The authors would like to acknowledge NanoVentures Australia for travel funding support and Prof. John Haycock for having partially hosted this research at the University of Sheffield and Ms. Jaimee Mayne for her help during the filming.

1. Au NRs Preparation
Note: Au NRs can be synthesized by a number of recipes16, or purchased from commercial vendors.
<ol>
	<li>Measure the initial optical density (OD) of the Au NR solution via UV-Vis spectroscopy, by recording the absorption values from 300 nm to 1,000 nm with a resolution of 0.5-2 nm. Vary the volume of the solution to be used with the available cuvette.</li>
	<li>Evaluate the initial NP molar concentration with a suitable technique17 (e.g. UV-Vis spectroscopy, single particle inductively coupled plasma mass spectrometry, transmission electron microscopy) or use the concentration values provided by the vendor.</li>
	<li>Prepare a 5 ml stock solution by diluting the initial Au NR sample to reach an OD = 1. For the best repeatability, keep the OD constant for all of the tested samples. Follow the commercial vendor&#8217;s protocol for the composition of the diluting solvent. If unsure, use deionized water.</li>
	<li>Centrifuge 1 ml of the Au NR solution twice for 15 min at 7,800 x g to remove any chemical excess from the solution. Centrifugation cycles can vary in force and time (e.g. 20 min at 5,600 &#215; g)18.</li>
	<li>Remove the supernatants and re-suspend the NRs in deionized water. As re-suspended particles might form aggregates in solution, prepare them daily to have the best results. Alternatively, store in a fridge for no longer than 1 week. Do not freeze.</li>
	<li>Before using under cell culture conditions, sonicate the Au NR solution for 5 min and then sterilize with UV light for 30 min (UV radiation intensity not less than 400 mW&#8729;m-2 at 254 nm).</li>
</ol>
2. NG108-15 Neuronal Cell Line Culture and Differentiation
<ol>
	<li>For the cell culture medium, prepare 500 ml of sterile Dulbecco&#39;s modified Eagle medium (DMEM) containing 10% (w/v) fetal calf serum (FCS), 1% (w/v) L-glutamine, 1% (w/v) penicillin/streptomycin and 0.5% (w/v) amphotericin B. 
	Note: Supplements can be aliquoted, stored at -20 &#176;C and added to the media on the day required. Cell culture medium can be refrigerated in a sterile condition for a maximum of 1 month.</li>
	<li>For the cell differentiation medium, prepare 50 ml of sterile DMEM containing 1% (w/v) L-glutamine, 1% (w/v) penicillin/streptomycin and 0.5% (w/v) amphotericin B.</li>
	<li>Grow NG108-15 neuronal cells in 10 ml of cell culture medium in T75 flasks made of polystyrene in an incubator with humidified atmosphere (5% CO2 at 37 &#176;C). Normally, seed 1.5-2 &#215; 105 cells in each flask to be ready in 3-4 days. Change cell culture medium every two days. 
	Note: To prevent genetic drifts or variation, do not use cells older than passage 21 for experiments.</li>
	<li>When 70-80% confluent in culture, change the medium with warm fresh cell culture medium. Mechanically detach the cells by gently knocking the bottom of the confluent flask. Do not use trypsin.</li>
	<li>Centrifuge the cell suspension for 5 min&#160;at 600 x g and re-suspend the cell pellet in 2 ml of warm cell differentiation medium.</li>
	<li>Seed 2 &#215; 104 cells/cm2 in a tissue culture polystyrene 96 well plate with 200 &#181;l of cell differentiation medium. Incubate the experiment for 1 day at 5% CO2/37 &#176;C.</li>
	<li>Add between 3.2 &#215; 109-4.2 &#215;1 010 particles/ml of Au NR solution on day 2 and incubate it for additional 24 hr. Do not add the particles for the control experiments. 
	Note: As an alternative control, Au NPs with a well-differentiated peak absorption wavelength can be used for comparison purposes14. For a more consistent cell behavior, keep the cell density constant and do not modify the well&#160;surface prior to cell seeding.</li>
</ol>
3. Neurite Outgrowth Enhancement
<ol>
	<li>Couple the laser with a single mode optical fiber (numerical aperture = 0.13) and terminate it with a fiber connector (FC connectors are convenient and commonly available). Measure the output laser power with a standard power meter. To obtain the most effective results, match the peak wavelength of the laser to the plasmon resonance peak of the NRs.</li>
	<li>On day 3 following NR incubation, fix the FC connector to the well. Irradiate samples and controls at RT for 1 min&#160;in continuous wave, for different laser powers. Allow the culture to proceed for 3 additional days at 5% CO2/37 &#176;C. Repeat the laser irradiation for a minimum of 3 independent measurements. 
	Note: Different irradiation times and pulse frequencies may be selected, depending on the application.</li>
	<li>Characterize the laser in terms of beam diameter and laser irradiance (W&#8729;cm-2).
	<ol>
		<li>For a standard single mode fiber, use NA = n&#8729;sin&#952;, where n is the refractive index of the medium in use and &#952; is the half-angle of the cone of light exiting the fiber (see Figure 1A). From trigonometry, r = tan&#952;&#8729;d, where r is the beam radius and d is the distance between the fiber and the sample. The FC connector matches the diameter of the well, therefore illuminating the sample at a distance d = 2.70 &#177; 0.20 mm. Light exits the fiber in water (n = 1.33), giving r = tan(sin-1(NA/n))&#8729;d.</li>
		<li>Using the latter equation, calculate the laser beam radius, the corresponding beam area and the average laser irradiance (laser power divided by beam area) at the target (see the example graph in Figure 1B). These values represent the average irradiance over the illuminated area.</li>
