-11 (2008).

What biological process are you investigating?

Axon guidance by optical cues.

What equipment do you use?

Optical tweezers. Long term on-stage incubation chambers.

What analytes do you measure?

What chemicals (fluorophores, labels, ...) do you use to measure your analytes / signatures? Or is it label free? Examples: fluorescence, Raman, SHG

Expert(s)

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