Name: interlinked macroporous 3d scaffolds from microgel rods
Uploaded: 2022-06-16T13:30:00
Description: Watch this Scientific Journal Video about Interlinked Macroporous 3D Scaffolds from Microgel Rods at JoVE.com

We express our gratitude to the coauthors of our previous work this methodology is based on, C&#233;line Bastard, Luis P. B. Guerzoni, Yonca Kittel, Rostislav Vinokur, Nikolai Born, and Tam&#225;s Haraszti. We gratefully acknowledge funding from the Deutsche Forschungsgemeinschaft (DFG) within the project B5 and C3 SFB 985 &#34;Functional Microgels and Microgel Systems&#34;. We acknowledge funding from the Leibniz Senate Competition Committee (SAW) under the Professorinnenprogramm (SAW-2017-PB62: BioMat). We sincerely acknowledge funding from the European Commission (EUSMI, 731019). This work was performed in part at the Center for Chemical Polymer Technology (CPT), which was supported by the EU and the federal state of North Rhine-Westphalia (grant EFRE 30 00 883 02).

1. Required material and preparations for microfluidics
<ol>
	<li>For the described microfluidic procedure, use 1 mL and 5 mL glass syringes and syringe pumps. On-chip droplet formation is observed via an inverted microscope equipped with a high-speed camera.</li>
	<li>Create the microfluidic chip design (Figure 1B) using a computer-aided design software and produce a master template as already reported12.</li>
	<li>Achieve controlled UV-irradiation...

<ol>
	<li>Daly, A. C., Riley, L., Segura, T., Burdick, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrogel+microparticles+for+biomedical+applications.">Hydrogel microparticles for biomedical applications.</a> Nature Reviews Materials. 5 (1), 20-43 (2020).</li><li>Griffin, D. R., Weaver, W. M., Scumpia, P. O., Di Carlo, D., Segura, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Accelerated+wound+healing+by+injectable+microporous+gel+scaffolds+assembled+from+annealed+building+blocks.">Accelerated wound healing by injectable microporous gel scaffolds assembled from annealed building blocks.</a> Nature Materials. 14 (7), 737-744 (2015).</li><li>Xin, S., Wyman, O. M., Alge, D. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assembly+of+PEG+microgels+into+porous+cell-instructive+3D+scaffolds+via+thiol-ene+click+chemistry.">Assembly of PEG microgels into porous cell-instructive 3D scaffolds via thiol-ene click chemistry.</a> Advanced Healthcare Materials. 7 (11), 1800160 (2018).</li><li>Truong, N. F., 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=Microporous+annealed+particle+hydrogel+stiffness,+void+space+size,+and+adhesion+properties+impact+cell+proliferation,+cell+spreading,+and+gene+transfer.">Microporous annealed particle hydrogel stiffness, void space size, and adhesion properties impact cell proliferation, cell spreading, and gene transfer.</a> Acta Biomaterialia. 94, 160-172 (2019).</li><li>Sheikhi, 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=Microfluidic-enabled+bottom-up+hydrogels+from+annealable+naturally-derived+protein+microbeads.">Microfluidic-enabled bottom-up hydrogels from annealable naturally-derived protein microbeads.</a> Biomaterials. 192, 560-568 (2019).</li><li>de Rutte, J. M., Koh, J., Di Carlo, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Scalable+high-throughput+production+of+modular+microgels+for+in+situ+assembly+of+microporous+tissue+scaffolds.">Scalable high-throughput production of modular microgels for in situ assembly of microporous tissue scaffolds.</a> Advanced Functional Materials. 29 (25), 1900071 (2019).</li><li>Hsu, R. -. 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=Adaptable+microporous+hydrogels+of+propagating+NGF-gradient+by+injectable+building+blocks+for+accelerated+axonal+outgrowth.">Adaptable microporous hydrogels of propagating NGF-gradient by injectable building blocks for accelerated axonal outgrowth.</a> Advanced Science. 6 (16), 1900520 (2019).</li><li>Caldwell, A. S., Campbell, G. T., Shekiro, K. M. T., Anseth, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clickable+microgel+scaffolds+as+platforms+for+3D+cell+encapsulation.">Clickable microgel scaffolds as platforms for 3D cell encapsulation.</a> Advanced Healthcare Materials. 6 (15), 1700254 (2017).</li><li>Chen, Z., 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=Advanced+microfluidic+devices+for+fabricating+multi-structural+hydrogel+microsphere.">Advanced microfluidic devices for fabricating multi-structural hydrogel microsphere.</a> Exploration. 1 (3), 20210036 (2021).</li><li>Qazi, T. H., 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=Anisotropic+rod-shaped+particles+influence+injectable+granular+hydrogel+properties+and+cell+invasion.">Anisotropic rod-shaped particles influence injectable granular hydrogel properties and cell invasion.</a> Advanced Materials. 34 (12), 2109194 (2022).</li><li>Rommel, 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=Functionalized+microgel+rods+interlinked+into+soft+macroporous+structures+for+3D+cell+culture.">Functionalized microgel rods interlinked into soft macroporous structures for 3D cell culture.</a> Advanced Science. 9 (10), 2103554 (2022).</li><li>Guerzoni, L. P. B., 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=Cell+encapsulation+in+soft,+anisometric+poly(ethylene)+glycol+microgels+using+a+novel+radical-free+microfluidic+system.">Cell encapsulation in soft, anisometric poly(ethylene) glycol microgels using a novel radical-free microfluidic system.</a> Small. 15 (20), 1900692 (2019).</li><li>Kr&#252;ger, A. J. 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=Compartmentalized+jet+polymerization+as+a+high-resolution+process+to+continuously+produce+anisometric+microgel+rods+with+adjustable+size+and+stiffness.">Compartmentalized jet polymerization as a high-resolution process to continuously produce anisometric microgel rods with adjustable size and stiffness.</a> Advanced Materials. 31 (49), 1903668 (2019).</li><li>Darling, N. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Click+by+click+microporous+annealed+particle+(MAP)+scaffolds.">Click by click microporous annealed particle (MAP) scaffolds.</a> Advanced Healthcare Materials. 9 (10), 1901391 (2020).</li><li>Lutzweiler, G., Ndreu Halili, ., Engin Vrana, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+overview+of+porous,+bioactive+scaffolds+as+instructive+biomaterials+for+tissue+regeneration+and+their+clinical+translation.">The overview of porous, bioactive scaffolds as instructive biomaterials for tissue regeneration and their clinical translation.</a> Pharmaceutics. 12 (7), 602 (2020).</li><li>Dang, H. P., 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=3D+printed+dual+macro-,+microscale+porous+network+as+a+tissue+engineering+scaffold+with+drug+delivering+function.">3D printed dual macro-, microscale porous network as a tissue engineering scaffold with drug delivering function.</a> Biofabrication. 11 (3), 035014 (2019).</li><li>Highley, C. B., Song, K. H., Daly, A. C., Burdick, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Jammed+microgel+inks+for+3D+printing+applications.">Jammed microgel inks for 3D printing applications.</a> Advanced Science. 6 (1), 1801076 (2019).</li></ol>

