This project was partially funded by a grant from the Pediatric Orthopaedic Society of North America (POSNA) and the National Institutes of Health grant NIBIB R21EB025378-01 (Exploratory Bioengineering Research Grant).

1. Obtaining and Preprocessing Microspheres
<ol>
	<li>Produce microspheres with the desired matrix encapsulated (PLA-DM)2. 
	NOTE: It is imperative that the microspheres are of uniform size. For this reason, sieving the microspheres prior to use is essential. Although matrix decellularization and encapsulation have been detailed in previous publications2, a brief summary of the process follows.
	<ol>
		<li>First, harvest cartilage plugs from porcine hind limbs. Decel...

<ol>
	<li>Hutchmaker, D., Teoh, S., Zein, I., Ng, K. W., Schantz, J. -. T., Leahy, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Design+and+Fabrication+of+a+3D+Scaffold+for+Tissue+Engineering+Bone.">Design and Fabrication of a 3D Scaffold for Tissue Engineering Bone.</a> Synthetic Bioabsorbable Polymers and Implants. 15 (2), 845-847 (1988).</li><li>Ghosh, P., Gruber, S. M. S., Lin, C. -. Y., Whitlock, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microspheres+containing+decellularized+cartilage+induce+chondrogenesis+and+remain+functional+after+incorporation+within+a+poly(caprolactone)+filament+useful+for+fabricating+a+3D+scaffold.">Microspheres containing decellularized cartilage induce chondrogenesis and remain functional after incorporation within a poly(caprolactone) filament useful for fabricating a 3D scaffold.</a> Biofabrication. , (2018).</li><li>Partington, L., 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=Biochemical+changes+caused+by+decellularization+may+compromise+mechanical+integrity+of+tracheal+scaffolds.">Biochemical changes caused by decellularization may compromise mechanical integrity of tracheal scaffolds.</a> Acta Biomaterialia. 9 (2), 5251-5261 (2013).</li><li>Hutmacher, D. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Scaffolds+in+tissue+engineering+bone+and+cartilage.">Scaffolds in tissue engineering bone and cartilage.</a> Biomaterials. 21 (24), 2529-2543 (2000).</li><li>Kang, H., Hollister, S. J., La Marca, F., Park, P., Lin, C. -. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Porous+biodegradable+lumbar+interbody+fusion+cage+design+and+fabrication+using+integrated+global-local+topology+optimization+with+laser+sintering.">Porous biodegradable lumbar interbody fusion cage design and fabrication using integrated global-local topology optimization with laser sintering.</a> Journal of biomechanical engineering. 135 (10), 101013-101018 (2013).</li><li>Kang, H., Lin, C. Y., Hollister, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Topology+optimization+of+three+dimensional+tissue+engineering+scaffold+architectures+for+prescribed+bulk+modulus+and+diffusivity.">Topology optimization of three dimensional tissue engineering scaffold architectures for prescribed bulk modulus and diffusivity.</a> Structural and Multidisciplinary Optimization. 42 (4), 633-644 (2010).</li><li>Lin, C. -. Y., 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=Functional+bone+engineering+using+ex+vivo.+gene+therapy+and+topology-optimized,+biodegradable+polymer+composite+scaffolds.">Functional bone engineering using ex vivo. gene therapy and topology-optimized, biodegradable polymer composite scaffolds.</a> Tissue Engineering. 11 (9-10), 1589-1598 (2005).</li><li>Lin, C. -. Y., Hsiao, C. -. C., Chen, P. -. Q., Hollister, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interbody+Fusion+Cage+Design+Using+Integrated+Global+Layout+and+Local+Microstructure+Topology+Optimization.">Interbody Fusion Cage Design Using Integrated Global Layout and Local Microstructure Topology Optimization.</a> Spine. 29 (16), 1747-1754 (2004).</li><li>Zopf, D., Hollister, S., Nelson, M., Ohye, R., Green, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bioresorbable+Airway+Splint+Created+with+a+Three-Dimensional+Printer.">Bioresorbable Airway Splint Created with a Three-Dimensional Printer.</a> New England Journal of Medicine. 368 (21), 2043-2045 (2013).</li><li>Pati, F., Song, T. H., Rijal, G., Jang, J., Kim, S. W., Cho, D. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ornamenting+3D+printed+scaffolds+with+cell-laid+extracellular+matrix+for+bone+tissue+regeneration.">Ornamenting 3D printed scaffolds with cell-laid extracellular matrix for bone tissue regeneration.</a> Biomaterials. 37, 230-241 (2015).