Name: synthesis of hydrogels with antifouling properties as membranes for water purification
Uploaded: 2017-04-07T14:00:00
Description: Watch this Scientific Journal Video about Synthesis of Hydrogels with Antifouling Properties As Membranes for Water Purification at JoVE.com

We gratefully acknowledge the financial support of this work by the Korean Carbon Capture and Sequestration R&amp;D Center (KCRC).

1. Preparation of the Prepolymer Solutions
<ol>
	<li>Preparation using water as a solvent
	<ol>
		<li>Add 10.00 g of deionized (DI) water to a glass bottle with a magnetic stir bar.</li>
		<li>Measure 2.00 g of SBMA and transfer it to the glass bottle containing the water. Stir the solution for 30 min, until the SBMA is completely dissolved.</li>
		<li>In a separate bottle, add 20.00 g of PEGDA (Mn = 700 g/mol).</li>
		<li>Add 20.0 mg of 1-hydroxycyclohexyl phenyl ketone (HCPK), a photo-init...

<ol>
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Polym. Sci. Part B Polym. Phys. 54 (19), 1924-1934 (2016).</li><li>Shao, Q., Jiang, S. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+Understanding+and+Design+of+Zwitterionic+Materials.">Molecular Understanding and Design of Zwitterionic Materials.</a> Adv Mat. 27 (1), 15-26 (2015).</li><li>Zhang, Z., Chao, T., Chen, S., Jiang, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Superlow+Fouling+Sulfobetaine+and+Carboxybetaine+Polymers+on+Glass+Slides.">Superlow Fouling Sulfobetaine and Carboxybetaine Polymers on Glass Slides.</a> Langmuir. 22 (24), 10072-10077 (2006).</li><li>Chen, S., Li, L., Zhao, C., Zheng, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface+hydration:+principles+and+applications+toward+low-fouling/nonfouling+biomaterials.">Surface hydration: principles and applications toward low-fouling/nonfouling biomaterials.</a> Polymer. 51 (23), 5283-5293 (2010).</li><li>Bengani, P., Kou, Y. M., Asatekin, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Zwitterionic+copolymer+self-assembly+for+fouling+resistant,+high+flux+membranes+with+size-based+small+molecule+selectivity.">Zwitterionic copolymer self-assembly for fouling resistant, high flux membranes with size-based small molecule selectivity.</a> J Membr Sci. 493, 755-765 (2015).</li><li>Chiang, Y. C., Chang, Y., Chuang, C. J., Ruaan, R. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+facile+zwitterionization+in+the+interfacial+modification+of+low+bio-fouling+nanofiltration+membranes.">A facile zwitterionization in the interfacial modification of low bio-fouling nanofiltration membranes.</a> J Membr Sci. 389, 76-82 (2012).</li><li>Mi, Y. F., Zhao, Q., Ji, Y. L., An, Q. F., Gao, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+route+for+surface+zwitterionic+functionalization+of+polyamide+nanofiltration+membranes+with+improved+performance.">A novel route for surface zwitterionic functionalization of polyamide nanofiltration membranes with improved performance.</a> J Membr Sci. 490, 311-320 (2015).</li><li>Shafi, H. Z., Khan, Z., Yang, R., Gleason, K. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface+modification+of+reverse+osmosis+membranes+with+zwitterionic+coating+for+improved+resistance+to+fouling.">Surface modification of reverse osmosis membranes with zwitterionic coating for improved resistance to fouling.</a> Desalination. 362, 93-103 (2015).</li><li>Yang, R., Goktekin, E., Gleason, K. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Zwitterionic+Antifouling+Coatings+for+the+Purification+of+High-Salinity+Shale+Gas+Produced+Water.">Zwitterionic Antifouling Coatings for the Purification of High-Salinity Shale Gas Produced Water.