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. ...

<ol>
	<li>Richter, C. P., Matic, A. I., Wells, J. D., Jansen, E. D., Walsh, J. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neural+stimulation+with+optical+radiation.">Neural stimulation with optical radiation.</a> Laser. Photonics Rev. 5 (1), 68-80 (2011).</li><li>Dittami, G. M., Rajguru, S. M., Lasher, R. A., Hitchcock, R. W., Rabbitt, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intracellular+calcium+transients+evoked+by+pulsed+infrared+radiation+in+neonatal+cardiomyocytes.">Intracellular calcium transients evoked by pulsed infrared radiation in neonatal cardiomyocytes.</a> J. Physiol. 589 (6), 1295-1306 (2011).</li><li>Thompson, A. C., Wade, S. A., Brown, W. G. A., Stoddart, P. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modeling+of+light+absorption+in+tissue+during+infrared+neural+stimulation.">Modeling of light absorption in tissue during infrared neural stimulation.</a> J. Biomed. Opt. 17 (7), 075002-075002 (2012).</li><li>Thompson, A. C., Wade, S. A., Cadusch, P. J., Brown, W. G., Stoddart, P. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modeling+of+the+temporal+effects+of+heating+during+infrared+neural+stimulation.">Modeling of the temporal effects of heating during infrared neural stimulation.</a> J. Biomed. Opt. 18 (3), 035004 (2013).</li><li>Huang, H., Delikanli, S., Zeng, H., Ferkey, D. M., Pralle, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Remote+control+of+ion+channels+and+neurons+through+magnetic-field+heating+of+nanoparticles.">Remote control of ion channels and neurons through magnetic-field heating of nanoparticles.</a> Nat. Nanotechnol. 5 (8), 602-606 (2010).</li><li>Farah, N., 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=Holographically+patterned+activation+using+photo-absorber+induced+neural-thermal+stimulation.">Holographically patterned activation using photo-absorber induced neural-thermal stimulation.</a> J. Neural. Eng. 10 (5), (2013).</li><li>Ciofani, G., 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=Enhancement+of+neurite+outgrowth+in+neuronal-like+cells+following+boron+nitride+nanotube-mediated+stimulation.">Enhancement of neurite outgrowth in neuronal-like cells following boron nitride nanotube-mediated stimulation.</a> ACS Nano. 4 (10), 6267-6277 (2010).</li><li>Kim, J. A., 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=Enhancement+of+neurite+outgrowth+in+PC12+cells+by+iron+oxide+nanoparticles.">Enhancement of neurite outgrowth in PC12 cells by iron oxide nanoparticles.</a> Biomaterials. 32 (11), 2871-2877 (2011).</li><li>Myroshnychenko, V., 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=Modelling+the+optical+response+of+gold+nanoparticles.">Modelling the optical response of gold nanoparticles.</a> Chem. Soc. Rev. 37 (9), 1792-1805 (2008).</li><li>Choi, W. I., Sahu, A., Kim, Y. H., Tae, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photothermal+cancer+therapy+and+imaging+based+on+gold+nanorods.">Photothermal cancer therapy and imaging based on gold nanorods.</a> Ann. Biomed. Eng. 40 (2), 534-546 (2011).</li><li>Zhan, Q., Qian, J., Li, X., He, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+study+of+mesoporous+silica-encapsulated+gold+nanorods+as+enhanced+light+scattering+probes+for+cancer+cell+imaging.">A study of mesoporous silica-encapsulated gold nanorods as enhanced light scattering probes for cancer cell imaging.</a> Nanotechnology. 21 (5), 055704 (2010).</li><li>Paviolo, C., 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=Laser+exposure+of+gold+nanorods+can+increase+neuronal+cell+outgrowth.">Laser exposure of gold nanorods can increase neuronal cell outgrowth.</a> Biotechnol. Bioeng. 110 (8), 2277-2291 (2013).</li><li>Paviolo, C., Haycock, J. W., Cadusch, P. J., McArthur, S. L., Stoddart, P. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Laser+exposure+of+gold+nanorods+can+induce+intracellular+calcium+transients.">Laser exposure of gold nanorods can induce intracellular calcium transients.</a> J. Biophotonics. 7 (10), 761-765 (2014).</li><li>Yong, J., 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=Gold-nanorod-assisted+near-infrared+stimulation+of+primary+auditory+neurons.">Gold-nanorod-assisted near-infrared stimulation of primary auditory neurons.</a> Adv. Healthcare Mater. , (2014).</li><li>Eom, K., 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=Enhanced+infrared+neural+stimulation+using+localized+surface+plasmon+resonance+of+gold+nanorods.">Enhanced infrared neural stimulation using localized surface plasmon resonance of gold nanorods.</a> Small. , (2014).</li><li>Juste, J., Pastoriza-Santos, I., Liz-Marz&#225;n, L. M., Mulvaney, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gold+nanorods:+Synthesis,+characterization+and+applications.">Gold nanorods: Synthesis, characterization and applications.</a> Coordination Chemistry Reviews. (17-18), 1870-1901 (2005).</li><li>Shang, J., Gao, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanoparticle+counting:+towards+accurate+determination+of+the+molar+concentration.">Nanoparticle counting: towards accurate determination of the molar concentration.</a> Chem. Soc. Rev. 43 (21), 7267-7278 (2014).</li><li>Sharma, V., Park, K., Srinivasarao, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Shape+separation+of+gold+nanorods+using+centrifugation.">Shape separation of gold nanorods using centrifugation.</a> Proc. Natl. Acad. Sci. 106 (13), 4981-4985 (2009).