</li><li>Zhang, W., 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=The+effect+of+interface+microstructure+on+interfacial+shear+strength+for+osteochondral+scaffolds+based+on+biomimetic+design+and+3D+printing.">The effect of interface microstructure on interfacial shear strength for osteochondral scaffolds based on biomimetic design and 3D printing.</a> Materials Science and Engineering C. 46, 10-15 (2015).</li><li>Williams, J. M., 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=tissue+engineering+using+polycaprolactone+scaffolds+fabricated+via.+selective+laser+sintering.">tissue engineering using polycaprolactone scaffolds fabricated via. selective laser sintering.</a> Biomaterials. 26 (23), 4817-4827 (2005).</li><li>Monibi, F. A., Cook, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tissue-Derived+Extracellular+Matrix+Bioscaffolds:+Emerging+Applications+in+Cartilage+and+Meniscus+Repair.">Tissue-Derived Extracellular Matrix Bioscaffolds: Emerging Applications in Cartilage and Meniscus Repair.</a> Tissue Engineering Part B: Reviews. , (2017).</li><li>Wiles, K., Fishman, J., Coppi, P., Birchall, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Host+Immune+Response+to+Tissue-Engineered+Organs:+Current+Problems+and+Future+Directions.">The Host Immune Response to Tissue-Engineered Organs: Current Problems and Future Directions.</a> Tissue Engineering Part B: Reviews. 22 (3), (2016).</li><li>Sutherland, A. J., Detamore, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bioactive+Microsphere-Based+Scaffolds+Containing+Decellularized+Cartilage.">Bioactive Microsphere-Based Scaffolds Containing Decellularized Cartilage.</a> Macromolecular Bioscience. , (2015).</li><li>Whitlock, P. W., Smith, T. L., Poehling, G. G., Shilt, J. S., Van Dyke, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+naturally+derived,+cytocompatible,+and+architecturally+optimized+scaffold+for+tendon+and+ligament+regeneration.">A naturally derived, cytocompatible, and architecturally optimized scaffold for tendon and ligament regeneration.</a> Biomaterials. , (2007).</li><li>Whitlock, P. W., 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+cyclic+strain+on+tensile+properties+of+a+naturally+derived,+decellularized+tendon+scaffold+seeded+with+allogeneic+tenocytes+and+associated+messenger+RNA+expression.">Effect of cyclic strain on tensile properties of a naturally derived, decellularized tendon scaffold seeded with allogeneic tenocytes and associated messenger RNA expression.</a> Journal of surgical orthopaedic advances. 22 (3), 224-232 (2013).</li><li>Whitlock, P. W., 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=A+novel+process+for+optimizing+musculoskeletal+allograft+tissue+to+improve+safety,+ultrastructural+properties,+and+cell+infiltration.">A novel process for optimizing musculoskeletal allograft tissue to improve safety, ultrastructural properties, and cell infiltration.</a> Journal of Bone and Joint Surgery - Series A. 94 (16), 1458-1467 (2012).</li><li>Schultz, G. S., Davidson, J. M., Kirsner, R. S., Herman, I. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamic+Reciprocity+in+the+Wound+Microenvironment.">Dynamic Reciprocity in the Wound Microenvironment.</a> Wound Repair Regeneration. 19 (2), 134-148 (2012).</li><li>Benders, K. E. M., van Weeren, P. R., Badylak, S. F., Saris, D. B. F., Dhert, W. J. A., Malda, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extracellular+matrix+scaffolds+for+cartilage+and+bone+regeneration.">Extracellular matrix scaffolds for cartilage and bone regeneration.</a> Trends in Biotechnology. 31 (3), 169-176 (2013).</li><li>Crapo, P., Gilbert, T., Badylak, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+overview+of+tissue+and+whole+organ+decellularization+processes.">An overview of tissue and whole organ decellularization processes.</a> Biomaterials. 32 (12), 3233-3243 (2011).</li><li>Guan, Y., 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=Porcine+kidneys+as+a+source+of+ECM+scaffold+for+kidney+regeneration.">Porcine kidneys as a source of ECM scaffold for kidney regeneration.</a> Materials Science and Engineering C. 56, 451-456 (2015).</li><li>Dean, R. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Kinetic+studies+with+alkaline+phosphatase+in+the+presence+and+absence+of+inhibitors+and+divalent+cations.">Kinetic studies with alkaline phosphatase in the presence and absence of inhibitors and divalent cations.</a> Biochemistry and Molecular Biology Education. 30 (6), 401-407 (2002).</li></ol>

The authors have nothing to disclose.