One of the critical steps in this protocol is the quality of the 2-aminoethyl methacrylate (AMA) used as the comonomer for primary amine functionalization. The AMA should be a fine-grained and preferably colorless powder delivered in a gas-tight brown glass container. One should avoid using greenish and lumpy material, as it significantly impairs the gelation reaction and negatively affects the reproducibility of the results. In case of poor gelation and unstable microgel rods, one can consider changing the supplier....

To study complex cooperative cell behavior in 3D constructs, scaffold platforms need to show consistent performance in reproducibility, have suitable geometry for cell migration, and, at the same time, allow certain flexibility in terms of parameter alteration to investigate their influence on the living tissue1. In recent years, the concept of macroporous annealed particles (MAP), first described by Segura et al., developed into an efficient and versatile platform for 3D scaffold production2. The tailored composition of the microgels, which are the building blocks of the final 3D scaffold, predefines properties such as the stiffness of the construct, the selective chemical reactivity of the gel network, and the final pore size of the scaffold2,3,4,5,6. Cell adhesive peptides as cues for scaffold-cell interactions are incorporated into the polymer network of the microgels to allow for cell attachment and can be varied to investigate their specific effects on cells in culture. The 3D scaffolds are stabilized by interlinking of the annealed injectable microgels due to covalent or supramolecular bonds, resulting in robust and defined constructs for cell culture2,3,5,7,8.
Microfluidics has established itself as one of the most accurate and adaptable methods for the preparation of defined granular hydrogels9. The possibility of producing larger quantities of the required building blocks in a continuous process while maintaining their chemical, mechanical, and physical monodispersity contributes substantially to the suitability of this process. Furthermore, the size and shape of the produced microgels can be manipulated by various methods such as batch emulsions, microfluidics, lithography, electrodynamic spraying, or mechanical fragmentation, which determine the geometry of the building blocks and, thus, the 3D structure of the final scaffold1,10.
Recently, the concept of macroporous 3D scaffolds composed of functionalized microgel rods that rapidly interlink in aqueous solutions without further additives has been reported11. The anisotropy of microgel rods resulted in higher porosities and pore distributions with larger pore sizes compared to employing spherical microgels in this study11. In this way, less material creates larger pores with a variety of different pore geometries while maintaining the stability of the 3D scaffold. The system consists of two types of microgel rods with complementary primary amine and epoxy functional groups that are consumed within the interlinking reaction when coming in contact with each other. The functional groups that do not participate in the interlinking process remain active and can be used for selective post-modification with cell adhesive peptides or other bioactive factors. Fibroblast cells attach, spread, and proliferate when cultured inside the 3D scaffolds, first growing on the microgel surface and filling most of the macropores after 5 days. A preliminary co-culture study of human fibroblasts and human umbilical vein endothelial cells (HUVECs) showed promising results for the formation of vessel-like structures within the interlinked 3D scaffolds11.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>ABIL EM 90</td>
			<td>Evonik</td>
			<td>144243-53-8</td>