</li><li>Kaewkhaw, R., Scutt, A. M., Haycock, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anatomical+site+influences+the+differentiation+of+adipose-derived+stem+cells+for+schwann-cell+phenotype+and+function.">Anatomical site influences the differentiation of adipose-derived stem cells for schwann-cell phenotype and function.</a> Glia. 59 (5), 734-749 (2011).</li><li>Brown, W. G. A., Needham, K., Nayagam, B. A., Stoddart, P. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Whole+cell+patch+clamp+for+investigating+the+mechanisms+of+infrared+neural+stimulation.">Whole cell patch clamp for investigating the mechanisms of infrared neural stimulation.</a> JoVE. (77), (2013).</li><li>Cadusch, P. J., Hlaing, M. M., Wade, S. A., McArthur, S. L., Stoddart, P. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+methods+for+fluorescence+background+subtraction+from+Raman+spectra.">Improved methods for fluorescence background subtraction from Raman spectra.</a> J. Raman Spectrosc. 44 (11), 1587-1595 (2013).</li><li>Daud, M. F. B., Pawar, K. C., Claeyssens, F., Ryan, A. J., Haycock, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+aligned+3D+neuronal-glial+co-culture+model+for+peripheral+nerve+studies.">An aligned 3D neuronal-glial co-culture model for peripheral nerve studies.</a> Biomaterials. 33 (25), 5901-5913 (2012).</li><li>Jung, S., 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=Intracellular+gold+nanoparticles+increase+neuronal+excitability+and+aggravate+seizure+activity+in+the+mouse+brain.">Intracellular gold nanoparticles increase neuronal excitability and aggravate seizure activity in the mouse brain.</a> PLoS ONE. 9 (3), e91360 (2014).</li><li>Salinas, K., Kereselidze, Z., DeLuna, F., Peralta, X., Santamaria, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transient+extracellular+application+of+gold+nanostars+increases+hippocampal+neuronal+activity.">Transient extracellular application of gold nanostars increases hippocampal neuronal activity.</a> J. Nanobiotechnology. 12 (1), 31 (2014).</li><li>Ebbesen, C. L., Bruus, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+laser-induced+heating+in+optical+neuronal+guidance.">Analysis of laser-induced heating in optical neuronal guidance.</a> J. Neurosci. Meth. 209 (1), 168-177 (2012).</li><li>Iwanaga, S., 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=Location-dependent+photogeneration+of+calcium+waves+in+HeLa+cells.">Location-dependent photogeneration of calcium waves in HeLa cells.</a> Cell Biochem. Biophys. 45 (2), 167-176 (2006).</li><li>Huang, X., Jain, P. K., El-Sayed, I. H., El-Sayed, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+the+minimum+temperature+required+for+selective+photothermal+destruction+of+cancer+cells+with+the+use+of+immunotargeted+gold+nanoparticles.">Determination of the minimum temperature required for selective photothermal destruction of cancer cells with the use of immunotargeted gold nanoparticles.</a> Photochem. Photobiol. 82 (2), 412-417 (2006).</li><li>Connor, E. E., Mwamuka, J., Gole, A., Murphy, C. J., Wyatt, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gold+nanoparticles+are+taken+up+by+human+cells+but+do+not+cause+acute+cytotoxicity.">Gold nanoparticles are taken up by human cells but do not cause acute cytotoxicity.</a> Small. 1 (3), 325-327 (2005).</li><li>Isomaa, B., Reuter, J., Djupsund, B. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+subacute+and+chronic+toxicity+of+cetyltrimethylammonium+bromide+(CTAB),+a+cationic+surfactant,+in+the+rat.">The subacute and chronic toxicity of cetyltrimethylammonium bromide (CTAB), a cationic surfactant, in the rat.</a> Arch. Toxicol. 35 (2), 91-96 (1976).</li><li>Juste, J., Pastoriza-Santos, I., Liz-Marz&#225;n, L., Mulvaney, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gold+nanorods:+synthesis,+characterization+and+applications.">Gold nanorods: synthesis, characterization and applications.</a> Coord. Chem. Rev. 249 (17-18), 1870-1901 (2005).</li><li>Dreaden, E. C., Alkilany, A. M., Huang, X., Murphy, C. J., El-Sayed, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+golden+age:+gold+nanoparticles+for+biomedicine.">The golden age: gold nanoparticles for biomedicine.</a> Chem. Soc. Rev. 41 (7), 2740-2779 (2012).</li><li>Huang, X., Jain, P. K., El-Sayed, I. H., El-Sayed, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plasmonic+photothermal+therapy+(PPTT)+using+gold+nanoparticles.">Plasmonic photothermal therapy (PPTT) using gold nanoparticles.</a> Lasers Med. Sci. 23 (3), 217-228 (2008).</li><li>Albert, E. S., 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=TRPV4+channels+mediate+the+infrared+laser-evoked+response+in+sensory+neurons.">TRPV4 channels mediate the infrared laser-evoked response in sensory neurons.</a> J. Neurophysiol. 107 (12), 3227-3234 (2012).</li><li>Garcia-Elias, A., 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=Phosphatidylinositol-4,5-biphosphate-dependent+rearrangement+of+TRPV4+cytosolic+tails+enables+channel+activation+by+physiological+stimuli.">Phosphatidylinositol-4,5-biphosphate-dependent rearrangement of TRPV4 cytosolic tails enables channel activation by physiological stimuli.</a> Proceedings of the National Academy of Sciences of the United States of America. 110 (23), 9553-9558 (2013).</li><li>Shapiro, M. G., Homma, K., Villarreal, S., Richter, C. -. 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 vistas.  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.