		<li>Evaluate the errors for the measurements with the general theory of error propagation. 
		Note: The distance between the FC connector and the sample can be measured by photographs of the experimental arrangement and post-processing of the image using appropriate software (e.g. ImageJ).</li>
	</ol>
	</li>
	<li>At day 5, remove cell differentiation medium from the experiments and fix the samples with 3.7% (v/v) formaldehyde solution for 10 min, then permeabilize the cells with 0.1% (v/v) Triton X-100 for 20 min.</li>
	<li>Add 3% (w/v) bovine serum albumin (BSA) to the samples for 60 min to block the unreacted protein binding sites. Label the samples for anti-&#946;III-tubulin overnight (5 &#181;g/ml in PBS supplemented with 1% of BSA) at 4 &#176;C.</li>
	<li>Incubate the cells for 90 min in the dark with an appropriate secondary antibody (e.g. TRITC-conjugated anti-mouse IgG antibody) using a concentration of 0.4-2 &#181;g/ml in 1% BSA in PBS. Label the cell nuclei with DAPI (0.1 &#181;g/ml in de-ionized water) for 10 min. 
	Note: Antibody conjugation and concentration might vary according to the company protocol. Wash samples with PBS twice for 5 min&#160;after each staining stage. 
	<img alt="Figure 1" src="/files/ftp_upload/52566/52566fig1.jpg" /></li>
	<li>Image samples by epifluorescence or confocal microscopy using at least a 20&#215; objective. Choose the microscope filters accordingly to the secondary antibody. Select a DAPI filter (&#955;EX = 358 nm; &#955;EM = 488 nm) to visualize the cell nuclei.</li>
	<li>Analyze the pictures by assessing: i) the maximum neurite length (record the length from the tip of the neurite to the beginning of the cell body), ii) the number of neurites per neuronal cell (sum up all of the neurites per cell) and iii) the percentage of cells with neurites (divide the total number of cells expressing &#946;III-tubulin by the total number of cells with a positively stained nucleus)19.</li>
</ol>
4. Laser-induced Intracellular Ca2+&#160;Imaging
<ol>
	<li>Prepare a 20% (w/v) stock solution of Pluronic F-127 by dissolving 2 g of solute in 10 ml of anhydrous dimethyl sulfoxide (DMSO). Heat the solution of Pluronic F-127 at 40 &#176;C for about 20 min&#160;to increase the solubility. Prepare it in advance if stored at RT.</li>
	<li>On day 3 following NR incubation, prepare a balanced salt solution (BSS; 135 mM NaCl, 4.5 mM KCl, 1.5 mM CaCl2 , 0.5 mM MgCl2 , 5.6 mM glucose, and 10 mM HEPES, pH 7.4) and supplemented it with 5 &#181;M of Fluo-4 AM in DMSO and 0.1% (w/v) of Pluronic F-127 solution. 
	Note: BSS solution can be prepared in advance and refrigerated for a maximum of 1 month. Add the supplements (Fluo-4 AM and Pluronic F-127) on the day of the experiment.</li>
	<li>Remove cell differentiation medium and replace it with the supplemented BSS solution. To obtain the best results with an inverted confocal microscope, incubate the cells in a micro-slide well.</li>
	<li>Load NG108-15 cells with Fluo-4 AM for 30 min&#160;in the dark at 5% CO2/37 &#176;C. Following the incubation time, wash samples twice with BSS to remove any extracellular unloaded fluorophore.</li>
	<li>Couple the laser with a single mode optical fiber and cleave the tip using standard techniques. Observe the resulting tip under an optical microscope, to ensure a high-quality surface (i.e.&#160;the tip should be perpendicular to the fiber axis and flat upon microscopy inspection).
	<ol>
		<li>Measure the output laser power with a standard power meter. Insert the light delivery fiber into an optical fiber holder and affix it to a micropositioner. Refer to Brown et al.20 for more details on optical fiber preparation and positioning. 
		Caution: Follow the general rules for laser safety during the measurement of the laser power (e.g.&#160;do not look directly into laser beam, wear laser safety goggles during handling, prevent stray light exposure to other lab users).</li>
	</ol>
	</li>
	<li>Connect an oscilloscope to the portable laser to monitor the optical modulation. Use a binary signal with variable frequencies (0.5-2 Hz) and pulse lengths (20-100 msec). Connect the laser using the modulation signal as transistor-transistor logic (TTL) input for the microscope, following the setup shown in Paviolo et al.13.
	<ol>
		<li>Place the cells under an inverted confocal microscope and position the light delivery fiber 250 &#177; 50 &#181;m away from the target cell in transmission illumination mode. At this distance, use the equations presented in 3.3.1 to calculate the beam radius at the target.</li>
	</ol>
	</li>
	<li>Use an argon-ion laser (488 nm) to excite the internalized Fluo-4 AM dye (&#955;EX = 494 nm; &#955;EM = 516 nm) and the synchronized LD for the excitation of the endocytosed NRs. Perform the imaging at RT of samples and controls using at least a 40&#215; objective by collecting time-series scans with 256 &#215; 256 pixels/frame resolution in roundtrip mode with a frequency of at least 4 Hz. Perform a recording without any LD excitation to identify any argon-ion laser interference (baseline noise).</li>
	<li>Remove the background from the data using adaptively weighted penalized least-squares algorithms21. Plot the induced Ca2+ variations as a function of time. Analyze the transient peaks in the fluorescence intensity using image post-processing software by thresholding at a level three times the standard deviation of the baseline noise (3&#963;).</li>
</ol>

