Name: synthesis of poly(n-isopropylacrylamide) janus microhydrogels for anisotropic thermo-responsiveness and organophilic/hydrophilic loading capability
Uploaded: 2016-02-27T13:00:00
Description: Watch this Scientific Journal Video about Synthesis of PolyN-isopropylacrylamide Janus Microhydrogels for Anisotropic Thermo-responsiveness and Organophilic/Hydrophilic Loading Capability at JoVE.com

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea Government (MSIP (Nos. 2014R1A2A1A01006527 and 2011-0030075).

1. Fabrication of a Master Mold for the Hydrodynamic Focusing Microfluidic Device (HFMD) through Photolithography
<ol>
	<li>Design a photomask for the HFMD (Figure 1a) using computer-assisted design (CAD) software according to the manufacturer&#39;s protocol.</li>
	<li>Rinse a 4&#39; silicon wafer with acetone, isopropyl alcohol (IPA), and deionized (DI) water to remove organic and inorganic dust from the wafer.</li>
	<li>Clean the silicon wafer with O2 plasma at 100 W of power for 5 min to ...

<ol>
	<li>Hoffman, A. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrogels+for+biomedical+applications.">Hydrogels for biomedical applications.</a> Adv. Drug Delivery Rev. 54 (1), 3-12 (2002).</li><li>Qiu, Y., Park, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Environment-sensitive+hydrogels+for+drug+delivery.">Environment-sensitive hydrogels for drug delivery.</a> Adv. Drug Delivery Rev. 53 (3), 321-339 (2001).</li><li>Hirokawa, Y., Tanaka, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Volume+phase+transition+in+a+nonionic+gel.">Volume phase transition in a nonionic gel.</a> J. Chem. Phys. 81 (12), 6379-6380 (1984).</li><li>Bae, Y. H., Okano, T., Hsu, R., Kim, S. 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Photobiol. 85 (4), 848-860 (2009).</li><li>Tanaka, T., Nishio, I., Sun, S. T., Ueno-Nishio, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Collapse+of+gels+in+an+electric+field.">Collapse of gels in an electric field.</a> Science. 218 (4571), 467-469 (1982).</li><li>Kwon, I. C., Bae, Y. H., Kim, S. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrically+credible+polymer+gel+for+controlled+release+of+drugs.">Electrically credible polymer gel for controlled release of drugs.</a> Nature. 354 (6351), 291-293 (1991).</li><li>Obaidat, A. A., Park, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+protein+release+through+glucose-sensitive+hydrogel+membranes.">Characterization of protein release through glucose-sensitive hydrogel membranes.</a> Biomaterials. 18 (11), 801-806 (1997).</li><li>Kataoka, K., Miyazaki, H., Bunya, M., Okano, T., Sakurai, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Totally+synthetic+polymer+gels+responding+to+external+glucose+concentration:+their+preparation+and+application+to+on-off+regulation+of+insulin+release.">Totally synthetic polymer gels responding to external glucose concentration: their preparation and application to on-off regulation of insulin release.</a> J. Am. Chem. Soc. 120 (48), 12694-12695 (1998).</li><li>Heskins, M., Guillet, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Solution+properties+of+poly(N-isopropylacrylamide).">Solution properties of poly(N-isopropylacrylamide).</a> J. Macromol. Sci. Part A Pure Appl. Chem. 2 (8), 1441-1455 (1968).</li><li>Sasaki, S., Okabe, S., Miyahara, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermodynamic+properties+of+N-isopropylacrylamide+in+water:+solubility+transition,+phase+separation+of+supersaturated+solution,+and+glass+formation.">Thermodynamic properties of N-isopropylacrylamide in water: solubility transition, phase separation of supersaturated solution, and glass formation.</a> J. Phys. Chem. B. 114 (46), 14995-15002 (2010).</li><li>Bromberg, L., Alakhov, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+polyether-modified+poly(acrylic+acid)+microgels+on+doxorubicin+transport+in+human+intestinal+epithelial+Caco-2+cell+layers.">Effects of polyether-modified poly(acrylic acid) microgels on doxorubicin transport in human intestinal epithelial Caco-2 cell layers.</a> J. Controlled Release. 88 (1), 11-22 (2003).</li><li>Coughlan, D. C., Quilty, F. P., Corrigan, O. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+drug+physicochemical+properties+on+swelling/deswelling+kinetics+and+pulsatile+drug+release+from+thermoresponsive+poly(N-isopropylacrylamide)+hydrogels.">Effect of drug physicochemical properties on swelling/deswelling kinetics and pulsatile drug release from thermoresponsive poly(N-isopropylacrylamide) hydrogels.</a> J. Controll. Release. 98 (1), 97-114 (2004).</li><li>Bergbreiter, D. E., Case, B. L., Liu, Y. S., Caraway, 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=Poly(N-isopropylacrylamide)+soluble+polymer+supports+in+catalysis+and+synthesis.">Poly(N-isopropylacrylamide) soluble polymer supports in catalysis and synthesis.</a> Macromolecules. 31 (18), 6053-6062 (1998).