Event Abstract Back to Event Surface adsorbed vitronectin linked to differences in macrophage activity on polycarbonate and polyester surfaces Moira C. Vyner1* and Brian G. Amsden1* 1 Queen's University, Department of Chemical Engineering, Canada Introduction: In vivo, polycarbonates degrade via macrophage mediated surface erosion, whereas polyesters degrade primarily via bulk hydrolysis. The reason for this difference in degradation mechanism is unclear and may be due to a difference in macrophage response to the surfaces. Macrophage response to a material is believed to be influenced by the proteins that adsorb to the biomaterial surface, primarily complement and immunoglobulin proteins. We hypothesized that the difference in degradation of these polymers is due to differences in macrophage activity, driven by the composition of the protein layers adsorbed to the polymer surfaces. In this study, 100 kg/mol poly(trimethylene carbonate) (PTMC), which degrades by macrophage mediated erosion, and an elastomer formed from 5000 g/mol acrylated star poly(D,L lactide-co-e-caprolactone) (ELAS), which resists macrophage mediated erosion, were used as model surfaces to measure macrophage activity, and identify and relatively quantify proteins that adsorb to the polymer surfaces. Methods: PTMC[1] and ELAS[2] were fabricated as previously described. To determine differences in macrophage attachment or activity, RAW 264.7 macrophages were cultured on PTMC and ELAS surfaces in DMEM (10% adult bovine plasma). Macrophage number and production of reactive oxygen species (ROS), superoxide anion, and esterase were measured on days 1, 3, 7, 10 and 14. To increase the surface area available for protein adsorption, PTMC and ELAS were formed into microspheres. The microspheres were incubated in DMEM (10% adult plasma) for 12 hours and adsorbed proteins were eluted with 1% SDS. The identities and relative quantities of proteins on each surface were determined by reductive methylation followed by LC-MS/MS. Relative quantity is given as the ratio of the quantity of protein found on the ELAS:PTMC surfaces. Results and Discussion: Macrophages grown on the ELAS surface decreased in number after day 3, and preferentially produced ROS over esterase (Fig. 1), though ELAS is not eroded by oxidative species, suggesting that polyesters degrade less readily by macrophage mediated mechanisms both due to a lower number of macrophages and the type of degradative species the macrophages secrete. No differences in immunoglobulin or complement adsorption were measured between the polymer surfaces (Fig. 2). Vitronectin adsorbed in significantly higher amounts to the ELAS surface. Surface adsorbed vitronectin has been associated with increased foreign body giant cell formation in macrophages activated by IL-4, though no studies have measured macrophage activation by adsorbed vitronectin alone. Conclusion: These results suggest that the reason for the difference in degradation mechanism of polycarbonates compared to polyesters is due to both the number and degradative species secreted by the macrophages. It is possible that adsorbed vitronectin alters how macrophages are activated and what kind of degradative species they secrete. Proteomics Core Facility, Center for High Throughput Biology, University of British Columbia; NSERC 20/20 Ophthalmic Biomaterials Network; NSERC CREATE Biointerfaces Training Program