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Biomaterials

Biomaterials - Poster Session E

Poster O11 - Novel Dynamic Controlled-Release Media Shower Bioreactor Design for 3D Bioprinted Nipple-Areola Complexes (NACs)

Saturday, October 26, 2024
10:00 AM – 11:00 AM EST
Location: Exhibit Hall E, F & G

Introduction:  Breast cancer -- the second most common cancer worldwide, and the most commonly diagnosed cancer among U.S. women -- currently has no cure, and treatments become incredibly invasive as the disease progresses. Breast cancer nipple-excision mastectomies are particularly invasive, as patients no longer retain their nipple-areola complexes (NACs), thus losing the primary function of their breasts (lactation). A life-saving yet dehumanizing procedure, patients are left bodily and mentally dysmorphic. Current NAC reconstruction and nipple graft research often compromises vascularization capacity and visual native "aesthetic" in exchange for reducing the risk of immune rejection. 3D bioprinted NAC constructs, on the other hand, balance all three aspects at once by 3D-modeling the NACs to retain native appearance, 3D-designing internal vasculature, and bioprinting the designs using porous hydrogel biomaterials like gelatin methacrylate to seed cells otherwise found in/around native NACs to facilitate immune functionality. These cells, namely dermal fibroblasts and keratinocytes, have specific culture environment requirements for survival within said hydrogels, for which there is currently no research nor standard design for 3D bioprinted NACs. This design is the first dynamic controlled-release media shower bioreactor specifically tailored for culturing multiple 3D bioprinted NACs at a time, only requiring an external peristaltic pump. Computational fluid dynamics (CFD) models and bench-top testing show that this design retains a closed-loop, evenly circulated controlled release of fluid, with a high pressure input for precise outflow, for multiple days straight. Thus, this bioreactor design shows great promise for the future of breast cancer research and nipple-excision mastectomy patients.

Materials and

Methods:  The bioreactor was designed via 3D modeling software SolidWorks, of which the Computational Fluid Dynamics (CFD) toolbox was employed to develop CFD models with only 2 manually calculated parameters (inlet volume flow rate and inlet velocity) and standard environmental pressure. All prototypes were 3D printed via the Envision-One DLP printer and Envisiontec MedClear Resin for biocompatibility. For bench-top testing, a Cole-Parmer Masterflex L/S peristaltic pump was used to transfer fluid at 20 mL/min through a 2-way tubing system, where one end of the 2-way tube was connected to the inlet port of the bioreactor via rubber hose and adapter, and the other end was connected to the media source (for bench-top purposes, 45 mL diH2O with food coloring in 3 50 mL Falcon conical tubes with 2-way tubing rubber stoppers). The outlet port of the bioreactor was also connected to the media source via rubber hose and adapter, thus fostering a closed-loop system. To ensure that the loop was closed (i.e. no leaking, breaking, or escape of fluid from the bioreactor setup), the apparatus was monitored for 72 hours with daily weigh-ins of the fluid remaining in the Falcon media tubes. These media tubes were weighed on a lab scale at hour "0" to capture their initial weights, and then weighed once every 24 hours by draining as much fluid as possible from the bioreactor chambers back into the tubes, followed by reconnecting the tubing back into place with the outlet ports, and repeating the process until the 72-hour mark.

Results, Conclusions, and Discussions: The results of the Computational Fluid Dynamics (CFD) models computed a total of 17,295 fluid cells of which 11,228 contacted solids, suggesting that the fluid flows dynamically congruent to the solid body design. Flow trajectories of the CFD models reveal a high pressure input of ~101596.64 Pa within the upper chamber of the bioreactor directly connected to the inlet port, suggesting that media comes into the bioreactor developing a high pressure environment to be alleviated immediately by filleted shower holes that decrease the pressure down to ~101410.24 Pa. The lower portion of the bioreactor -- where the NACs are placed -- retains a steady, even fluid circulation of ~101317.04 Pa, suggesting that NACs will receive a controlled-release of the media in the form of a shower (note: pressure differences seem "small" given the small dimensions of both the bioreactor and 3D bioprinted NACs). Bench-top testing results further corroborated the CFD models, having tested 3 standalone bioreactors simultaneously, and having tested 1 "chambered case" with 3 chambers consisting of the individual bioreactors alongside a standalone bioreactor. The 3 separate bioreactor test retained an average difference in weight as 4.35 g (an insignificant loss attributed to fluid stuck in the 2-way tubing system after draining, given that no fluid leaks or breaks in the bioreactor design occurred). The chambered case test revealed that the average difference in weight between the 3 bioreactor chambers was 3.86 g, and no spillage/leakage between the chambers was observed (given that all the media colors remained true to their dye, and that no fluid leaks from the case itself were present), and ran for 72 hours as did the standalone bioreactor, which observed a 2.98 g difference in weight. While the next steps of this design include testing 3D bioprinted NACs seeded with the intended cells, these experiments revealed that this bioreactor design facilitates volume inflow, outflow, and internal even circulation, can run for multiple days on end, and does not leak/spill any media, suggesting that this novel design is ready for the future of 3D bioprinted NACs research.

Acknowledgements (Optional):  Amal Shabazz, Ph.D. Student at the Tissue Engineering & Biomaterials Laboratory (TEBL) of the Fischell Department of Bioengineering, whose 3D bioprinted NACs project was the main purpose and application of this design and provided guidance and support throughout prototype iterating, testing, and modeling; and Dr. John Fisher, TEBL PI, for the support and guidance of this project.