</li><li>Lapeyre, V., Gosse, I., Chevreux, S., Ravaine, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Monodispersed+glucose-responsive+microgels+operating+at+physiological+salinity.">Monodispersed glucose-responsive microgels operating at physiological salinity.</a> Biomacromolecules. 7 (12), 3356-3363 (2006).</li><li>Hoare, T., Pelton, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Engineering+glucose+swelling+responses+in+poly(N-isopropylacrylamide)-based+microgels.">Engineering glucose swelling responses in poly(N-isopropylacrylamide)-based microgels.</a> Macromolecules. 40 (3), 670-678 (2007).</li><li>Xu, S., Zhang, J., Paquet, C., Lin, Y., Kumacheva, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=From+hybrid+microgels+to+photonic+crystals.">From hybrid microgels to photonic crystals.</a> Adv. Funct. Mater. 13 (6), 468-472 (2003).</li><li>Clarke, J., Vincent, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stability+of+non-aqueous+microgel+dispersions+in+the+presence+of+free+polymer.">Stability of non-aqueous microgel dispersions in the presence of free polymer.</a> J. Chem. Soc., Faraday Trans. 1. 77 (8), 1831-1843 (1981).</li><li>Mears, S. J., Deng, Y., Cosgrove, T., Pelton, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structure+of+sodium+dodecyl+sulfate+bound+to+a+poly+(NIPAM)+microgel+particle.">Structure of sodium dodecyl sulfate bound to a poly (NIPAM) microgel particle.</a> Langmuir. 13 (7), 1901-1906 (1997).</li><li>Shah, R. K., Kim, J. W., Agresti, J. J., Weitz, D. A., Chu, L. 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G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polyvinyl+alcohol+particle+size+and+suspension+characteristics.">Polyvinyl alcohol particle size and suspension characteristics.</a> Am. J. Neuroradiol. 16 (6), 1335-1343 (1995).</li><li>Han, 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=Effect+of+flow+rates+on+generation+of+monodisperse+clay-poly(N-isopropylacrylamide)+embolic+microspheres+using+hydrodynamic+focusing+microfluidic+device.">Effect of flow rates on generation of monodisperse clay-poly(N-isopropylacrylamide) embolic microspheres using hydrodynamic focusing microfluidic device.</a> Jpn. J. Appl. Phys. 50 (6), 06-12 (2011).</li><li>Seo, K. D., Doh, J., Kim, D. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=One-step+microfluidic+synthesis+of+Janus+microhydrogels+with+anisotropic+thermo-responsive+behavior+and+organophilic/hydrophilic+loading+capability.">One-step microfluidic synthesis of Janus microhydrogels with anisotropic thermo-responsive behavior and organophilic/hydrophilic loading capability.</a> Langmuir. 29 (49), 15137-15141 (2013).</li><li>Seo, K. D., Kim, D. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfluidic+synthesis+of+thermo-responsive+poly(N-isopropylacrylamide)-poly(ethylene+glycol)+diacrylate+microhydrogels+as+chemo-embolic+microspheres.">Microfluidic synthesis of thermo-responsive poly(N-isopropylacrylamide)-poly(ethylene glycol) diacrylate microhydrogels as chemo-embolic microspheres.</a> J. Micromech. Microeng. 24 (8), 085001 (2014).</li><li>Seo, K. D., Kwak, B. K., Kim, D. S., S&#225;nchez, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfluidic-assisted+fabrication+of+flexible+and+location+traceable+organo-motor.">Microfluidic-assisted fabrication of flexible and location traceable organo-motor.</a> IEEE Trans. Nanobiosci. 14 (3), 298-304 (2015).</li><li>Seo, K. D., Kim, D. S., S&#225;nchez, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fabrication+and+application+of+complex-shaped+microparticles+via+microfluidics.">Fabrication and application of complex-shaped microparticles via microfluidics.</a> Lab Chip. , (2015).</li><li>Shah, R. K., Kim, J. W., Weitz, D. 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Commun. 47 (9), 2634-2636 (2011).</li><li>Hauber, K., Drier, T., Beebe, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PDMS+bonding+by+means+of+a+portable,+low-cost+corona+system.">PDMS bonding by means of a portable, low-cost corona system.</a> Lab chip. 6 (12), 1548-1549 (2006).</li><li>Nisisako, T., Torii, T., Takahashi, T., Takizawa, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+of+monodisperse+bicolored+Janus+particles+with+electrical+anisotropy+using+a+microfluidic+co-flow+system.">Synthesis of monodisperse bicolored Janus particles with electrical anisotropy using a microfluidic co-flow system.</a> Adv. Mater. 18 (9), 1152-1156 (2006).</li><li>Seiffert, S., Romanowsky, M. B., Weitz, D. 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Two immiscible base materials are generally used to synthesize the Janus microhydrogels. Until recently, Janus microhydrogels consisting of the same base material were rarely reported and the reported Janus microhydrogels did not have a clear internal morphology due to the disturbance caused by the miscibility of the component materials.35, 36 In this protocol, we demonstrate a method to synthesize Janus microhydrogels composed entirely of the single base material, PNIPAAm, with a clearly compartmentalized str...