</a> Langmuir. 31 (43), 11895-11903 (2015).</li><li>Yang, R., Jang, H., Stocker, R., Gleason, K. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synergistic+Prevention+of+Biofouling+in+Seawater+Desalination+by+Zwitterionic+Surfaces+and+Low-Level+Chlorination.">Synergistic Prevention of Biofouling in Seawater Desalination by Zwitterionic Surfaces and Low-Level Chlorination.</a> Adv Mat. 26 (11), 1711-1718 (2014).</li><li>Azari, S., Zou, L. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Using+zwitterionic+amino+acid+L-DOPA+to+modify+the+surface+of+thin+film+composite+polyamide+reverse+osmosis+membranes+to+increase+their+fouling+resistance.">Using zwitterionic amino acid L-DOPA to modify the surface of thin film composite polyamide reverse osmosis membranes to increase their fouling resistance.</a> J Membr Sci. 401, 68-75 (2012).</li><li>Chang, 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=Underwater+Superoleophobic+Surfaces+Prepared+from+Polymer+Zwitterion/Dopamine+Composite+Coatings.">Underwater Superoleophobic Surfaces Prepared from Polymer Zwitterion/Dopamine Composite Coatings.</a> Adv Mater Inter. , (2016).</li><li>Lin, H., Kai, T., Freeman, B. D., Kalakkunnath, S., Kalika, 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=The+Effect+of+Cross-Linking+on+Gas+Permeability+in+Cross-Linked+Poly(Ethylene+Glycol+Diacrylate).">The Effect of Cross-Linking on Gas Permeability in Cross-Linked Poly(Ethylene Glycol Diacrylate).</a> Macromolecules. 38 (20), 8381-8393 (2005).</li><li>Sagle, A. C., Ju, H., Freeman, B. D., Sharma, M. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PEG-based+hydrogel+membrane+coatings.">PEG-based hydrogel membrane coatings.</a> Polymer. 50 (3), 756-766 (2009).</li><li>Wu, Y. -. H., Park, H. B., Kai, T., Freeman, B. D., Kalika, 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=Water+uptake,+transport+and+structure+characterization+in+poly(ethylene+glycol)+diacrylate+hydrogels.">Water uptake, transport and structure characterization in poly(ethylene glycol) diacrylate hydrogels.</a> J Membr Sci. 347 (1-2), 197-208 (2010).</li><li>Rahimpour, 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=Novel+functionalized+carbon+nanotubes+for+improving+the+surface+properties+and+performance+of+polyethersulfone+(PES)+membrane.">Novel functionalized carbon nanotubes for improving the surface properties and performance of polyethersulfone (PES) membrane.</a> Desalination. 286, 99-107 (2012).</li><li>Gulmine, J. V., Janissek, P. R., Heise, H. M., Akcelrud, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polyethylene+characterization+by+FTIR.">Polyethylene characterization by FTIR.</a> Polym Testing. 21 (5), 557-563 (2002).</li><li>Ara&#250;jo, J. R., Waldman, W. R., De Paoli, 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=Thermal+properties+of+high+density+polyethylene+composites+with+natural+fibres:+Coupling+agent+effect.">Thermal properties of high density polyethylene composites with natural fibres: Coupling agent effect.</a> Polym. Degrad. Stab. 93 (10), 1770-1775 (2008).</li><li>McCloskey, B. D., 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=Influence+of+polydopamine+deposition+conditions+on+pure+water+flux+and+foulant+adhesion+resistance+of+reverse+osmosis,+ultrafiltration,+and+microfiltration+membranes.">Influence of polydopamine deposition conditions on pure water flux and foulant adhesion resistance of reverse osmosis, ultrafiltration, and microfiltration membranes.</a> Polymer. 51 (15), 3472-3485 (2010).</li></ol>

