MS Candidate Christina Merrill - "Porous HA-PEEK Composite Scaffolds as a Delivery Device for rhBMP-2 and Cell Culture Substrate"
|Start:||4/10/2013 at 10:00AM|
|End:||4/10/2013 at 12:00PM|
|Location:||103 Multidisciplinary Research Building|
Spinal fusion is a surgical procedure in which two vertebrae are fused to alleviate pain from disc degeneration or other spinal pathologies. Interbody spinal fusion cages are used to restore vertebral height and provide mechanical support. To induce fusion of the vertebrae, polyetheretherketone (PEEK) cages are filled with bone autograft or a porous collagen sponge containing recombinant human bone morphogenetic protein-2 (rhBMP-2). Autograft is limited by supply, risk of increased morbidity and pain at the donor site. The use of rhBMP-2 in a collagen sponge is limited by supraphysiological doses and burst release leading to a risk of hematomas, bone resorption, and ectopic bone formation. Porous and bioactive PEEK cages are proposed as a means to improve the delivery of or obviate the need for rhBMP-2. Hydroxyapatite (HA) is added to these cages to provide bioactivity and a substrate for surface adsorption of rhBMP-2. Therefore HA-PEEK scaffolds were hypothesized to retain more rhBMP-2 than PEEK alone, resulting in a more sustained release of a given dose. rhBMP-2 was adsorbed onto porous HA-PEEK and PEEK scaffolds, and the release of rhBMP-2 from the scaffold was measured. Surprisingly, both PEEK and HA-PEEK adsorbed and gradually released similar levels of rhBMP-2 over a 14-day period. The porosity of HA-PEEK scaffolds is proposed to allow for cell infiltration and bone ingrowth. The use of an ellipsoidal salt porogen was previously shown to improve permeability compared to conventional cubic salt crystals in the same size range. Therefore, HA-PEEK scaffolds prepared with an ellipsoidal porogen were hypothesized to facilitate greater infiltration of primary osteoblasts than HA-PEEK scaffolds prepared with a cubic porogen. It was also hypothesized that osteoblasts cultured on HA-PEEK scaffolds would exhibit better cell spreading and morphology than osteoblasts cultured on PEEK scaffolds. Results of this study were inconclusive (pending histological characterization) due to an initial seeding density which may have been too low for effective proliferation of cells throughout the scaffolds.