Hydrogels are a network of hydrophilic polymer chains.1 An increasing amount of research in the field of hydrogels has promoted significant advances and revealed their similarity to biological tissues; the properties of hydrogels allow the uptake of large amounts of water while maintaining their structure. Environmentally responsive hydrogels have also been studied extensively because of their ability to swell or shrink reversibly in response to external stimuli.2 Several triggers, including temperature,3-5 pH,6,7 light,8,9 electric fields,10,11 and specific molecules, such as glucose,12,13 have been suggested to control the geometric shape of hydrogels. Among the many environmentally responsive hydrogels currently available, poly(N-isopropylacrylamide) (PNIPAAm), a well-known thermo-responsive hydrogel, exhibits volume shrinkage above a low critical solution temperature (LCST) of 32 &#176;C.14 A recent study by Sasaki et al.15 reported the intriguing liquid-liquid phase separation of supersaturated NIPAAm, which is the monomer of PNIPAAm. According to this report, supersaturated NIPAAm was dissolved with a 10-fold molar excess of H2O, and soon after, the solution separated into two liquid phases when allows to stand at a temperature above 25 &#176;C; by contrast, dilute NIPAAm was dissolved homogeneously under the same conditions.
Microparticles made of environmentally responsive hydrogels are fascinating candidates for application in drug delivery,16,17 catalysis,18 sensing,19,20 and photonics.21 Traditional synthetic methods including emulsion polymerization, are used to produce hydrogel microparticles with polydispersity.22,23 However, certain applications require microparticles with a narrow size distribution, for example, to stabilize the pharmacokinetics of drug delivery.24 Irregularly shaped or polydisperse embolic microparticles aggregate proximally into clusters, leading to chronic inflammatory responses in embolic particles for cancer therapeutic treatment.25,26
The microfluidic approach is at the forefront of research as a means of fabricating micro-sized particles with narrow size distributions and complex shapes.27-31 The advantages of fabricating microparticles in the microfluidic device are predicated by the small characteristic length of the microfluidic device, which results in a low Reynolds number. In contrast to traditional bulk emulsification where drops are formed in parallel, microdroplets produced in microfluidic devices are generated in series and subsequently polymerized into microparticles upon exposure to UV irradiation. The fundamental principle of droplet formation using a microfluidic device is balance between the interfacial tension and the shear force of the sheath fluid acting on the core fluid. 
Despite the obvious advantages of microfluidic fabrication of droplets/particles, Janus droplets/particles consisting of the same base material are rarely reported because the internal morphology of these droplets/particles is generally disturbed by the diffusion and perturbation of the core fluids. To circumvent this intrinsic limitation, two groups recently reported the preparation of the Janus microparticles by employing heat-induced phase separation of colloidal nanoparticles and UV-directed phase separation.32,33
To this end, we report a microfluidic approach to synthesize Janus microhydrogels entirely composed of a single base material and obtain a product with clearly compartmentalized morphology. Our approach is based on the primary concept of liquid-liquid phase separation of supersaturated NIPAAm monomer. The resulting Janus microhydrogels were found to possess unique properties including anisotropic thermo-responsiveness and organophilic/hydrophilic loading capability.