We have demonstrated a facile method to prepare freestanding films and impregnated membranes based on zwitterionic hydrogels. The disappearance of three (meth)acrylate characteristic peaks (i.e., 810, 1,190, and 1,410 cm-1) in the IR spectra of the obtained polymer films and impregnated membrane (Figure 2) indicates the good conversion of the monomers and crosslinker4,19,21. Additionally, the...

There is a great need to develop low cost and energy efficient technologies to produce clean water in order to meet the increasing demand. Polymeric membranes have emerged as a leading technology for water purification due to their inherent advantages, such as their high energy efficiency, low cost, and simplicity in operation1. Membranes allow pure water to permeate through and reject the contaminants. However, membranes are often subjected to fouling by contaminants in the feed water, which can be adsorbed onto the membrane surface from their favorable interactions2,3. The fouling can dramatically decrease water flux through the membranes, increasing the membrane area required and the cost of water purification.
An effective approach to mitigate fouling is to modify the membrane surface to increase the hydrophilicity and thus decrease the favorable interactions between the membrane surface and foulants. One method is to use thin-film coating with superhydrophilic3 hydrogels. The hydrogels often have high water permeability; therefore, a thin-film coating can increase the long-term water permeance through the membrane due to the mitigated fouling, despite the slightly increased transport resistance across the whole membrane. The hydrogels can also be directly fabricated into impregnated membranes for water purification in osmotic applications4.
Zwitterionic materials contain both positively and negatively charged functional groups, with a net neutral charge, and have strong surface hydration through electrostatic-induced hydrogen bonding5,6,7,8,9. The tightly bound hydration layers act as physical and energy barriers, preventing foulants from attaching onto the surface, thus demonstrating excellent antifouling properties10. Zwitterionic polymers, such as poly(sulfobetaine methacrylate) (PSBMA) and poly(carboxybetaine methacrylate) (PCBMA), have been used to modify the membrane surface by coating11,12,13,14,15,16,17,18 to increase surface hydrophilicity and thus antifouling properties.
We demonstrate here a facile method to prepare zwitterionic hydrogels using sulfobetaine methacrylate (SBMA) via photopolymerization, which is crosslinked using poly(ethylene glycol) diacrylate (PEGDA, Mn = 700 g/mol) to improve the mechanical strength. We also present a procedure to construct robust membranes by impregnating the monomer and crosslinker in a highly porous hydrophobic support before the photopolymerization. The physical and water transport properties of the freestanding films and impregnated membranes are thoroughly characterized to elucidate the structure/property relationship for water purification. The prepared hydrogels can be used as a surface coating to enhance membrane separation properties. By adjusting the crosslinking density or by impregnating into hydrophobic porous supports, these materials can also form thin films with sufficient mechanical strength for osmotic processes, such as forward osmosis or pressure-retarded osmosis4.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Poly(ethylene glycol) diacrylate&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; Mn = 700 (PEGDA)</td>
			<td>Sigma Aldrich</td>
			<td>455008</td>
			<td></td>
		</tr>
		<tr>
			<td>1-Hydroxycyclohexyl phenyl ketone, 99% (HCPK)</td>
			<td>Sigma Aldrich</td>
			<td>405612</td>
			<td></td>
		</tr>
		<tr>
			<td>[2-(Methacrloyloxy)ethyl dimethyl-(3-sulfopropyl) ammonium hydroxide, 97%</td>
			<td>Sigma Aldrich</td>
			<td>537284</td>
			<td>Acutely Toxic</td>
		</tr>
		<tr>
			<td>Ethanol, 95%</td>
			<td>Koptec, VWR International</td>
			<td>V1101</td>
			<td>Flamable</td>
		</tr>
		<tr>
			<td>Decane, anhydrous, 99%</td>
			<td>Sigma Aldrich</td>
			<td>457116</td>
			<td></td>
		</tr>
		<tr>
			<td>Solupor Membrane</td>
			<td>Lydall</td>
			<td>7PO7D</td>
			<td></td>
		</tr>
		<tr>
			<td>Micrometer&#160;</td>
			<td>Starrett</td>
			<td>2900-6</td>
			<td></td>
		</tr>
		<tr>
			<td>ATR-FTIR</td>
			<td>Vertex 70</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>DSC: TA Q2000</td>
			<td>TA Instruments</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Rame&#8217;-hart Goniometer: Model 190</td>
			<td>Rame&#8217;-hart Instruments</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Ultraviolet Crosslinker: CX-2000</td>
			<td>Ultra-Violet Products</td>
			<td></td>
			<td>UV radiation&#160;</td>
		</tr>
		<tr>
			<td>Permeation Cell: Model UHP-43</td>
			<td>Advantec MFS</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Deionized Water: Milli-Q Water</td>
			<td>EMD Millipore</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

synthesis of hydrogels with antifouling properties as membranes for water purification

Hydrogels have been widely utilized to enhance the surface hydrophilicity of membranes for water purification, increasing the antifouling properties and thus achieving stable water permeability through membranes over time. Here, we report a facile method to prepare hydrogels based on zwitterions for membrane applications. Freestanding films can be prepared from sulfobetaine methacrylate (SBMA) with a crosslinker of poly(ethylene glycol) diacrylate (PEGDA) via photopolymerization. The hydrogels can also be prepared by impregnation into hydrophobic porous supports to enhance the mechanical strength. These films can be characterized by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) to determine the degree of conversion of the (meth)acrylate groups, using goniometers for hydrophilicity and differential scanning calorimetry (DSC) for polymer chain dynamics. We also report protocols to determine the water permeability in dead-end filtration systems and the effect of foulants (bovine serum albumin, BSA) on membrane performance.

Freestanding films prepared with the prepolymer solutions specified in steps 1.1 and 1.2 are referred to as S50 and S30, respectively. Detailed information is shown in Table 1. The prepolymer solution specified in step 1.2 was also used to fabricate impregnated membranes, which are denoted as IMS30. Because the porous support is made of hydrophobic polyethylene, only the prepolymer solution containing ethanol can be impre...