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P., Bezanilla, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Infrared+light+excites+cells+by+changing+their+electrical+capacitance.">Infrared light excites cells by changing their electrical capacitance.</a> Nat. Commun. 3 (736), (2012).</li><li>Roggan, A., Friebel, M., D&#246;rschel, K., Hahn, A., M&#252;ller, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optical+properties+of+circulating+human+blood+in+the+wavelength+range+400-2500+nm.">Optical properties of circulating human blood in the wavelength range 400-2500 nm.</a> J. Biomed. Opt. 4 (1), 36-46 (1999).</li><li>Byrnes, K. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Light+promotes+regeneration+and+functional+recovery+and+alters+the+immune+response+after+spinal+cord+injury.">Light promotes regeneration and functional recovery and alters the immune response after spinal cord injury.</a> Lasers Surg. Med. 36 (3), 171-185 (2005).</li><li>Wu, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=810+nm+wavelength+light:+an+effective+therapy+for+transected+or+contused+rat+spinal+cord.">810 nm wavelength light: an effective therapy for transected or contused rat spinal cord.</a> Lasers Surg. Med. 41 (1), 36-41 (2009).</li><li>Grossman, N., Schneid, N., Reuveni, H., Halevy, S., Lubart, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=780+nm+low+power+diode+laser+irradiation+stimulates+proliferation+of+keratinocyte+cultures:+involvement+of+reactive+oxygen+species.">780 nm low power diode laser irradiation stimulates proliferation of keratinocyte cultures: involvement of reactive oxygen species.</a> Lasers Surg. Med. 22 (4), 212-218 (1998).</li><li>Wong-Riley, M. T. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photobiomodulation+directly+benefits+primary+neurons+functionally+inactivated+by+toxins+-+Role+of+cytochrome+c+oxidase.">Photobiomodulation directly benefits primary neurons functionally inactivated by toxins - Role of cytochrome c oxidase.</a> J. Biol. Chem. 280 (6), 4761-4771 (2005).</li><li>Beauvoit, B., Kitai, T., Chance, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Contribution+of+the+mitochondrial+compartment+to+the+optical+properties+pf+the+rat+liver:+a+theoretical+and+practical+approach.">Contribution of the mitochondrial compartment to the optical properties pf the rat liver: a theoretical and practical approach.</a> Biophys. J. 67 (6), 2501-2510 (1994).</li></ol>

The authors have no competing interests to disclose.

The protocols outlined in this presentation describe how to culture, differentiate and optically stimulate neuronal cells using extrinsic absorbers. The NR characteristics (e.g.&#160;dimensions, shape, plasmon resonance wavelength and surface chemistry) and the laser stimulation parameters (such as wavelength, pulse length, repetition rate, etc.) can be varied to match different experimental needs. The effects on cell behavior can be monitored using standard biological assays and materials. Overall the ...