<table border="0" cellpadding="0" cellspacing="0" width="590">
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Silicon wafer</td>
			<td style="width:88px;">LG Siltron</td>
			<td style="width:119px;">4&#34;, Test grade</td>
			<td style="width:167px;">Wafer for master mold fabrication</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:216px;">Acetone</td>
			<td style="width:88px;">Samchun Pure Chemical</td>
			<td style="width:119px;">A0097</td>
			<td>Cleaning silicon wafer</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:216px;">Isopropyl alcohol (IPA)</td>
			<td style="width:88px;">Daejung Chemicals &#38; Metals</td>
			<td style="width:119px;">5035-4404</td>
			<td>Cleaning silicon wafer</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:216px;">Water purification system</td>
			<td style="width:88px;">Merck Millipore</td>
			<td style="width:119px;">EMD Millipore RIOs Essential 5</td>
			<td>Prepering&#160; deionized water</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">O2 plasma machine</td>
			<td style="width:88px;">Femto Science</td>
			<td style="width:119px;">VITA-A</td>
			<td>Cleaning silicon wafer</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">SU-8 2150 negative photoresist</td>
			<td style="width:88px;">MicroChem</td>
			<td style="width:119px;">Y111077 0500L1GL</td>
			<td>Photoresist for master mold fabrication</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Hot plate</td>
			<td style="width:88px;">Misung Scientific</td>
			<td style="width:119px;">HP330D, HP150D</td>
			<td>Baking SU-8</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">SU-8 developer</td>
			<td style="width:88px;">Microchem</td>
			<td style="width:119px;">Y020100 4000L1PE</td>
			<td>Developing SU-8</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Mask aligner system for photolithograpy</td>
			<td style="width:88px;">Shinu Mst Co.</td>
			<td style="width:119px;">CA-6M</td>
			<td>Photolithography</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Sylgard 184 silicone elastomer kit</td>
			<td style="width:88px;">Dow Corning</td>
			<td style="width:119px;">1064891</td>
			<td>PDMS casting</td>
		</tr>
		<tr height="80">
			<td height="80" style="height:80px;width:216px;">Laboratory Corona Treater</td>
			<td style="width:88px;">Electro-technic Products Inc.</td>
			<td style="width:119px;">Model BD-20AC</td>
			<td>PDMS air plasma treatment&#160;</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">N-isopropylacrylamide (NIPAAm)</td>
			<td style="width:88px;">Sigma-Aldrich</td>
			<td style="width:119px;">415324-50G</td>
			<td>Monomer</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:216px;">N,N&#39;-methylenebisacrylamide (MBAAm)</td>
			<td style="width:88px;">Sigma-Aldrich</td>
			<td style="width:119px;">146072-100G</td>
			<td>Crosslinker of NIPAAm</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:216px;">4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, Irgacure 2959</td>
			<td style="width:88px;">BASF</td>
			<td style="width:119px;">55047962</td>
			<td>Photoinitiator of NIPAAm</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">ABIL EM 90</td>
			<td style="width:88px;">Evonik Industries</td>
			<td style="width:119px;">201109</td>
			<td>Sufactant for oil</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:216px;">Vortex mixer</td>
			<td style="width:88px;">Scientific Industries Inc.</td>
			<td style="width:119px;">Vortex-Genie 2</td>
			<td>Mixing</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:216px;">Tygon tubing</td>
			<td style="width:88px;">Saint-Gobain</td>
			<td style="width:119px;">I.D. 1/32&#34;, O.D. 3/32&#34;, Wall 1/32&#34;</td>
			<td>Connecting tube between syringes and HFMD</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">UV light source</td>
			<td style="width:88px;">Hamamatsu</td>
			<td style="width:119px;">Spot light source LC8</td>
			<td>Polymerization from NIPAAm to PNIPAAm</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:216px;">Syringes, NORM-JECT (3ml)</td>
			<td style="width:88px;">Henke-Sass Wolf GmbH</td>
			<td style="width:119px;">22767</td>
			<td>Loading of materials</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Syringe pump</td>
			<td style="width:88px;">KD Scientific</td>
			<td style="width:119px;">KDS model 200</td>
			<td>Perfusion of materials</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Tegitol Type NP-10</td>
			<td style="width:88px;">Sigma-Aldrich</td>
			<td style="width:119px;">NP10-500ML</td>
			<td>Surfactant for water</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Oil red O</td>
			<td style="width:88px;">Sigma-Aldrich</td>
			<td style="width:119px;">O0625-25G</td>
			<td>Dye for N-rich phase</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Oil Blue N</td>
			<td style="width:88px;">Sigma-Aldrich</td>
			<td style="width:119px;">391557-5G</td>
			<td>Dye for N-rich phase</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Yellow food dye</td>
			<td style="width:88px;">Edentown F&#38;B</td>
			<td style="width:119px;">NA</td>
			<td>Dye for N-poor phase</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Green food dye</td>
			<td style="width:88px;">Edentown F&#38;B</td>
			<td style="width:119px;">NA</td>
			<td>Dye for N-poor phase</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Power supply</td>
			<td style="width:88px;">Agilent</td>
			<td style="width:119px;">E3649A</td>
			<td>Power soruce for thermoelectric moduel</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Thermoelectric module</td>
			<td style="width:88px;">Peltier</td>
			<td style="width:119px;">FALC1-12710T125</td>
			<td>Temparature control</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Centrifuge machine</td>
			<td style="width:88px;">Labogene</td>
			<td style="width:119px;">1248R</td>
			<td>Settling down microhydrogels</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">24-well plate</td>
			<td style="width:88px;">SPL Life Sciences</td>
			<td style="width:119px;">32024</td>
			<td>Reservoir for observation</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Optical microscope</td>
			<td style="width:88px;">Nikon</td>
			<td style="width:119px;">ECLIPSE 80i</td>
			<td>Optical observation</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Image analysis software</td>
			<td style="width:88px;">IMT i-Solution Inc.</td>
			<td style="width:119px;">iSolutions DT</td>
			<td>Measurement of radius</td>
		</tr>
	</tbody>
</table>

synthesis of poly(n-isopropylacrylamide) janus microhydrogels for anisotropic thermo-responsiveness and organophilic/hydrophilic loading capability

Janus microparticles are compartmentalized particles with differing molecular structures and/or functionality on each of their two sides. Because of this unique property, Janus microparticles have been recognized as a new class of materials, thereby attracting a great deal of attention from various research fields. The versatility of these microparticles has been exemplified through their uses as building blocks for self-assembly, electrically responsive actuators, emulsifiers for painting and cosmetics, and carriers for drug delivery. This study introduces a detailed protocol that explicitly describes a synthetic method for designing novel Janus microhydrogels composed of a single base material, poly(N-isopropylacrylamide) (PNIPAAm). Janus microdroplets are firstly generated via a hydrodynamic focusing microfluidic device (HFMD) based on the separation of a supersaturated aqueous NIPAAm monomer solution and subsequently polymerized through exposure to UV irradiation. The resulting Janus microhydrogels were found to be entirely composed of the same base material, featured an easily identifiable compartmentalized morphology, and exhibited anisotropic thermo-responsiveness and organophilic/hydrophilic loading capability. We believe that the proposed method introduces a novel hydrogel platform with the potential for advanced synthesis of multi-functional Janus microhydrogels.

Figure 3a presents a schematic of the experimental setup used to synthesize Janus microhydrogels via the HFMD. The N-rich and N-poor phases were precisely injected into the HFMD as core fluids 1 and 2 and then merged and broken up into Janus microdroplets at the orifice by the sheath fluid of mineral oil because of the Rayleigh capillary instability. Consequently, Janus microdroplets composed of N-rich and N-poor phases were successfully generated as shown in <st...