Watch this Scientific Journal Video about Synthesis of Hydrogels with Antifouling Properties As Membranes for Water Purification at JoVE.com

Synthesis of Hydrogels with Antifouling Properties As Membranes for Water Purification

This paper reports practical methods to prepare hydrogels in freestanding films and impregnated membranes and to characterize their physical properties, including water transport properties.

Hydrogels have been widely utilized to enhance the surface hydrophilicity of membranes for water purification, increasing the antifouling properties and ...

The overall goal of this procedure is to prepare and characterize freestanding films and impregnated membranes based on zwitterionic hydrogels for membrane water purification. This method provide guidance for repairing hydrogel base freestanding film in impregnated membrane and as well as for characterizing their physical and transport properties. The main advantage of this technique is that it's simple, fast, and easy to be scaled up in industrial production.Visual demonstration of this method is critical as the integrated hydrogel preparation and characterization steps are difficult to learn because custom built apparatus is used, and interdisciplinary skills are required. To prepare the freestanding films, first place two spacers of known thickness on a clean quartz disc. The thickness of the spacers controls the thickness of the obtained polymer films.Transfer a small amount of the pre-polymer solution to the quartz disc using a disposable pipette. Place another quartz disc on top of the liquid and ensure that there are no bubbles in the liquid film. Then, place the sample in an ultraviolet or UV crosslinker and irradiate it for five minutes using UV light with a wavelength of 254 nanometers.When the polymer film is removed from the quartz disc, it is critical to work slowly to avoid tearing the film. Separate the polymer film from the quartz discs using a sharp blade. Use tweezers to transfer the film to a deionized water bath.Change the water twice during the first 24 hours to remove the solvent, unreacted monymer and crosslinker, and solve from the film. To prepare dried films for analysis, remove the film from the water bath and allow it to air dry for 24 hours. Place the film in a vacuum oven at 80 degrees Celsius to dry overnight under vacuum.Place a sheet of porous support onto a quartz disc. Using a foam brush, coat each side of the support twice with a prepolymer solution that is based on the water ethanol mixture. Place another quartz disc on top of the support.Then place the sample in a UV crosslinker and irradiate it for five minutes using UV light with a wavelength of 254 nanometers. To remove the impregnated membrane from the quartz discs, immerse the whole assembly in a deionized water bath for five minutes and carefully remove the membrane using a sharp blade and tweezers. Keeping the membrane in deionized water, change the water twice to remove the solvent, the unreacted monymer and crosslinker, and the sol from the membrane.To prepare dried, impregnated membranes for analysis, remove the membrane from the water bath, allow the membrane to dry at ambient conditions for 24 hours. Then, dry the membrane in a vacuum oven overnight at 80 degrees Celsius under vacuum. To measure the contact angles using the pendant drop method, first cut a rectangular strip of the membrane sample.Soak this strip in deionized water for 10 minutes. And then dry it for five minutes. Place the dried sample on the sample holder.Then, submerge the sample holder in a transparent environmental chamber containing the deionized water. In the next step, it is critical to work slowly and dispensing the n-decane drops onto the membranes. Using a microliter syringe with a stainless steel needle, dispense drops of n-decane onto the membrane sample.Leave the setup undisturbed for two minutes to ensure the stabilization of the droplets. Next, use appropriate image analysis software to determine the contact angle of the samples by measuring the angles of the dispensed droplets on the membrane surface. To characterize the water permeability using a dead end filtration system, first cut coupons of freestanding films and impregnated membranes with a hammer driven hole punch of an appropriate diameter.Place a prepared coupon on the porous support inside a dead end filtration cell. Then, place the O ring on top of the sample. Screw the two halves of the permeation cell together.Next, add approximately 50 milliliters of deonized water to the permeation cell. Screw on the cap and place the permeation cell on a magnetic stirrer. Set the stirring rate to between 300 and 900 RPM.Then, place a covered beaker on a balance to collect the permeate water and tear the balance. Open the valve on the gas cylinder. Turn the pressure regulator valve clockwise until the desired pressure is reached.Finally, open the release valve to deliver the pressure to the permeation cell. Monitor and record the weight of the beaker with time. Shown here are photos of the freestanding film, porous support, and impregnated membranes.It is evidence that after the porous support is filled with the hydrogel, it changes from opaque to transparent. The infrared spectra indicate the almost complete conversion of the acryllate groups in the hydrogels. Due to the absence of acryllate characteristic peaks in the spectra.The glass transition temperature of hydrogels is determined by differential scan calorimetry as shown here. Lower contact angles in the freestanding films and impregnated membranes indicate the greater hydrophilicity than the porous support. After watching this video you should have a good understanding of how to repair hydrogel base materials and characterize their properties.This work describes a faster method to fabricate hydrogel based material via photopolymerizations as well as how to characterize them for water purification. The method and material may also be used to repair membrane for gas operations such as CO2 capture. Don't forget that working with chemical and UV radiation can be extremely hazardous and precautions such as personal protective equipment should always be taken while performing this procedure.