			<td>non-ionic surfactant</td>
		</tr>
		<tr>
			<td>2-Aminoethyl methacrylate hydrochloride</td>
			<td>TCI Chemicals</td>
			<td>A3413</td>
			<td>&#62;98.0%(T)(HPLC)</td>
		</tr>
		<tr>
			<td>8-Arm PEG-acrylate 20 kDa</td>
			<td>Biochempeg Scientific Inc.</td>
			<td>A88009-20K</td>
			<td>&#8805; 95 %</td>
		</tr>
		<tr>
			<td>AutoCAD 2019</td>
			<td>Autodesk</td>
			<td></td>
			<td>computer-aided design (CAD) software; modeling of microfluidic designs</td>
		</tr>
		<tr>
			<td>CHROMAFIL MV A-20/25 syringe filter</td>
			<td><s>CHROMAFIL</s>Carl Roth GmbH+Co.KG</td>
			<td>XH49.1</td>
			<td>pore size 0.20 &#181;m; Cellulose Mixed Esters (MV)</td>
		</tr>
		<tr>
			<td>Cover glass</td>
			<td>Marienfeld-Superior</td>
			<td></td>
			<td>type No. 1</td>
		</tr>
		<tr>
			<td>EMS Swiss line core sampling tool 0.75 mm</td>
			<td>Electron Microscopy Sciences</td>
			<td></td>
			<td>0.77 mm inner diameter, 1.07 mm outer diameter</td>
		</tr>
		<tr>
			<td>Ethanol absolut</td>
			<td>VWR Chemicals</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>FL3-U3-13Y3M 150 FPS series high-speed camera</td>
			<td>FLIR Systems</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Fluoresceinamine isomer I</td>
			<td>Sigma-Aldrich</td>
			<td>201626</td>
			<td></td>
		</tr>
		<tr>
			<td>Fluorescein isothiocyanate</td>
			<td>Thermo Fisher Scientific</td>
			<td>46424</td>
			<td></td>
		</tr>
		<tr>
			<td>25G x 5/8&#8217;&#8217; 0,50 x 16 mm needles</td>
			<td>BD Microlance 3</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Glycidyl methacrylate</td>
			<td>Sigma-Aldrich</td>
			<td>779342</td>
			<td>&#8805;97.0% (GC)</td>
		</tr>
		<tr>
			<td>GRGDS-PC</td>
			<td>CPC Scientific</td>
			<td>FIBN-015A</td>
			<td></td>
		</tr>
		<tr>
			<td>Hamilton 1000 Series Gastight syringes</td>
			<td>Thermo Fisher Scientific</td>
			<td>10772361/10500052</td>
			<td>PFTE Luer-Lock</td>
		</tr>
		<tr>
			<td>Hexane</td>
			<td>Sigma-Aldrich</td>
			<td>1,04,367</td>
			<td></td>
		</tr>
		<tr>
			<td>Lithium phenyl-2,4,6-trimethylbenzoylphosphinate</td>
			<td>Sigma-Aldrich</td>
			<td>900889</td>
			<td>&#8805;95 %</td>
		</tr>
		<tr>
			<td>Motic AE2000 trinocular microscope</td>
			<td>Ted Pella, Inc.</td>
			<td>22443-12</td>
			<td></td>
		</tr>
		<tr>
			<td>Novec 7100</td>
			<td>Sigma-Aldrich</td>
			<td>SHH0002</td>
			<td></td>
		</tr>
		<tr>
			<td>Oil Red O</td>
			<td>Sigma-Aldrich</td>
			<td>O9755</td>
			<td></td>
		</tr>
		<tr>
			<td>Paraffin</td>
			<td>VWR Chemicals</td>
			<td>24679320</td>
			<td></td>
		</tr>
		<tr>
			<td>Pavone Nanoindenter Platform</td>
			<td>Optics11Life</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate buffered saline</td>
			<td>Thermo Fisher Scientific</td>
			<td>AM9624</td>
			<td></td>
		</tr>
		<tr>
			<td>Polyethylene Tubing 0.38&#215;1.09mm medical grade</td>
			<td>dropletex</td>
			<td></td>
			<td>ID 0.38 mm OD 1.09 mm</td>
		</tr>
		<tr>
			<td>2-Propanol</td>
			<td>Sigma-Aldrich</td>
			<td>190764</td>
			<td>ACS reagent, &#8805;99.5%</td>
		</tr>
		<tr>
			<td>Protein LoBind Tubes</td>
			<td>Eppendorf</td>
			<td>30108132</td>
			<td></td>
		</tr>
		<tr>
			<td>Pump 11 Pico Plus Elite Programmable Syringe Pump</td>
			<td>Harvard Apparatus</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>RPMI 1640 medium</td>
			<td>Gibco</td>
			<td>11530586</td>
			<td></td>
		</tr>
		<tr>
			<td>SYLGARD 184 silicone elastomer kit</td>
			<td>Dow SYLGARD</td>
			<td>634165S</td>
			<td></td>
		</tr>
		<tr>
			<td>Trichloro-(1H,1H,2H,2H-perfluoroctyl)-silane</td>
			<td>Sigma-Aldrich</td>
			<td>448931</td>
			<td></td>
		</tr>
		<tr>
			<td>UVC LED sterilizing box</td>
			<td>UVLED Optical Technology Co., Ltd.</td>
			<td>9S SZH8-S2</td>
			<td></td>
		</tr>
	</tbody>
</table>

