The Design of Printed Hybrid Constructs to Serve as Cartilage Templates for Bone Repair
Friday, May 5, 2017
9:00 AM-11:00 AM
BIOMED Master's Thesis Defense
Title:
The Design of Printed Hybrid Constructs to Serve as Cartilage Templates for Bone Repair
Speaker:
Nathan Tessema Ersumo, MS Candidate, School of Biomedical Engineering, Science and Health Systems
Advisor:
Kara Spiller, PhD, Assistant Professor, School of Biomedical Engineering, Science and Health Systems
Abstract:
With an estimated annual incidence of over 2.2 million cases across the world, critical size bone defects pose an unmet challenge requiring improved therapeutic strategies. Current clinical solutions, namely autologous and allogeneic grafts, are associated with a number of complications which include supply shortage, donor site morbidity and immune rejection. Given the poor vascularization observed with bioresorbable bone template scaffolds, some have turned to engineering the endogenous repair pathway by developing implantable cartilage templates susceptible to the bone transformation process known as endochondral ossification seen in native defects. Yet considerations relating to the implants’ mechanical behavior, porosity and swelling, all of which are crucial to mimicking the endochondral ossification process, remain largely unaddressed in past studies.
Through a parameter-driven preliminary study, we have devised a method to improve spatial resolution and property modulation by incorporating additive manufacturing into the fabrication process of cartilage templates destined for ossification-mediated defect repair. Based on our findings that hydrogel extrusion introduces structural discontinuities leading to excessive swelling and time-dependent mechanical deformation, we advance a biofabrication method involving (1) the 3D printing of a porous hybrid construct comprised of a stiff polycaprolactone network interwoven with sacrificial poly(ethylene glycol) material, (2) the casting of a cell-laden hydrogel material into the primary porous network, and (3) the evacuation of the sacrificial poly(ethylene glycol) material to create a secondary porous network. The architecture of the generated templates was modulated by varying the widths of the secondary pores and hydrogel struts. Generated templates were subjected to geometric analysis by photography, porosity evaluation by micro-computed tomography, stress relaxation testing and a swelling study. The incorporation of a stiff network constrained swelling by more than half, while decreased porosity-to-hydrogel content ratios mitigated time-dependent deformation.
Contact Information
Ken Barbee
215-895-1335
barbee@drexel.edu