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Research

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Bioengineering

Preparation of Light-responsive Membranes by a Combined Surface Grafting and Postmodification Process

In order to modify the surface tension of commercial available track-edged polymer membranes, a procedure of surface-initiated polymerization is presented. The polymerization from the membrane surface is induced by plasma treatment of the membrane, followed by reacting the membrane surface with a methanolic solution of 2-hydroxyethyl methacrylate (HEMA). Special attention is given to the process parameters for the plasma treatment prior to the polymerization on the surface. For example, the influence of the plasma-treatment on different types of membranes (e.g.&#160;polyester, polycarbonate, polyvinylidene fluoride) is studied. Furthermore, the time-dependent stability of the surface-grafted membranes is shown by contact angle measurements. When grafting poly(2-hydroxyethyl methacrylate) (PHEMA) in this way, the surface can be further modified by esterification of the alcohol moiety of the polymer with a carboxylic acid function of the desired substance. These reactions can therefore be used for the functionalization of the membrane surface. For example, the surface tension of the membrane can be changed or a desired functionality as the presented light-responsiveness can be inserted. This is demonstrated by reacting PHEMA with a carboxylic acid functionalized spirobenzopyran unit which leads to a light-responsive membrane. The choice of solvent plays a major role in the postmodification step and is discussed in more detail in this paper. The permeability measurements of such functionalized membranes are performed using a Franz cell with an external light source. By changing the wavelength of the light from the visible to the UV-range, a change of permeability of aqueous caffeine solutions is observed.

A plasma-induced polymerization procedure is described for the surface-initiated polymerization on polymer membranes. Further postmodification of the grafted polymer with photochromic substances is presented with a protocol of conducting permeability measurements of light-responsive membranes.

In order to modify the surface tension of commercial available track-edged polymer membranes, a procedure of surface-initiated polymerization is ...

Combination of Microstereolithography and Electrospinning to Produce Membranes Equipped with Niches for Corneal Regeneration

Corneal problems affect millions of people worldwide reducing their quality of life significantly. Corneal disease can be caused by illnesses such as Aniridia or Steven Johnson Syndrome as well as by external factors such as chemical burns or radiation. Current treatments are (i) the use of corneal grafts and (ii) the use of stem cell expanded in the laboratory and delivered on carriers (e.g., amniotic membrane); these treatments are relatively successful but unfortunately they can fail after 3-5 years. There is a need to design and manufacture new corneal biomaterial devices able to mimic in detail the physiological environment where stem cells reside in the cornea. Limbal stem cells are located in the limbus (circular area between cornea and sclera) in specific niches known as the Palisades of Vogt. In this work we have developed a new platform technology which combines two cutting-edge manufacturing techniques (microstereolithography and electrospinning) for the fabrication of corneal membranes that mimic to a certain extent the limbus. Our membranes contain artificial micropockets which aim to provide cells with protection as the Palisades of Vogt do in the eye.

We report a technique for the fabrication of micropockets within electrospun membranes in which to study cell behavior. Specifically, we describe a combination of microstereolithography and electrospinning for the production of PLGA (Poly(lactide-co-glycolide)) corneal biomaterial devices equipped with microfeatures.

Corneal problems affect millions of people worldwide reducing their quality of life significantly. Corneal disease can be caused by illnesses such as ...

Three-Dimensionally Printed Microfluidic Cross-flow System for Ultrafiltration/Nanofiltration Membrane Performance Testing

Minimization and management of membrane fouling is a formidable challenge in diverse industrial processes and other practices that utilize membrane technology. Understanding the fouling process could lead to optimization and higher efficiency of membrane based filtration. Here we show the design and fabrication of an automated three-dimensionally (3-D) printed microfluidic cross-flow filtration system that can test up to 4 membranes in parallel. The microfluidic cells were printed using multi-material photopolymer 3-D printing technology, which used a transparent hard polymer for the microfluidic cell body and incorporated a thin rubber-like polymer layer, which prevents leakages during operation. The performance of ultrafiltration (UF), and nanofiltration (NF) membranes were tested and membrane fouling could be observed with a model foulant bovine serum albumin (BSA). Feed solutions containing BSA showed flux decline of the membrane. This protocol may be extended to measure fouling or biofouling with many other organic, inorganic or microbial containing solutions. The microfluidic design is especially advantageous for testing materials that are costly or only available in small quantities, for example polysaccharides, proteins, or lipids due to the small surface area of the membrane being tested. This modular system may also be easily expanded for high throughput testing of membranes.&#160;

Design and fabrication of a three-dimensionally (3-D) printed microfluidic cross-flow filtration system is demonstrated. The system is used to test performance and observe fouling of ultrafiltration and nanofiltration (thin film composite) membranes.