Watch this Scientific Journal Video about Synthesis of PolyN-isopropylacrylamide Janus Microhydrogels for Anisotropic Thermo-responsiveness and Organophilic/Hydrophilic Loading Capability at JoVE.com

Synthesis of PolyN-isopropylacrylamide Janus Microhydrogels for Anisotropic Thermo-responsiveness and Organophilic/Hydrophilic Loading Capability

We present a protocol to synthesize Janus microhydrogels composed entirely of the same base material, poly(N-isopropylacrylamide) (PNIPAAm), with a clearly compartmentalized structure base on the phase separation of a supersaturated NIPAAm monomer solution. The synthesized Janus microhydrogels show unique properties such as anisotropic thermo-responsiveness and organophilic/hydrophilic loading capability.

Synthesis of Poly(N-isopropylacrylamide) Janus Microhydrogels for Anisotropic Thermo-responsiveness and Organophilic/Hydrophilic Loading Capability

Janus microparticles are compartmentalized particles with differing molecular structures and/or functionality on each of their two sides. Because of this ...

The overall goal of this experiment is to synthesize janus microhydrogels that are composed of the same base material and have an isotropic thermo-responsiveness, as well as organophilic and hydrophilic loading capability using the liquid-liquid phase separation of super-saturated N-isopropylacrylamide monomer. Masote can help answer key questions in the field of drop delivery systems, specifically for the development of advanced trocharia, which requires hydrophilic/organophilic fuel holding capability inside a single particle. The main advantage of this patho is to synthesize mono dispered janus microhydrogels with the clearly compartmentalized intomorphology and to modulate the size of the janus microhydrogels with the help of microphilic device.Demonstrating the procedure will be done by Kyoung Duck Seo and Andrew Choi who are my PhD students. Use the patterned wafer obtained as described in the text protocol as the master mold for PDMS casting. Mix the PDMS prepolymer and a curing agent homogeneously at a weight ratio of 10 to one.For example, use one gram of curing agent for 10 grams of PDMS prepolymer. Pour the PDMS prepolymer into the master mold and degas it for one hour in a vacuum chamber. Then, place the master mold with the PDMS prepolymer into an oven at 65 degrees Celsius for three hours.Cut the cured PDMS into the size of a single chip using a sharp scalpel. Carefully peel off the cured PDMS replica from the master mold by hand. Punch inlet and outlet holes into one of the replicas using a hole puncher with a slightly smaller diameter than the outer diameter of the connecting tubing.Then, apply air plasma treatment to the bonding area of each replica using a Corona treater. Drop five microliters of methanol onto the air plasma treated areas. Finally align two identical PDMS replicas to fabricate the HFMD by hand manipulation.And check alignment via a microscope. Place the HFMD in an oven set to 65 degrees Celsius overnight to strengthen the bond between the two PDMS replicas. Dissolve NIPAAm monomer in de-ionized water at a weight to weight ratio of one to one using a vortex mixer.For example, dissolve 10 grams of NIPAAm in 10 milliliters of de-ionized water. Allow the monomer solution to rest in a vertical position at room temperature for at least 15 minutes. When the interface separating the two phases becomes clear, carefully extract two milliliters of monomer solution from the N-rich and N-poor phases without disturbing this interface by using a pipette.Next, add four milligrams of MBAAm to the extracted N-rich and N-poor monomer solutions as a crosslinker. Then, add four milligrams of the photoinitiator to the solutions to prepare core fluids one and two for the low crosslinker concentration sample. Finally, dissolve 10 weight percentage of oil surfactant into mineral oil to prepare the sheath fluid.Load two milliliters of core fluids one and two and the sheath fluid into three separate three millileter syringes. Mount the syringes into the syringe pumps and connect each syringe to the appropriate fluid inlet of the HFMD using tubing. Use the tubing to connect the fluid outlet of the HFMD to a collection reservoir.Set the syringe pumps to infuse core fluids one and two at flow rates of two microliters per minute. And to infuse the sheath fluid at 10 microliters per minute. Then, position the UV light source perpendicularly about one centimeter away from the collection reservoir.Switch on the UV light source and visually monitor the continuous production of janus microhydrogels. Collect the fabricated janus microhydrogels into a conical tube and wash them using isopropyl alcohol. Then, centrifuge the conical tube to settle the microhydrogels.Repeat the centrifugation step using de-ionized water with the water surfactant to remove the leftover isopropyl alcohol around the janus microhydrogels. Store completely washed janus microhydrogels in a 10 milliliter vial containing de-ionized water. Use a pipette to place the synthesized janus microhydrogels into a 24 well plate.Allow the hydrogels to settle for 15 seconds until a mono layer is formed at the bottom surface of the well. Obtain an image of the janus microhydrogel at 24 degrees Celsius using an upright optical microscope with a 5x objective lens. Set a thermoelectric module under the well plate and control the voltage of this module to increase the temperature of the solution containing janus microhydrogels to 32 degrees Celsius.Obtain an image of the janus microhydrogel at 32 degrees Celsius once more by using an upright optical microscope with a 5x objective lens. From the 25 images of different janus microhydrogels at 24 and 32 degrees Celsius, measure the radius of the polymerized phases pN-rich and pN-poor using image analysis software according to the manufacturer's instructions. Shown here is the schematic diagram of the HFMD for generating janus microdroplets.The N-rich and N-poor solutions are precisely injected into the HFMD and broken up into microdroplets at the orifice by the sheath fluid of mineral oil. Janus microdroplets obtained through HFMD have different volume ratios of N-rich and N-poor solutions as shown here. The volume ratio of the N-rich and N-poor solution composing microhydrogels is controlled by altering the flow rate of each solution.Here, schematic diagrams and optical micrographs of the janus microdroplets and microhydrogels in response to environmental and temperature changes are shown. To quantify thermo-responsiveness, the radius of the janus microdroplets and microhydrogels was measured and showed in anisotropic, thermo-responsive behavior which is caused by the differences in NIPAAm monomer concentration between pN-rich and pN-poor. The organophilic/hydrophilic loading capability of these microhydrogels is observed as fat-soluble dyes strongly prefer to dissolve in the N-rich solution.While water soluble dyes prefer to dissolve in the N-poor solution. Janus microhydrogels with hydrophilic/organophilic dual loading capability inside a single particle are finally fabricated. Once mastered, this technique can be done in 40 minutes if it is prepared properly.While attempting this procedure, it is important to remember to maintain the ambient condition, especially the temperature, because highly concentrated NIPAAm solution crystallizes below 25 degrees Celsius. After its development, this technique will pave the way for researchers in the field of drug delivery systems to develop functional microhydrogels that can control the drug releasing rates and encapsulate multi-drugs without cross-contamination. After watching this video you should have a good understanding of how to synthesize janus microhydrogels composed of base material poly NIPAAm.