Recent studies have demonstrated that the transient heating associated with the absorption of infrared light by water (wavelength &#62;1,400 nm) can be used to induce action potentials in nerve tissue1 and intracellular calcium transients in cardiomyocytes2. The use of infrared light has raised great interest for applications in neural prostheses, due to the potential finer spatial resolution, lack of direct contact with the tissue, minimization of stimulation artifacts, and removal of the need to genetically modify the cells prior to stimulation (as required in optogenetics)1. Despite all of these benefits, recently developed thermal models suggested that the target tissue/cells may be affected by cumulative heating effects, when multiple stimulus sites and/or high repetition rates are used3,4.
In response to these challenges, researchers have recognized the potential to use extrinsic absorbers for nerve stimulation to produce more localized heating effects in the tissue. Huang et al. demonstrated this principle by using superparamagnetic ferrite nanoparticles to remotely activate the temperature-sensitive TRPV1 channels in HEK 293 cells with a radio-frequency magnetic field5. Although this technique may allow for deeper penetration (magnetic fields interact relatively weakly with tissue), the responses were only recorded over periods of seconds, rather than the millisecond durations required in bionic devices5. Similarly, Farah et al. demonstrated electrical stimulation of rat cortical neurons with black micro-particles in vitro. They showed cell-level precision in stimulation using pulse durations on the order of hundreds of &#181;s and energies in the range of &#181;J, potentially allowing for faster repetition rates6.
The use of extrinsic absorbers has also been applied to induce morphological changes in vitro. Ciofani et al. showed a ~40% increase in neuronal cell outgrowth using piezoelectric boron nitride nanotubes excited by ultrasound7. Similarly, endocytosed iron oxide nanoparticles in PC12 cells have been reported to enhance neurite differentiation in a dose-dependent manner, due to the activation of cell adhesion molecules with the iron oxide8.
Recently, the interest in extrinsic absorbers to assist neural stimulation has also focused on the use of gold nanoparticles (Au NPs). Au NPs have the ability to efficiently absorb laser light at the plasmonic peak and to dissipate it into the surrounding environment in the form of heat9. Amongst all of the available particle shapes, the optical absorption of gold nanorods (Au NRs) conveniently matches the therapeutic window of biological tissues (near infrared - NIR, wavelength between 750-1,400 nm)10. Moreover, in the context of neural stimulation, the use of Au NRs provides relatively favorable biocompatibility and a wide range of surface functionalization options11. Recent studies have shown that a stimulatory effect on differentiation can be induced after continuous laser exposures of Au NRs in NG108-15 neuronal cells12. Similarly, intracellular calcium transients were recorded in neuronal cells cultured with Au NRs after laser irradiation modulated with variable frequencies and pulse lengths13. Cell membrane depolarization was also recorded after NIR laser illumination of Au NRs in primary cultures of spiral ganglion neurons14. The first in vivo application with irradiated Au NRs has been demonstrated just recently. Eom and coworkers exposed Au NRs at their plasmonic peak and recorded a six-fold increase in the amplitude of compound nerve action potentials (CNAPs) and a three-fold decrease in the stimulation threshold in rat sciatic nerves. The enhanced response was attributed to local heating effects resulting from the excitation of the NR plasmonic peak15.
In the present paper, protocols for investigating the effects of laser stimulation in NG108-15 neuronal cells cultured with Au NRs are specified. These methods provide a simple, yet powerful, way to irradiate cell populations in vitro using standard biological techniques and materials. The protocol is based on a fiber-coupled laser diode (LD) that allows safe operation and repeatable alignment. The Au NR sample preparation and laser irradiation methods can be further extended to different particle shapes and neuronal cell cultures, providing that the specific synthesis and culture protocols are known, respectively.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>Au NR</td>
			<td>Sigma Aldrich</td>
			<td>716812</td>
			<td></td>
		</tr>
		<tr>
			<td>NG108-15</td>
			<td>Sigma Aldrich</td>
			<td>8811230</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM</td>
			<td>Sigma Aldrich</td>
			<td>D6546</td>
			<td></td>
		</tr>
		<tr>
			<td>FCS</td>
			<td>Life Technologies</td>
			<td>10100147</td>
			<td></td>
		</tr>
		<tr>
			<td>L-glutamine</td>
			<td>Sigma Aldrich</td>
			<td>G7513</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin/streptomycin</td>
			<td>Life Technologies</td>
			<td>15140122</td>
			<td></td>
		</tr>
		<tr>
			<td>Amphotericin B</td>
			<td>Life Technologies</td>
			<td>15290018</td>
			<td></td>
		</tr>
		<tr>
			<td>Formaldehyde</td>
			<td>Sigma Aldrich</td>
			<td>F8775</td>
			<td></td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>BDH</td>
			<td>T8532</td>
			<td></td>
		</tr>
		<tr>
			<td>BSA</td>
			<td>Sigma Aldrich</td>
			<td>A2058</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-&#946;III-tubulin</td>
			<td>Promega</td>
			<td>G7121</td>
			<td></td>
		</tr>
		<tr>
			<td>TRITC-conjugated anti-mouse IgG antibody</td>
			<td>Sigma Aldrich</td>
			<td>T5393</td>
			<td></td>
		</tr>
		<tr>
			<td>DAPI</td>
			<td>Invitrogen</td>
			<td>D1306</td>
			<td></td>
		</tr>
		<tr>
			<td>Fluo-4 AM</td>
			<td>Invitrogen</td>
			<td>F14201</td>
			<td></td>
		</tr>
		<tr>
			<td>DMSO</td>
			<td>Sigma Aldrich</td>
			<td>472301</td>
			<td></td>
		</tr>
		<tr>
			<td>Pluronic F-127</td>
			<td>Invitrogen</td>
			<td>P6867</td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Equipment name</td>
			<td>Company</td>
			<td>Catalogue Number</td>
			<td></td>
		</tr>
		<tr>
			<td>UV-Vis spectrometer</td>
			<td>Varian Medical Systems Inc.</td>
			<td>Cary 50 Bio</td>
			<td></td>
		</tr>
		<tr>
			<td>Mini centrifuge</td>
			<td>Eppendorf</td>
			<td>Mini Spin</td>
			<td></td>
		</tr>
		<tr>
			<td>Sonic bath</td>
			<td>Unisonics Australia</td>
			<td>FPX 10D</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell culture incubator</td>
			<td>Kendro</td>
			<td>Hera Cell 150</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell culture centrifuge</td>
			<td>Hettich</td>
			<td>Rotofix 32A</td>
			<td></td>
		</tr>
		<tr>
			<td>Laser diode</td>
			<td>Optotech</td>
			<td>780 nm single mode fibre - coupled LD</td>
			<td></td>
		</tr>
		<tr>
			<td>Optical fiber</td>
			<td>Thorlabs</td>
			<td>780 HP</td>
			<td></td>
		</tr>
		<tr>
			<td>Power meter</td>
			<td>Coherent</td>
			<td>Laser Check</td>
			<td></td>
		</tr>
		<tr>
			<td>ImageJ</td>
			<td>http://rsb.info.nih.gov/ij/index.html</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Epifluorescent microscope</td>
			<td>Axon Instruments</td>
			<td>ImageX-press 5000A</td>
			<td></td>
		</tr>
		<tr>
			<td>&#956;-slide well</td>
			<td>Ibidi</td>
			<td>80826</td>
			<td></td>
		</tr>
		<tr>
			<td>Inverted confocal microscope</td>
			<td>Carl Zeiss Microscopy Ltd.</td>
			<td>LSM 510 meta-confocal microscope</td>
			<td></td>
		</tr>
		<tr>
			<td>Oscilloscope</td>
			<td>Tektronix</td>
			<td>TDS210</td>
			<td></td>
		</tr>
	</tbody>
</table>