interlinked macroporous 3d scaffolds from microgel rods

A two-component system of functionalized microgels from microfluidics allows for fast interlinking into 3D macroporous constructs in aqueous solutions without further additives. Continuous photoinitiated on-chip gelation enables variation of the microgel aspect ratio, which determines the building block properties for the obtained constructs. Glycidyl methacrylate (GMA) or 2-aminoethyl methacrylate (AMA) monomers are copolymerized into the microgel network based on polyethylene glycol (PEG) star-polymers to achieve either epoxy or amine functionality. A focusing oil flow is introduced into the microfluidic outlet structure to ensure continuous collection of the functionalized microgel rods. Based on a recent publication, microgel rod-based constructs result in larger pores of several hundred micrometers and, at the same time, lead to overall higher scaffold stability in comparison to a spherical-based model. In this way, it is possible to produce higher-volume constructs with more free volume while reducing the amount of material required. The interlinked macroporous scaffolds can be picked up and transported without damage or disintegration. Amine and epoxy groups not involved in interlinking remain active and can be used independently for post-modification. This protocol describes an optimized method for the fabrication of microgel rods to form macroporous interlinked scaffolds that can be utilized for subsequent cell experiments.

<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/64010/64010fig02.jpg" /> 
Figure 2: Macroporous crosslinked scaffold structure. (A) 3D projection of a 500 &#181;m confocal microscopy Z-stack of the interlinked macroporous scaffold. Scale bar represents 500 &#181;m. (B) Interlinked scaffold composed of ~10,000 microgel rods on a cover glass taken directly out of water. Scale bar repre...

Watch this Scientific Journal Video about Interlinked Macroporous 3D Scaffolds from Microgel Rods at JoVE.com

Interlinked Macroporous 3D Scaffolds from Microgel Rods

Microgel rods with complementary reactive groups are produced via microfluidics with the ability to interlink in aqueous solution. The anisometric microgels jam and interlink into stable constructs with larger pores compared to spherical-based systems. Microgels modified with GRGDS-PC form macroporous 3D constructs that can be used for cell culture.

A two-component system of functionalized microgels from microfluidics allows for fast interlinking into 3D macroporous constructs in aqueous solutions ...

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