synthesis-polyn-isopropylacrylamide-janus-microhydrogels-for

Research

JoVE Journal

Chemistry

Synthesis, Cellular Delivery and In vivo Application of Dendrimer-based pH Sensors

The development of fluorescent indicators represented a revolution for life sciences. Genetically encoded and synthetic fluorophores with sensing abilities allowed the visualization of biologically relevant species with high spatial and temporal resolution. Synthetic dyes are of particular interest thanks to their high tunability and the wide range of measureable analytes. However, these molecules suffer several limitations related to small molecule behavior (poor solubility, difficulties in targeting, often no ratiometric imaging allowed). In this work we introduce the development of dendrimer-based sensors and present a procedure for pH measurement in vitro, in living cells and in vivo. We choose dendrimers as ideal platform for our sensors for their many desirable properties (monodispersity, tunable properties, multivalency) that made them a widely used scaffold for several biomedical devices. The conjugation of fluorescent pH indicators to the dendrimer scaffold led to an enhancement of their sensing performances. In particular dendrimers exhibit reduced cell leakage, improved intracellular targeting and allow ratiometric measurements. These novel sensors were successfully employed to measure pH in living HeLa cells and in vivo in mouse brain.

Synthesis, Cellular Delivery and In vivo Application of Dendrimer-based pH Sensors

Fluorescence sensors are powerful tools in life science. Here we describe a methodology to synthesize and use dendrimer-based fluorescent sensors to measure pH in living cells and in vivo. The dendritic scaffold enhances the properties of conjugated fluorescent dyes leading to improved sensing properties.

The development of  fluorescent indicators represented a revolution for life sciences. Genetically  encoded and synthetic fluorophores with sensing ...

Seeded Synthesis of CdSe/CdS Rod and Tetrapod Nanocrystals

We demonstrate a method for the synthesis of multicomponent nanostructures consisting of CdS and CdSe with rod and tetrapod morphologies. A seeded synthesis strategy is used in which spherical seeds of CdSe are prepared first using a hot-injection technique. By controlling the crystal structure of the seed to be either wurtzite or zinc-blende, the subsequent hot-injection growth of CdS off of the seed results in either a rod-shaped or tetrapod-shaped nanocrystal, respectively. The phase and morphology of the synthesized nanocrystals are confirmed using X-ray diffraction and transmission electron microscopy, demonstrating that the nanocrystals are phase-pure and have a consistent morphology. The extinction coefficient and quantum yield of the synthesized nanocrystals are calculated using UV-Vis absorption spectroscopy and photoluminescence spectroscopy. The rods and tetrapods exhibit extinction coefficients and quantum yields that are higher than that of the bare seeds. This synthesis demonstrates the precise arrangement of materials that can be achieved at the nanoscale by using a seeded synthetic approach.

A protocol for the seeded synthesis of rod-shaped and tetrapod-shaped multicomponent nanostructures consisting of CdS and CdSe is presented.

We demonstrate a method for the synthesis of multicomponent nanostructures consisting of CdS and CdSe with rod and tetrapod morphologies. A seeded ...

Synthesis and Characterization of Supramolecular Colloids

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical properties for applications in photonics, drug delivery and coating technology. Here we present a new family of colloidal building blocks, coined supramolecular colloids, whose self-assembly is controlled through surface-functionalization with a benzene-1,3,5-tricarboxamide (BTA) derived supramolecular moiety. Such BTAs interact via directional, strong, yet reversible hydrogen-bonds with other identical BTAs. Herein, a protocol is presented that describes how to couple these BTAs to colloids and how to quantify the number of coupling sites, which determines the multivalency of the supramolecular colloids. Light scattering measurements show that the refractive index of the colloids is almost matched with that of the solvent, which strongly reduces the van der Waals forces between the colloids. Before photo-activation, the colloids remain well dispersed, as the BTAs are equipped with a photo-labile group that blocks the formation of hydrogen-bonds. Controlled deprotection with UV-light activates the short-range hydrogen-bonds between the BTAs, which triggers the colloidal self-assembly. The evolution from the dispersed state to the clustered state is monitored by confocal microscopy. These results are further quantified by image analysis with simple routines using ImageJ and Matlab. This merger of supramolecular chemistry and colloidal science offers a direct route towards light- and thermo-responsive colloidal assembly encoded in the surface-grafted monolayer.