gold nanorod-assisted optical stimulation of neuronal cells

Recent studies have demonstrated that nerves can be stimulated in a variety of ways by the transient heating associated with the absorption of infrared light by water in neuronal tissue. This technique holds great potential for replacing or complementing standard stimulation techniques, due to the potential for increased localization of the stimulus and minimization of mechanical contact with the tissue. However, optical approaches are limited by the inability of visible light to penetrate deep into tissues. Moreover, thermal modelling suggests that cumulative heating effects might be potentially hazardous when multiple stimulus sites or high laser repetition rates are used. The protocol outlined below describes an enhanced approach to the infrared stimulation of neuronal cells. The underlying mechanism is based on the transient heating associated with the optical absorption of gold nanorods, which can cause triggering of neuronal cell differentiation and increased levels of intracellular calcium activity. These results demonstrate that nanoparticle absorbers can enhance and/or replace the process of infrared neural stimulation based on water absorption, with potential for future applications in neural prostheses and cell therapies.

By using Protocols 1, 2, and 3 described here, a stimulatory effect on differentiation was observed in NG108-15 neuronal cells cultured with Au NPs (Au NRs, poly(styrenesulfonate)-coated Au NRs and silica-coated Au NRs) after laser exposures between 1.25 and 7.5 W&#183;cm&#8722;2 . Confocal images of rhodamineB-labelled Au NRs demonstrated that the particles were internalized from day 1 of incubation12. The localization was predominantly observed in the cell cytoplasm, indicating that the preferred ...

Watch this Scientific Journal Video about Gold Nanorod-assisted Optical Stimulation of Neuronal Cells at JoVE.com

Gold Nanorod-assisted Optical Stimulation of Neuronal Cells

This protocol outlines how to use the transient heating associated with the optical absorption of gold nanorods to stimulate differentiation and intracellular calcium activity in neuronal cells. These results potentially open up new applications in neural prostheses and fundamental studies in neuroscience.

Recent studies have demonstrated that nerves can be stimulated in a variety of ways by the transient heating associated with the absorption of infrared ...

gold-nanorod-assisted-optical-stimulation-of-neuronal-cells

Research

JoVE Journal

Neuroscience

8.9K Views.  Swinburne University of Technology. This protocol outlines how to use the transient heating associated with the optical absorption of gold nanorods to stimulate differentiation and intracellular calcium activity in neuronal cells. These results potentially open up new applications in neural prostheses and fundamental studies in neuroscience.

Video: Gold Nanorod-assisted Optical Stimulation of Neuronal Cells

Combining Transcranial Magnetic Stimulation and fMRI to Examine the Default Mode Network

The default mode network is a group of brain regions that are active when an individual is not focused on the outside world and the brain is at "wakeful rest."1,2,3 It is thought the default mode network corresponds to self-referential or "internal mentation".2,3
It has been hypothesized that, in humans, activity within the default mode network is correlated with certain pathologies (for instance, hyper-activation has been linked to schizophrenia 4,5,6 and autism spectrum disorders 7 whilst hypo-activation of the network has been linked to Alzheimer's and other neurodegenerative diseases 8). As such, noninvasive modulation of this network may represent a potential therapeutic intervention for a number of neurological and psychiatric pathologies linked to abnormal network activation. One possible tool to effect this modulation is Transcranial Magnetic Stimulation: a non-invasive neurostimulatory and neuromodulatory technique that can transiently or lastingly modulate cortical excitability (either increasing or decreasing it) via the application of localized magnetic field pulses.9
In order to explore the default mode network's propensity towards and tolerance of modulation, we will be combining TMS (to the left inferior parietal lobe) with functional magnetic resonance imaging (fMRI). Through this article, we will examine the protocol and considerations necessary to successfully combine these two neuroscientific tools.