Minimization and management of membrane fouling is a formidable challenge in diverse industrial processes and other practices that utilize membrane ...

Transport Properties of Ibuprofen Encapsulated in Cyclodextrin Nanosponge Hydrogels: A Proton HR-MAS NMR Spectroscopy Study

The chemical cross-linking of &#946;-cyclodextrin (&#946;-CD) with ethylenediaminetetraacetic dianhydride (EDTA) led to branched polymers referred to as cyclodextrin nanosponges (CDNSEDTA). Two different preparations are described with 1:4 and 1:8 CD-EDTA molar ratios. The corresponding cross-linked polymers were contacted with 0.27 M aqueous solution of ibuprofen sodium salt (IP) leading to homogeneous, colorless, drug loaded hydrogels.
The systems were characterized by high resolution magic angle spinning (HR-MAS) NMR spectroscopy. Pulsed field gradient spin echo (PGSE) NMR spectroscopy was used to determine the mean square displacement (MSD) of IP inside the polymeric gel at different observation times td. The data were further processed in order to study the time dependence of MSD: MSD = f(td). The proposed methodology is useful to characterize the different diffusion regimes that, in principle, the solute may experience inside the hydrogel, namely normal or anomalous diffusion. The full protocols including the polymer preparation and purification, the obtainment of drug-loaded hydrogels, the NMR sample preparation, the measurement of MSD by HR-MAS NMR spectroscopy and the final data processing to achieve the time dependence of MSD are here reported and discussed. The presented experiments represent a paradigmatic case and the data are discussed in terms of innovative approach to the characterization of the transport properties of an encapsulated guest within a polymeric host of potential application for drug delivery.

The motion regimes of ibuprofen encapsulated in &#946;-cyclodextrin nanosponges polymer network are investigated using pulsed-field-gradient spin-echo (PGSE) NMR technique. Synthesis, purification, drug loading, implementation of the NMR pulse sequence and data analysis to work out the mean square displacement of the drug at several observation times are described in detail.

The chemical cross-linking of &#946;-cyclodextrin (&#946;-CD) with ethylenediaminetetraacetic dianhydride (EDTA) led to branched polymers referred to as ...

The Synthesis of RGD-functionalized Hydrogels as a Tool for Therapeutic Applications

The use of polymers as biomaterials has provided significant advantages in therapeutic applications. In particular, the possibility to modify and functionalize polymer chains with compounds that are able to improve biocompatibility, mechanical properties, or cell viability allows the design of novel materials to meet new challenges in the biomedical field. With the polymer functionalization strategies, click chemistry is a powerful tool to improve cell-compatibility and drug delivery properties of polymeric devices. Similarly, the fundamental need of biomedicine to use sterile tools to avoid potential adverse-side effects, such as toxicity or contamination of the biological environment, gives rise to increasing interest in the microwave-assisted strategy.
The combination of click chemistry and the microwave-assisted method is suitable to produce biocompatible hydrogels with desired functionalities and improved performances in biomedical applications. This work aims to synthesize RGD-functionalized hydrogels. RGD (arginylglycylaspartic acid) is a tripeptide that can mimic cell adhesion proteins and bind to cell-surface receptors, creating a hospitable microenvironment for cells within the 3D polymeric network of the hydrogels. RGD functionalization occurs through Huisgen 1,3-dipolar cycloaddition. Some PAA carboxyl groups are modified with an alkyne moiety, whereas RGD is functionalized with azido acid as the terminal residue of the peptide sequence. Finally, both products are used in a copper catalyzed click reaction to permanently link the peptide to PAA. This modified polymer is used with carbomer, agarose and polyethylene glycol (PEG) to synthesize a hydrogel matrix. The 3D structure is formed due to an esterification reaction involving carboxyl groups from PAA and carbomer and hydroxyl groups from agarose and PEG through microwave-assisted polycondensation. The efficiency of the gelation mechanism ensures a high degree of RGD functionalization. In addition, the procedure to load therapeutic compounds or biological tools within this functionalized network is very simple and reproducible.

