Fast-printed porous scaffolds with micron level resolution for pro-regenerative implants

Introduction:: 3D printing has a high potential for developing biomedical devices, especially porous scaffolds. Stereolithography (SLA) 3D printing systems are commonly used to print high-resolution structures. Previous work from our group has demonstrated that 25-45μm interconnected, spherical pores are pro-healing when implanted in many tissues[1] and we are exploring ways to 3D-print such structures. Comparing 3D printing methods, many of the fabrication techniques have a resolution of 50–200μm. However, commercially available SLA 3D printers can build objects at an accuracy of 20μm or lower, and in the Z direction the layer thickness can reach a resolution at 50μm. But excessive polymerization (over-curing) is an obstacle in maintaining control of layer thickness and a challenge for porous scaffolds. To get a stabilized printing environment with precisely controlled layer thickness, a new printing methodology is needed. The KLOE high-resolution 3D lithographic laser system (KLOE, 2-4 rue des Arbousiers, 34270 Saint-Mathieu-de-Tréviers, France) is used here to perform the experiments.

Materials and Methods:: A commercial 3D printing resin, DS2000 (DWS, Via Della Meccanica, 21 36016 Theine (VI) Italy), was used to fabricate all designs and tests. Sylgard-184 silicone elastomer kit (Dow, 2211 H.H. Dow Way, Midland, MI) was used to fabricate the Polydimethylsiloxane (PDMS). To create a stable printing environment, the PDMS layer on the printer platen in the monomer vat was immersed in 40mL DS2000 for 120 hours, the resin was then removed, and the PDMS was soaked in 70% ethanol for 30 minutes, then rinsed with 70% ethanol until clean. The PDMS surface was then placed inside a UV source (Spectrolinker XL-1500 UV Crosslinker, 4 Dubon Court, Farmingdale, NY) with 365nm UV lights (BLE-1T151) for 9 minutes. The above steps were repeated until a stable result was obtained as measured by a sensitivity test.

Results, Conclusions, and Discussions:: Two types of contamination were observed on the vat PDMS coating during the printing process, internal (bulk) contamination, and surface contamination. These have significant effects on the printing quality. After the PDMS was immersed in the photo-curable liquid for 240 hours and exposed to UV light for 18 minutes, the internal contamination can be controlled. With the desired pair of printing velocity and laser intensity, a porous scaffold with the micron-level resolution was printed precisely within 3 hours without surface contamination, showing the capability of rapid prototyping with SLA 3D printing in a stabilized environment. Several complex structures were fabricated and demonstrated the ability to manufacture porous scaffolds with 40μm interconnected, cubical pores in a stable manner. Implantation experiments to access the foreign body reaction will begin soon.

Acknowledgements (Optional): : Funding for this project comes from the Center for Dialysis Innovation (CDI) and the Northwest Kidney Centers.

References (Optional): : [1] Madden, L. R.; Mortisen, D. J.; Sussman, E. M.; Dupras, S. K.; Fugate, J. A.; Cuy, J. L.; Hauch, K. D.; Laflamme, M. A.; Murry, C. E.; Ratner, B. D. Proangiogenic scaffolds as functional templates for cardiac tissue engineering. Proc Natl Acad Sci USA 2010, 107 (34), 15211-15216.