In this article, we examine the methodology and considerations relevant to the combination of TMS and fMRI to examine the effects of brain stimulation on the default network.

The default mode network is a group of brain regions that are active when an individual is not focused on the outside world and the brain is at "wakeful ...

TMS: Using the Theta-Burst Protocol to Explore Mechanism of Plasticity in Individuals with Fragile X Syndrome and Autism

Fragile X Syndrome (FXS), also known as Martin-Bell Syndrome, is a genetic abnormality found on the X chromosome.1,2 Individuals suffering from FXS display abnormalities in the expression of FMR1 - a protein required for typical, healthy neural development.3 Recent data has suggested that the loss of this protein can cause the cortex to be hyperexcitable thereby affecting overall patterns of neural plasticity.4,5
In addition, Fragile X shows a strong comorbidity with autism: in fact, 30% of children with FXS are diagnosed with autism, and 2 - 5% of autistic children suffer from FXS.6
Transcranial Magnetic Stimulation (a non-invasive neurostimulatory and neuromodulatory technique that can transiently or lastingly modulate cortical excitability via the application of localized magnetic field pulses 7,8) represents a unique method of exploring plasticity and the manifestations of FXS within affected individuals. More specifically, Theta-Burst Stimulation (TBS), a specific stimulatory protocol shown to modulate cortical plasticity for a duration up to 30 minutes after stimulation cessation in healthy populations, has already proven an efficacious tool in the exploration of abnormal plasticity.9,10 
Recent studies have shown the effects of TBS last considerably longer in individuals on the autistic spectrum - up to 90 minutes.11 This extended effect-duration suggests an underlying abnormality in the brain's natural plasticity state in autistic individuals - similar to the hyperexcitability induced by Fragile X Syndrome.
In this experiment, utilizing single-pulse motor-evoked potentials (MEPs) as our benchmark, we will explore the effects of both intermittent and continuous TBS on cortical plasticity in individuals suffering from FXS and individuals on the Autistic Spectrum.

In this article, we examine the effects of Theta-Burst TMS stimulation on cortical plasticity in individuals suffering from Fragile X syndrome and individuals on the autistic spectrum.

Fragile X Syndrome (FXS), also known as Martin-Bell Syndrome, is a genetic abnormality found on the X chromosome.1,2 Individuals suffering from FXS ...

The NeuroStar TMS Device: Conducting the FDA Approved Protocol for Treatment of Depression

The Neuronetics NeuroStar Transcranial Magnetic Stimulation (TMS) System is a class II medical device that produces brief duration, pulsed magnetic fields. These rapidly alternating fields induce electrical currents within localized, targeted regions of the cortex which are associated with various physiological and functional brain changes.1,2,3
In 2007, O'Reardon et al., utilizing the NeuroStar device, published the results of an industry-sponsored, multisite, randomized, sham-stimulation controlled clinical trial in which 301 patients with major depression, who had previously failed to respond to at least one adequate antidepressant treatment trial, underwent either active or sham TMS over the left dorsolateral prefrontal cortex (DLPFC). The patients, who were medication-free at the time of the study, received TMS five times per week over 4-6 weeks.4
The results demonstrated that a sub-population of patients (those who were relatively less resistant to medication, having failed not more than two good pharmacologic trials) showed a statistically significant improvement on the Montgomery-Asberg Depression Scale (MADRS), the Hamilton Depression Rating Scale (HAMD), and various other outcome measures. In October 2008, supported by these and other similar results5,6,7, Neuronetics obtained the first and only Food and Drug Administration (FDA) approval for the clinical treatment of a specific form of medication-refractory depression using a TMS Therapy device (FDA approval K061053).
In this paper, we will explore the specified FDA approved NeuroStar depression treatment protocol (to be administered only under prescription and by a licensed medical profession in either an in- or outpatient setting).

In this article, we examine the methodology and considerations relevant to the FDA approved depression treatment protocol using the Neuronetics NeuroStar TMS device.

The Neuronetics NeuroStar Transcranial Magnetic Stimulation (TMS) System is a class II medical device that produces brief duration, pulsed magnetic ...

Live-cell Imaging of Sensory Organ Precursor Cells in Intact Drosophila Pupae

Since the discovery of Green Fluorescent Protein (GFP), there has been a revolutionary change in the use of live-cell imaging as a tool for understanding fundamental biological mechanisms. Striking progress has been particularly evident in Drosophila, whose extensive toolkit of mutants and transgenic lines provides a convenient model to study evolutionarily-conserved developmental and cell biological mechanisms. We are interested in understanding the mechanisms that control cell fate specification in the adult peripheral nervous system (PNS) in Drosophila. Bristles that cover the head, thorax, abdomen, legs and wings of the adult fly are individual mechanosensory organs, and have been studied as a model system for understanding mechanisms of Notch-dependent cell fate decisions. Sensory organ precursor (SOP) cells of the microchaetes (or small bristles), are distributed throughout the epithelium of the pupal thorax, and are specified during the first 12 hours after the onset of pupariation. After specification, the SOP cells begin to divide, segregating the cell fate determinant Numb to one daughter cell during mitosis. Numb functions as a cell-autonomous inhibitor of the Notch signaling pathway.
Here, we show a method to follow protein dynamics in SOP cell and its progeny within the intact pupal thorax using a combination of tissue-specific Gal4 drivers and GFP-tagged fusion proteins 1,2.This technique has the advantage over fixed tissue or cultured explants because it allows us to follow the entire development of an organ from specification of the neural precursor to growth and terminal differentiation of the organ. We can therefore directly correlate changes in cell behavior to changes in terminal differentiation. Moreover, we can combine the live imaging technique with mosaic analysis with a repressible cell marker (MARCM) system to assess the dynamics of tagged proteins in mitotic SOPs under mutant or wildtype conditions. Using this technique, we and others have revealed novel insights into regulation of asymmetric cell division and the control of Notch signaling activation in SOP cells (examples include references 1-6,7 ,8).