We present a protocol for the synthesis of RGD-functionalized hydrogels as devices for cell and drug delivery. The procedure involves copper catalyzed alkyne-azide cycloaddition (CuAAC) between alkyne-modified polyacrylic acid (PAA) and a RGD-azide derivative. The hydrogels are formed using microwave-assisted polycondensation and their physicochemical properties are investigated.

The use of polymers as biomaterials has provided significant advantages in therapeutic applications. In particular, the possibility to modify and ...

Synthesis of Biocompatible Liquid Crystal Elastomer Foams as Cell Scaffolds for 3D Spatial Cell Cultures

Here, we present a step-by-step preparation of a 3D, biodegradable, foam-like cell scaffold. These scaffolds were prepared by cross-linking star block co-polymers featuring cholesterol units as side-chain pendant groups, resulting in smectic-A (SmA) liquid crystal elastomers (LCEs). Foam-like scaffolds, prepared using metal templates, feature interconnected microchannels, making them suitable as 3D cell culture scaffolds. The combined properties of the regular structure of the metal foam and of the elastomer result in a 3D cell scaffold that promotes not only higher cell proliferation compared to conventional porous templated films, but also better management of mass transport (i.e., nutrients, gases, waste, etc.). The nature of the metal template allows for the easy manipulation of foam shapes (i.e., rolls or films) and for the preparation of scaffolds of different pore sizes for different cell studies while preserving the interconnected porous nature of the template. The etching process does not affect the chemistry of the elastomers, preserving their biocompatible and biodegradable nature. We show that these smectic LCEs, when grown for extensive time periods, enable the study of clinically relevant and complex tissue constructs while promoting the growth and proliferation of cells.

This study presents a methodology to prepare 3D, biodegradable, foam-like cell scaffolds based on biocompatible side-chain liquid crystal elastomers (LCEs). Confocal microscopy experiments show that foam-like LCEs allow for cell attachment, proliferation, and the spontaneous alignment of C2C12s myoblasts.

Here, we present a step-by-step preparation of a 3D, biodegradable, foam-like cell scaffold. These scaffolds were prepared by cross-linking star block ...

Ultrathin Porated Elastic Hydrogels As a Biomimetic Basement Membrane for Dual Cell Culture

The basement membrane is a critical component of cellular bilayers that can vary in stiffness, composition, architecture, and porosity. In vitro studies of endothelial-epithelial bilayers have traditionally relied on permeable support models that enable bilayer culture, but permeable supports are limited in their ability to replicate the diversity of human basement membranes. In contrast, hydrogel models that require chemical synthesis are highly tunable and allow for modifications of both the material stiffness and the biochemical composition via incorporation of biomimetic peptides or proteins. However, traditional hydrogel models are limited in functionality because they lack pores for cell-cell contacts and functional in vitro migration studies. Additionally, due to the thickness of traditional hydrogels, incorporation of pores that span the entire thickness of hydrogels has been challenging. In the present study, we use poly-(ethylene-glycol) (PEG) hydrogels and a novel zinc oxide templating method to address the previous shortcomings of biomimetic hydrogels. As a result, we present an ultrathin, basement membrane-like hydrogel that permits the culture of confluent cellular bilayers on a customizable scaffold with variable pore architectures, mechanical properties, and biochemical composition.

Current bilayer culture models do not allow for functional in vitro studies that mimic in vivo microenvironments. Using polyethylene glycol and a zinc oxide templating method, this protocol describes the development of an ultrathin biomimetic basement membrane with tunable stiffness, porosity, and biochemical composition that closely mimics in vivo extracellular matrices.

The basement membrane is a critical component of cellular bilayers that can vary in stiffness, composition, architecture, and porosity. In vitro studies ...

Synthesis of Multi-walled Carbon Nanotubes Modified with Silver Nanoparticles and Evaluation of Their Antibacterial Activities and Cytotoxic Properties

In this study, multi-walled carbon nanotubes (MWCNTs) were treated with an aqueous sulfuric acid solution to form an oxygen-based functional group. Silver MWCNTs were prepared by the reductive deposition of silver from an aqueous solution of AgNO3 on the oxidized MWCNTs. Given the unique color of the CNTs, it was not possible to apply them to the minimum inhibitory concentration or mitochondrial toxicity assays to evaluate the toxicity and antibacterial properties, since they would interfere with the assays. The inhibition zone and minimum bactericidal concentration for the Ag-MWCNTs were measured and Live/Dead and Trypan Blue assays were used to measure the toxicity and antibacterial properties without interfering with the color of the CNTs.

