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. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermo-sensitive+polymers+as+on-off+switches+for+drug+release.">Thermo-sensitive polymers as on-off switches for drug release.</a> Macromol. Rapid Commun. 8 (10), 481-485 (1987).</li><li>Yoshida, 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=Comb-type+grafted+hydrogels+with+rapid+deswelling+response+to+temperature+changes.">Comb-type grafted hydrogels with rapid deswelling response to temperature changes.</a> Nature. 374 (6519), 240-242 (1995).</li><li>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=Collapse+of+gels+and+the+critical+endpoint.">Collapse of gels and the critical endpoint.</a> Phys. Rev. Lett. 40 (12), 820-823 (1978).</li><li>Tanaka, 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=Phase+transitions+in+ionic+gels.">Phase transitions in ionic gels.</a> Phys. Rev. Lett. 45 (20), 1636-1639 (1980).</li><li>Zhao, Y. L., Stoddart, J. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Azobenzene-based+light-responsive+hydrogel+system.">Azobenzene-based light-responsive hydrogel system.</a> Langmuir. 25 (15), 8442-8446 (2009).</li><li>Alvarez-Lorenzo, C., Bromberg, L., Concheiro, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Light-sensitive+intelligent+drug+delivery+systems.">Light-sensitive intelligent drug delivery systems.</a> Photochem. 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. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fabrication+of+monodisperse+thermosensitive+microgels+and+gel+capsules+in+microfluidic+devices.">Fabrication of monodisperse thermosensitive microgels and gel capsules in microfluidic devices.</a> Soft Matter. 4 (12), 2303-2309 (2008).</li><li>Jack, C. R., Forbes, G., Dewanjee, M. K., Brown, M. L., Earnest, F. <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+sponge+for+embolotherapy:+particle+size+and+morphology.">Polyvinyl alcohol sponge for embolotherapy: particle size and morphology.</a> Am. J. Neuroradiol. 6 (4), 595-597 (1985).</li><li>Derdeyn, C. P., Moran, C. J., Cross, D. T., Dietrich, H. H., Dacey, R. 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. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Janus+supraparticles+by+induced+phase+separation+of+nanoparticles+in+droplets.">Janus supraparticles by induced phase separation of nanoparticles in droplets.</a> Adv. Mater. 21 (19), 1949-1953 (2009).</li><li>Lone, 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=Microfluidic+synthesis+of+Janus+particles+by+UV-directed+phase+separation.">Microfluidic synthesis of Janus particles by UV-directed phase separation.</a> Chem. 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. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Janus+microgels+produced+from+functional+precursor+polymers.">Janus microgels produced from functional precursor polymers.</a> Langmuir. 26 (18), 14842-14847 (2010).</li><li>Peppas, N. A., Hilt, J. Z., Khademhosseini, A., Langer, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrogels+in+biology+and+medicine:+from+molecular+principles+to+bionanotechnology.">Hydrogels in biology and medicine: from molecular principles to bionanotechnology.</a> Adv. Mater. 18 (11), 1345-1360 (2006).</li></ol>

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.

Research

JoVE Journal

Chemistry

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

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 ...

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 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 ...

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

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 ...

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 ...

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

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

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 ...

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 ...

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) ...