Live-cell Imaging of Sensory Organ Precursor Cells in Intact Drosophila Pupae

In this video, we describe a method for live cell imaging of asymmetrically dividing sensory organ progenitor cells and epidermal cells in intact Drosophila pupae

Since the discovery of Green Fluorescent Protein (GFP), there has been a revolutionary change in the use of live-cell imaging as a tool for understanding ...

Optical Control of a Neuronal Protein Using a Genetically Encoded Unnatural Amino Acid in Neurons

Photostimulation is a noninvasive way to control biological events with excellent spatial and temporal resolution. New methods are desired to photo-regulate endogenous proteins expressed in their native environment. Here, we present an approach to optically control the function of a neuronal protein directly in neurons using a genetically encoded unnatural amino acid (Uaa). By using an orthogonal tRNA/aminoacyl-tRNA synthetase pair to suppress the amber codon, a photo-reactive Uaa 4,5-dimethoxy-2-nitrobenzyl-cysteine (Cmn) is site-specifically incorporated in the pore of a neuronal protein Kir2.1, an inwardly rectifying potassium channel. The bulky Cmn physically blocks the channel pore, rendering Kir2.1 non-conducting. Light illumination instantaneously converts Cmn into a smaller natural amino acid Cys, activating Kir2.1 channel function. We express these photo-inducible inwardly rectifying potassium (PIRK) channels in rat hippocampal primary neurons, and demonstrate that light-activation of PIRK ceases the neuronal firing due to the outflux of K+ current through the activated Kir2.1 channels. Using in utero electroporation, we also express PIRK in the embryonic mouse neocortex in vivo, showing the light-activation of PIRK in neocortical neurons. Genetically encoding Uaa imposes no restrictions on target protein type or cellular location, and a family of photoreactive Uaas is available for modulating different natural amino acid residues. This technique thus has the potential to be generally applied to many neuronal proteins to achieve optical regulation of different processes in brains. The current protocol presents an accessible procedure for intricate Uaa incorporation in neurons in vitro and in vivo to achieve photo control of neuronal protein activity on the molecular level.

Here, a procedure to selectively activate a neuronal protein with a short pulse of light by genetically encoding a photo-reactive unnatural amino acid into a target neuronal protein expressed in neurons in culture or in vivo is presented.

Photostimulation is a noninvasive way to control biological events with excellent spatial and temporal resolution. New methods are desired to ...

Time-dependent Increase in the Network Response to the Stimulation of Neuronal Cell Cultures on Micro-electrode Arrays

Micro-electrode arrays (MEAs) can be used to investigate drug toxicity, design paradigms for next-generation personalized medicine, and study network dynamics in neuronal cultures. In contrast with more traditional methods, such as patch-clamping, which can only record activity from a single cell, MEAs can record simultaneously from multiple sites in a network, without requiring the arduous task of placing each electrode individually. Moreover, numerous control and stimulation configurations can be easily applied within the same experimental setup, allowing for a broad range of dynamics to be explored. One of the key dynamics of interest in these in vitro studies has been the extent to which cultured networks display properties indicative of learning. Mouse neuronal cells cultured on MEAs display an increase in response following training induced by electrical stimulation. This protocol demonstrates how to culture neuronal cells on MEAs; successfully record from over 95% of the plated dishes; establish a protocol to train the networks to respond to patterns of stimulation; and sort, plot, and interpret the results from such experiments. The use of a proprietary system for stimulating and recording neuronal cultures is demonstrated. Software packages are also used to sort neuronal units. A custom-designed graphical user interface is used to visualize post-stimulus time histograms, inter-burst intervals, and burst duration, as well as to compare the cellular response to stimulation before and after a training protocol. Finally, representative results and future directions of this research effort are discussed.

Mouse neuronal cells cultured on multi-electrode arrays display an increase in response following electrical stimulation. This protocol demonstrates how to culture neurons, how to record activity, and how to establish a protocol to train the networks to respond to patterns of stimulation.

Micro-electrode arrays (MEAs) can be used to investigate drug toxicity, design paradigms for next-generation personalized medicine, and study network ...