In this study, antimicrobial nanomaterials were synthesized by acidic oxidation of multiwalled carbon nanotubes and subsequent reductive deposition of silver nanoparticles. Antimicrobial activity and cytotoxicity tests were performed with the as-prepared nanomaterials.

In this study, multi-walled carbon nanotubes (MWCNTs) were treated with an aqueous sulfuric acid solution to form an oxygen-based functional group. Silver ...

Immobilization of Live Caenorhabditis elegans Individuals Using an Ultra-thin Polydimethylsiloxane Microfluidic Chip with Water Retention

Radiation is widely used for biological applications and for ion-beam breeding, and among these methods, microbeam irradiation represents a powerful means of identifying radiosensitive sites in living organisms. This paper describes a series of on-chip immobilization methods developed for the targeted microbeam irradiation of live individuals of Caenorhabditis elegans. Notably, the treatment of the polydimethylsiloxane (PDMS) microfluidic chips that we previously developed to immobilize C. elegans individuals without the need for anesthesia is explained in detail. This chip, referred to as a worm sheet, is resilient to allow the microfluidic channels to be expanded, and the elasticity allows animals to be enveloped gently. Also, owing to the self-adsorption capacity of the PDMS, animals can be sealed in the channels by covering the surface of the worm sheet with a thin cover film, in which animals are not pushed into the channels for enclosure. By turning the cover film over, we can easily collect the animals. Furthermore, the worm sheet shows water retention and allows C. elegans individuals to be subjected to microscopic observation for long periods under live conditions. In addition, the sheet is only 300 &#181;m thick, allowing heavy ions such as carbon ions to pass through the sheet enclosing the animals, thus allowing the ion particles to be detected and the applied radiation dose to be measured accurately. Because selection of the cover films used for enclosing the animals is very important for successful long-term immobilization, we conducted the selection of the suitable cover films and showed a recommended one among some films. As an application example of the chip, we introduced imaging observation of muscular activities of animals enclosing the microfluidic channel of the worm sheet, as well as the microbeam irradiation. These examples indicate that the worm sheets have greatly expanded the possibilities for biological experiments.

Immobilization of Live Caenorhabditis elegans Individuals Using an Ultra-thin Polydimethylsiloxane Microfluidic Chip with Water Retention

A series of immobilization methods has been established to allow the targeted irradiation of live Caenorhabditis elegans individuals using a recently developed ultra-thin polydimethylsiloxane microfluidic chip with water retention. This novel on-chip immobilization is also adequate for imaging observations. The detailed treatment and application examples of the chip are explained.

Radiation is widely used for biological applications and for ion-beam breeding, and among these methods, microbeam irradiation represents a powerful means ...

Controlled Strain of 3D Hydrogels under Live Microscopy Imaging

External forces are an important factor in tissue formation, development, and maintenance. The effects of these forces are often studied using specialized in vitro stretching methods. Various available systems use 2D substrate-based stretchers, while the accessibility of 3D techniques to strain soft hydrogels, is more restricted. Here, we describe a method that allows external stretching of soft hydrogels from their circumference, using an elastic silicone strip as the sample carrier. The stretching system utilized in this protocol is constructed from 3D-printed parts and low-cost electronics, making it simple and easy to replicate in other labs. The experimental process begins with polymerizing thick (&#62;100 &#956;m) soft fibrin hydrogels (Elastic Modulus of ~100 Pa) in a cut-out at the center of a silicone strip. Silicone-gel constructs are then attached to the printed-stretching device and placed on the confocal microscope stage. Under live microscopy the stretching device is activated, and the gels are imaged at various stretch magnitudes. Image processing is then used to quantify the resulting gel deformations, demonstrating relatively homogenous strains and fiber alignment throughout the gel&#8217;s 3D thickness (Z-axis). Advantages of this method include the ability to strain extremely soft hydrogels in 3D while executing in situ microscopy, and the freedom to manipulate the geometry and size of the sample according to the user&#8217;s needs. Additionally, with proper adaptation, this method can be used to stretch other types of hydrogels (e.g., collagen, polyacrylamide or polyethylene glycol) and can allow for analysis of cells and tissue response to external forces under more biomimetic 3D conditions.

The presented method involves uniaxial stretching of 3D soft hydrogels embedded in silicone rubber while allowing live confocal microscopy. Characterization of the external and internal hydrogel strains as well as fiber alignment are demonstrated. The device and protocol developed can assess the response of cells to various strain regimes.

External forces are an important factor in tissue formation, development, and maintenance. The effects of these forces are often studied using specialized ...