A protocol for the synthesis and characterization of colloids coated with supramolecular moieties is described. These supramolecular colloids undergo self-assembly upon the activation of the hydrogen-bonds between the surface-anchored molecules by UV-light.

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical ...

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the development of antibody drug conjugates (ADCs) and nanomedicine, fluorescent microscopy and systems chemistry. For many of these applications, specificity of the bioconjugation method used is of prime concern. The Michael addition of maleimides with cysteine(s) on the target proteins is highly selective and proceeds rapidly under mild conditions, making it one of the most popular methods for protein bioconjugation.
We demonstrate here the modification of the only surface-accessible cysteine residue on yeast cytochrome c with a ruthenium(II) bisterpyridine maleimide. The protein bioconjugation is verified by gel electrophoresis and purified by aqueous-based fast protein liquid chromatography in 27% yield of isolated protein material. Structural characterization with MALDI-TOF MS and UV-Vis is then used to verify that the bioconjugation is successful. The protocol shown here is easily applicable to other cysteine - maleimide coupling of proteins to other proteins, dyes, drugs or polymers.

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

This protocol details the important steps required for the bioconjugation of a cysteine containing protein to a maleimide, including reagent purification, reaction conditions, bioconjugate purification and bioconjugate characterization.

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the ...

Hydroquinone Based Synthesis of Gold Nanorods

Gold nanorods are an important kind of nanoparticles characterized by peculiar plasmonic properties. Despite their widespread use in nanotechnology, the synthetic methods for the preparation of gold nanorods are still not fully optimized. In this paper we describe a new, highly efficient, two-step protocol based on the use of hydroquinone as a mild reducing agent. Our approach allows the preparation of nanorods with a good control of size and aspect ratio (AR) simply by varying the amount of hexadecyl trimethylammonium bromide (CTAB) and silver ions (Ag+) present in the "growth solution". By using this method, it is possible to markedly reduce the amount of CTAB, an expensive and cytotoxic reagent, necessary to obtain the elongated shape. Gold nanorods with an aspect ratio of about 3 can be obtained in the presence of just 50 mM of CTAB (versus 100 mM used in the standard protocol based on the use of ascorbic acid), while shorter gold nanorods are obtained using a concentration as low as 10 mM.

This paper describes a protocol for the synthesis of gold nanorods, based on the use of hydroquinone as reducing agent, plus the different mechanisms for controlling their size and aspect ratio.

Gold nanorods are an important kind of nanoparticles characterized by peculiar plasmonic properties. Despite their widespread use in nanotechnology, the ...

Controlled Synthesis and Fluorescence Tracking of Highly Uniform Poly(N-isopropylacrylamide) Microgels

Stimuli-sensitive poly(N-isopropylacrylamide) (PNIPAM) microgels have various prospective practical applications and uses in fundamental research. In this work, we use single particle tracking of fluorescently labeled PNIPAM microgels as a showcase for tuning microgel size by a rapid non-stirred precipitation polymerization procedure. This approach is well suited for prototyping new reaction compositions and conditions or for applications that do not require large amounts of product. Microgel synthesis, particle size and structure determination by dynamic and static light scattering are detailed in the protocol. It is shown that the addition of functional comonomers can have a large influence on the particle nucleation and structure. Single particle tracking by wide-field fluorescence microscopy allows for an investigation of the diffusion of labeled tracer microgels in a concentrated matrix of non-labeled microgels, a system not easily investigated by other methods such as dynamic light scattering.

Controlled Synthesis and Fluorescence Tracking of Highly Uniform PolyN-isopropylacrylamide Microgels

Non-stirred precipitation polymerization provides a rapid, reproducible prototyping approach to the synthesis of stimuli-sensitive poly(N-isopropylacrylamide) microgels of narrow size distribution. In this protocol synthesis, light scattering characterization and single particle fluorescence tracking of these microgels in a wide-field microscopy setup are demonstrated.

Stimuli-sensitive poly(N-isopropylacrylamide) (PNIPAM) microgels have various prospective practical applications and uses in fundamental research. In this ...

Facet-to-facet Linking of Shape-anisotropic Colloidal Cadmium Chalcogenide Nanostructures

Here, we describe a protocol that allows for shape-anisotropic cadmium chalcogenide nanocrystals (NCs), such as nanorods (NRs) and tetrapods (TPs), to be covalently and site-specifically linked via their end facets, resulting in polymer-like linear or branched chains. The linking procedure begins with a cation-exchange process in which the end facets of the cadmium chalcogenide NCs are first converted to silver chalcogenide. This is followed by the selective removal of ligands at their surface. This results in cadmium chalcogenide NCs with highly reactive silver chalcogenide end facets that spontaneously fuse upon contact with each other, thereby establishing an interparticle facet-to-facet attachment. Through the judicious choice of precursor concentrations, an extensive network of linked NCs can be produced. Structural characterization of the linked NCs is carried out via low- and high-resolution transmission electron microscopy (TEM), as well as energy-dispersive X-ray spectroscopy, which confirm the presence of silver chalcogenide domains between chains of cadmium chalcogenide NCs.