Optical Coherence Tomography: Imaging Mouse Retinal Ganglion Cells In Vivo

Structural changes in the retina are common manifestations of ophthalmic diseases. Optical coherence tomography (OCT) enables their identification in vivo&#8212;rapidly, repetitively, and at a high resolution. This protocol describes OCT imaging in the mouse retina as a powerful tool to study optic neuropathies (OPN). The OCT system is an interferometry-based, non-invasive alternative to common post mortem histological assays. It provides a fast and accurate assessment of retinal thickness, allowing the possibility to track changes, such as retinal thinning or thickening. We present the imaging process and analysis with the example of the Opa1delTTAG mouse line. Three types of scans are proposed, with two quantification methods: standard and homemade calipers. The latter is best for use on the peripapillary retina during radial scans; being more precise, is preferable for analyzing thinner structures. All approaches described here are designed for retinal ganglion cells (RGC) but are easily adaptable to other cell populations. In conclusion, OCT is efficient in mouse model phenotyping and has the potential to be used for the reliable evaluation of therapeutic interventions.

Optical Coherence Tomography: Imaging Mouse Retinal Ganglion Cells In Vivo

This manuscript describes a protocol for the in vivo imaging of the mouse retina with high-resolution spectral domain optical coherence tomography (SD-OCT). It focuses on retinal ganglion cells (RGC) in the peripapillary region, with several scanning and quantifying approaches described.

Structural changes in the retina are common manifestations of ophthalmic diseases. Optical coherence tomography (OCT) enables their identification in ...

Chronic Transcranial Electrical Stimulation and Intracortical Recording in Rats

Transcranial electrical stimulation (TES) is a powerful and relatively simple approach to diffusely influence brain activity either randomly or in a closed-loop event-triggered manner. Although many studies are focusing on the possible benefits and side-effects of TES in healthy and pathologic brains, there are still many fundamental open questions regarding the mechanism of action of the stimulation. Therefore, there is a clear need for a robust and reproducible method to test the acute and the chronic effects of TES in rodents. TES can be combined with regular behavioral, electrophysiological, and imaging techniques to investigate neuronal networks in vivo. The implantation of transcranial stimulation electrodes does not impose extra constraints on the experimental design while it offers a versatile, flexible tool to manipulate brain activity. Here we provide a detailed, step-by-step protocol to fabricate and implant transcranial stimulation electrodes to influence brain activity in a temporally constrained manner for months.

This detailed protocol describes transcranial stimulation electrode placement on the temporal bone in order to investigate the short- and long-term effects of transcranial electrical stimulation in freely moving rats.

Transcranial electrical stimulation (TES) is a powerful and relatively simple approach to diffusely influence brain activity either randomly or in a ...

Neuronal Differentiation from Mouse Embryonic Stem Cells In vitro

The neural differentiation of mouse embryonic stem cells (mESCs) is a potential tool for elucidating the key mechanisms involved in neurogenesis and potentially aid in regenerative medicine. Here, we established an efficient and low cost method for neuronal differentiation from mESCs in vitro, using the strategy of combinatorial screening. Under the conditions defined here, the 2-day embryoid body formation + 6-day retinoic acid induction protocol permits fast and efficient differentiation from mESCs into neural precursor cells (NPCs), as seen by the formation of well-stacked and neurite-like A2lox and 129 derivatives that are Nestin positive. The healthy state of embryoid bodies and the timepoint at which retinoic acid (RA) is applied, as well as the RA concentrations, are critical in the process. In the subsequent differentiation from NPCs into neurons, N2B27 medium II (supplemented by Neurobasal medium) could better support the long term maintenance and maturation of neuronal cells. The presented method is highly efficiency, low cost and easy to operate, and can be a powerful tool for neurobiology and developmental biology research.

Here, we established a low cost and easy to operate method that directs fast and efficient differentiation from embryonic stem cells into neurons. This method is suitable for popularization among laboratories and can be a useful tool for neurological research.

The neural differentiation of mouse embryonic stem cells (mESCs) is a potential tool for elucidating the key mechanisms involved in neurogenesis and ...

GM-Free Generation of Blood-Derived Neuronal Cells

Many human&#160;neurological disorders are caused by degeneration of neurons and glial cells in the brain. Due to limitations in pharmacological and other therapeutic strategies, there is currently no cure available for the injured or diseased brain. Cell replacement appears as a promising therapeutic strategy for neurodegenerative conditions. To this day, neural stem cells (NSCs) have been successfully generated from fetal tissues, human embryonic cells (ES) or induced pluripotent stem cells (iPSC). A process of dedifferentiation was initiated by activation of the novel human GPI-linked glycoprotein, which leads to generation of pluripotent stem cells. These blood-derived pluripotent stem cells (BD-PSCs) differentiate in vitro into cells with a neural phenotype as shown by brightfield and immunofluorescence microscopy. Ultrastructural analysis of these cells by means of electron microscopy confirms their primitive structure as well as neuronal-like morphology and subcellular characteristics.

We present a genetically modified-free (GM-free) method to obtain cells with a neuronal phenotype from reprogrammed peripheral blood cells. Activation of a signaling pathway linked to novel human GPI-linked protein reveals an efficient GM-free method for obtaining human pluripotent stem cells.

Many human&#160;neurological disorders are caused by degeneration of neurons and glial cells in the brain. Due to limitations in pharmacological and other ...