Both decellularized matrices and 3D printed PCL scaffolds have independently been shown to allow adhesion and proliferation of cells, validating their use for osteochondral repair10,11,12. The use of decellularized matrix in engineering approaches to tissue repair has been a subject of much interest and success in the recent past2,3,14<...

Current tissue engineering techniques for clinical applications such as bone, cartilage, tendon, and ligament reconstruction use auto- and allografts to repair damaged tissue. Each of these techniques is performed routinely as a &#34;gold standard&#34; in clinical practice by first harvesting the donor tissue either from the patient or a cadaveric match, and then placing the donor tissue into the defect site2. However, these strategies are limited by donor site morbidity, donor site scarcity for large defects, risk of infection, and difficulty finding grafts that match the desired geometry. In addition, studies have shown that allografts used for reconstruction have reduced mechanical and biologic properties when compared with native tissue3. With these considerations in mind, tissue engineers have recently turned to three dimensional (3D) bioprinting to produce custom, complex geometries that are biologically active and designed to accommodate defect size and shape while providing sufficient mechanical properties until biologic remodeling is complete.
Ideally, a 3D-printed scaffold would consist of a polymeric backbone that can retain the required mechanical stability of native tissue while the incorporated biologics offer biochemical cues to surrounding cells, leading to their migration, proliferation, differentiation, and tissue production2,5. Unfortunately, most constructs that contain biologic components are made with gels or polymers that are too weak to withstand in vivo forces experienced by the targeted tissues for auto/allograft reconstruction. Other polymers such as polylactic acid (PLA) are bioresorbable, 3D printable and structurally sound, but are printed at temperatures at or above 210 &#176;C - making it impossible for biologics to be co-printed during fabrication. Polycaprolactone (PCL) is another FDA-cleared, bioresorbable polymer that can be 3D printed at a lower temperature (65 &#176;C), which has become increasingly popular in fabricating patient-specific implants with complex morphologies5,6,7,8,9. However, most bioprinters using pneumatic technology make it impossible to print PCL at lower temperatures where biological activities can remain unharmed. To date, the integration of these polymers with auto/allografts into a novel printable biomaterial has yet to be accomplished. In the absence of such a material, a true tissue engineered approach to tissue reconstruction is unlikely. Therefore, we have sought to combine PLA, PCL, and decellularized allograft matrices (DM) to utilize the advantages of each material in order to manufacture a viable construct capable of reconstructing complex tissues. This process would provide the initial mechanical strength necessary to resist in vivo forces and the thermal stability to accommodate additive manufacturing in a construct that induces formation of the desired tissue.
In a recent attempt to address the aforementioned hurdles, we showed that it is feasible to encapsulate decellularized cartilage extracellular matrix within a thermally protective PLA barrier that can be extruded within PCL filaments, maintaining the ability of DM to influence surrounding host cells2. This has inspired us to seek clinically effective approaches for tissue reconstruction. In the current study, we utilize the platform technology to build all-in-one scaffolds that include PLA, DM, and PCL (PLA-DM/PCL).
Our goal is to improve the efficacy and utility of allografts using the proposed novel biofabrication technique to more accurately recapitulate native tissue, to ultimately use them in various applications.