A protocol detailing how shape-anisotropic colloidal cadmium chalcogenide nanocrystals can be covalently linked via their end facets is presented here.

Here, we describe a protocol that allows for shape-anisotropic cadmium chalcogenide nanocrystals (NCs), such as nanorods (NRs) and tetrapods (TPs), to be ...

Grafting Multiwalled Carbon Nanotubes with Polystyrene to Enable Self-Assembly and Anisotropic Patchiness

We demonstrate a straightforward protocol to graft pristine multiwalled carbon nanotubes (MWCNTs) with polystyrene (PS) chains at the sidewalls through a free-radical polymerization strategy to enable the modulation of the nanotube surface properties and produce supramolecular self-assembly of the nanostructures. First, a selective hydroxylation of the pristine nanotubes through a biphasic catalytically mediated oxidation reaction creates superficially distributed reactive sites at the sidewalls. The latter reactive sites are subsequently modified with methacrylic moieties using a silylated methacrylic precursor to create polymerizable sites. Those polymerizable groups can address further polymerization of styrene to produce a hybrid nanomaterial containing PS chains grafted to the nanotube sidewalls. The polymer-graft content, amount of silylated methacrylic moieties introduced and hydroxylation modification of the nanotubes are identified and quantified by Thermogravimetric Analysis (TGA). The presence of reactive functional groups hydroxyl and silylated methacrylate are confirmed by Fourier Transform Infrared Spectroscopy (FT-IR). Polystyrene-grafted carbon nanotube solutions in tetrahydrofuran (THF) provide wall-to-wall collinearly self-assembled nanotubes when cast samples are analyzed by transmission electron microscopy (TEM). Those self-assemblies are not obtained when suitable blanks are similarly cast from analogous solutions containing non-grafted counterparts. Therefore, this method enables the modification of the nanotube anisotropic patchiness at the sidewalls which results into spontaneous auto-organization at the nanoscale.

A procedure for the synthesis of polystyrene-grafted multiwalled carbon nanotubes using successive chemical modification steps to selectively introduce the polymer chains to the sidewalls and their self-assembly via anisotropic patchiness is presented.

We demonstrate a straightforward protocol to graft pristine multiwalled carbon nanotubes (MWCNTs) with polystyrene (PS) chains at the sidewalls through a ...

Preparation of Hollow Polystyrene Particles and Microcapsules by Radical Polymerization of Janus Droplets Consisting of Hydrocarbon and Fluorocarbon Oils

In this article, we have demonstrated a method for producing hollow particles and microcapsules using oil droplets consisting of hydrocarbon oil (styrene) and fluorocarbon oil (perfluoro-n-octane, PFO) in aqueous surfactant (sodium dodecylsulfate, SDS) solutions. Since fluorocarbon oils are immiscible with hydrocarbon oils, the two oils are separated. Emulsions are prepared by stirring styrene/PFO/aqueous SDS solution mixtures at 80 &#176;C. The type of emulsions and the morphology of droplets in the emulsions are observed by light microscope and scanning confocal fluorescence microscope. It is found that oil droplets with Janus-type morphologies consisting of mutually immiscible styrene and PFO are formed in aqueous SDS solutions. Polystyrene particles are fabricated by radical polymerization of the ternary mixtures of styrene/PFO/aqueous SDS solution at 80 &#176;C. The morphologies of the polystyrene are confirmed by scanning electron microscopy and scanning transmission electron microscopy observations. These observations show the preparation of hollow polystyrene particles with a single hole on the surface. To our knowledge, this method is a novel strategy using the immiscibility of hydrocarbon and fluorocarbon oils. The hollow particles can also be applied to the preparation of microcapsules.

A protocol for the fabrication of hollow polymer particles and microcapsules by radical polymerization using emulsions consisting of styrene, perfluoro-n-octane, and aqueous SDS (sodium dodecylsulfate) solution is presented.

In this article, we have demonstrated a method for producing hollow particles and microcapsules using oil droplets consisting of hydrocarbon oil (styrene) ...

Synthesis of Substrate-Bound Au Nanowires Via an Active Surface Growth Mechanism

Advancing synthetic capabilities is important for the development of nanoscience and nanotechnology. The synthesis of nanowires has always been a challenge, as it requires asymmetric growth of symmetric crystals. Here, we report a distinctive synthesis of substrate-bound Au nanowires. This template-free synthesis employs thiolated ligands and substrate adsorption to achieve the continuous asymmetric deposition of Au in solution at ambient conditions. The thiolated ligand prevented the Au deposition on the exposed surface of the seeds, so the Au deposition only occurs at the interface between the Au seeds and the substrate. The side of the newly deposited Au nanowires is immediately covered with the thiolated ligand, while the bottom facing the substrate remains ligand-free and active for the next round of Au deposition. We further demonstrate that this Au nanowire growth can be induced on various substrates, and different thiolated ligands can be used to regulate the surface chemistry of the nanowires. The diameter of the nanowires can also be controlled with mixed ligands, in which another &#34;bad&#34; ligand could turn on the lateral growth. With the understanding of the mechanism, Au nanowire-based nanostructures can be designed and synthesized.

We report a solution-based method to synthesize substrate-bound Au nanowires. By tuning the molecular ligands used during the synthesis, the Au nanowires can be grown from various substrates with different surface properties. Au nanowire-based nanostructures can also be synthesized by adjusting the reaction parameters.