<table border="0" cellpadding="0" cellspacing="0" style="width:877px;" width="877">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Sieve machine</td>
			<td style="width:396px;">Haver &#38; Boecker Tyler</td>
			<td style="width:132px;">Ro-Tap RX 29-E Pure</td>
			<td style="width:155px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sieve 90 um</td>
			<td>Fisherbrand</td>
			<td>170328156</td>
			<td>No. 170</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sieve 53 um</td>
			<td>Fisherbrand</td>
			<td>162513588</td>
			<td>No. 270</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sieve 106 um</td>
			<td>Fisherbrand</td>
			<td>162018121</td>
			<td>No. 140</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sputter coater</td>
			<td>Leica</td>
			<td>n/a</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Scanning Electron Microscope</td>
			<td>Hitachi, USA</td>
			<td>n/a</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Filabot EX2</td>
			<td>Filabot.com</td>
			<td>FB00061</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Filabot Spooler</td>
			<td>Filabot.com</td>
			<td>FB00073</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">CAPA 6506</td>
			<td>Perstorp</td>
			<td>24980-41-4</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Phosphate buffered saline, PBS</td>
			<td>Gibco</td>
			<td>10010023</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">6&#34; Fan</td>
			<td>Comfort Zone, Amazon</td>
			<td>n/a</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Ultrasonic Water Bath</td>
			<td>Cole Parmer</td>
			<td>SK-08895-13</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Dreamer</td>
			<td>FlashForge</td>
			<td>n/a</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Drum Mixer</td>
			<td>Custom made</td>
			<td>n/a</td>
			<td>Similar piece of equipment: https://www.coleparmer.com/i/argos-technologies-flexiroll-digital-tube-roller-shaker-120-vac/0439744?PubID=UX&#38;persist=true&#38;ip= 
			no&#38;gclid=CjwKCAjw- 
			dXaBRAEEiwAbwCi5khGDMz0 
			dTjsraEsBGfhMEH7ytx 
			LQWGUPNgUJYQ1p3vj_yxkYoI_ 
			ixoC9GwQAvD_BwE</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Micro Balance</td>
			<td>Mettler Toledo, Fisher Scientific</td>
			<td>01-913-851</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Simplify3D</td>
			<td>Simplify3D</td>
			<td>n/a</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">SolidWorks</td>
			<td>SolidWorks</td>
			<td>n/a</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Microspheres</td>
			<td>Produced in-house, see concurrently submitted JoVE submission</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">p-nitrophenyl phosphate, disodium salt, hexahydrate</td>
			<td>Millipore</td>
			<td>4876-5GM</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Phosphatase, alkaline</td>
			<td>Roche Diagnostics GmbH</td>
			<td>10 713 023 001</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Absorbance Reader</td>
			<td>Tecan</td>
			<td>Sunrise</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Tris-HCl Buffer</td>
			<td>Sigma-Aldrich</td>
			<td>T6455-100ML</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Heated shaker</td>
			<td>New Brunswick Scientific</td>
			<td>Excella E24</td>
			<td></td>
		</tr>
	</tbody>
</table>

novel process for 3d printing decellularized matrices

3D bioprinting aims to create custom scaffolds that are biologically active and accommodate the desired size and geometry. A thermoplastic backbone can provide mechanical stability similar to native tissue while biologic agents offer compositional cues to progenitor cells, leading to their migration, proliferation, and differentiation to reconstitute the original tissues/organs1,2. Unfortunately, many 3D printing compatible, bioresorbable polymers (such as polylactic acid, PLA) are printed at temperatures of 210 &#176;C or higher - temperatures that are detrimental to biologics. On the other hand, polycaprolactone (PCL), a different type of polyester, is a bioresorbable, 3D printable material that has a gentler printing temperature of 65 &#176;C. Therefore, it was hypothesized that decellularized extracellular matrix (DM) contained within a thermally protective PLA barrier could be printed within PCL filament and remain in its functional conformation. In this work, osteochondral repair was the application for which the hypothesis was tested. As such, porcine cartilage was decellularized and encapsulated in polylactic acid (PLA) microspheres which were then extruded with polycaprolactone (PCL) into filament to produce 3D constructs via fused deposition modeling. The constructs with or without the microspheres (PLA-DM/PCL and PCL(-), respectively) were evaluated for differences in surface features.

After sieving, microspheres should appear uniform and be free from aggregates. Under SEM, the sieved microspheres may have small pores on their surface, but will otherwise be spherical and smooth, as shown in Figure 1. All extruded filaments should be of uniform diameter and circular cross-section. A filament that contains microspheres (PLA-DM/PCL) will have a slightly more matte finish while a PCL-only (PCL(-)) filament would look more glossy. The PLA-DM/PCL...

Watch this Scientific Journal Video about Novel Process for 3D Printing Decellularized Matrices at JoVE.com

Novel Process for 3D Printing Decellularized Matrices

This protocol describes the production of polycaprolactone (PCL) filament with embedded polylactic acid (PLA) microspheres which contain decellularized matrices (DM) for 3D printing of structural tissue engineering constructs.

3D bioprinting aims to create custom scaffolds that are biologically active and accommodate the desired size and geometry. A thermoplastic backbone can ...

This method allows co-printing of both structural synthetics and biologic components for tissue-engineered scaffolds. These scaffolds can replicate the native tissue environment more accurately, which can be beneficial for cultured cells. The main advantage of this technique is that it can print mechanically sound structures without damaging the biologic material encapsulated within the scaffolds in an all-in-one technique for tissue engineering.Produce microspheres with the desired matrix encapsulated. These microspheres were made with decellularized cartilage from porcine hind limbs. They vary in size.Work with a sieve machine to obtain microspheres of uniformed size. Ensure the three sieve trays have been thoroughly cleaned and dried prior to use. Assemble the sieve shaker with the larger mesh tray on top and the smaller mesh tray in the middle.Put the sieve pan on the bottom. Place dry microspheres in the top-most tray. Then place the lid on the tray.Coarse sieve for eight to ten minutes. Then fine sieve for eight to ten minutes. While waiting, arrange weigh paper for the sieved spheres.When sieving is complete, carefully remove a sieve tray. Place the tray upside down on the weigh paper. Gently tap the sides to ensure most of the spheres fall out.With all of the sieve plates emptied onto weigh paper, discard the oversized and undersized spheres. The remaining spheres have the correct size for use in subsequent steps. Place these spheres into a labeled centrifuge tube.Store the tube in a 20 degree Celsius freezer until needed. Weigh the material necessary to make the filament material. Make a one-to-four weight ratio of microspheres to polycaprolactone powder with at least 25 grams of microspheres.Transfer the powder mixture to a miniature rolling mixer. Mix the powder at 20 rotations per minute for five minutes. After five minutes, stop the rotation and flip the container.Then mix at 20 rpm for an additional five minutes. To continue, take the mixture to an extruder and spooler setup. Setup the extruder so its outlet is about 60 centimeters from the inlet of a spooler.Then at the extruder heating element, be sure there is no insulating jacket. Place a desktop fan about halfway between the extruder and spooler to cool the extrudate. Put another fan near the heating jacket to cool it with ambient air.Next ensure the proper nozzle is attached to the extruder and set the heating element temperature. Start the cooling fans and allow the instrument to reach a steady state. After 20 to 30 minutes, get the microsphere PCL mixture and fill the extruder hopper.Turn on the spooler and the extruder auger to initiate filament extrusion. Use forceps and manually pull the initial extruded filament. Feed the filament to the filament spooler.As it is extruded, observe the filament to identify its composition. After some time, the filament composition will appear uniform which is desired. Wrap tape around the filament to mark the start of the uniform region.Beyond the spooler rollers, monitor the diameter of the filament. Use calipers to test if the diameter is close to the desired 1.75 mm. Adjust the spooler and extruder speeds and temperatures as necessary.To adjust adjust the filament diameter, first alter the spooler and extruder speeds. You may also change the extruder temperature, although this is usually not necessary. Continue refilling the hopper and extruding until all of powder is used.When the hopper is almost empty, add PCL powder to the hopper to flush out the microsphere mixture. Monitor the extrudate while adding the PCL powder. At first, microspheres will still be visible in the extrudate.Eventually when no more microspheres are visible, stop adding the PCL. Separate and label the filament with microspheres in the desired concentration. When there is minimal powder in the hopper, stop extruding and turn off the equipment.The filament can be used in a standard fused deposition modeling printer. Load the filament into the printer that is fitted with nozzles of the desired diameter. With the model loaded, set the temperature and linear speed for the printing and begin depositing the filament.The custom filament is deposited layer by layer. Pay special attention to the first layer and adjust settings as needed. These two 3D printed scaffolds are difficult to distinguish at this scale.One has filament containing polycapralactone, PCL only. The other has PCL filament with embedded microspheres of polylactic acid and decelluarized matrices. Viewed using scanning electron microscopy, the PCL-only scaffold appears mostly smooth.By contrast, for the other filament, microspheres embedded in the PCL are visible throughout the sample. While attempting this procedure, it is important to remember that over or undersized microspheres can impact the flow dynamics of the material in the extruder. For this reason, be sure to properly prepare your microspheres prior to use.In order to minimize waste, it is advisable to create one large batch of filament required for all experiments rather than to create smaller batches more frequently. Expertise in filament production will come over time. Scaffolds produced following this procedure can be further assessed in vitro and in vivo to answer additional questions about enhanced induction and mechanical strength compared to other bio-printed scaffolds.After its development, this technique paved the way for researchers in the field of tissue engineering to explore contragenic induction of decelluarized porcine matrix within the 3D scaffolds. Don't forget that working with small particulates can present respiratory hazards. Wearing a small particulate mask during this procedure is encouraged.

novel-process-for-3d-printing-decellularized-matrices

Research

JoVE Journal

Bioengineering

7.0K vues.  University of Cincinnati. Cette méthode permet la co-impression de synthétiques structurels et de composants biologiques pour les échafaudages d’ingénierie tissulaire. Ces échafaudages peuvent reproduire l’environnement tissulaire indigène avec plus de précision, ce qui peut être bénéfique pour les cellules de culture. Le principal avantage de cette technique est qu’elle peut imprimer mécaniquement des structures sonores sans endommager le matériau biologique encapsulé dans les échafaudages dans un...