(497a) Tof-SIMS Depth Profiles of Enzymatically Degraded Polyurethanes

Polyurethanes have been widely used in biomaterial applications. Recently novel segmented linear polyurethanes based on lysine diisocyanate, polycaprolactone (PCL) and an oligopeptide diamine were synthesized. The oligopeptide segment contained three amino acid residues, including proline, hydroxyproline and glycine. The hypothesis is that incorporation of peptide-like segments into the polyurethane backbone would provide a synthetic polymer material with a unique combination of desirable mechanical and biodegradation properties. The biodegradation processes in synthetic polymeric implants are initiated at the interface between the biomaterial and the biological environment. Thus, it is important to have a detailed understanding of the biodegradation process, so it can be controlled and optimized for a given biomaterial application. In this work the degradation kinetics of polypeptide-polyurethane (PPUU) samples, as well as polyurethane (PUU) control samples, were studied using time-of-flight Secondary Ion Mass Spectrometry (ToF-SIMS) depth profiling. The polymers were spin coated onto glass slides and unique signals from the three polyurethane components (hard segment, HS, soft segment, SS, and oligopeptide segment, OPS) were identified in the ToF-SIMS data. These signals were then used to acquire ToF-SIMS depth profiles before and after soaking the PUU and PPUU samples in collagenase solutions (Figure 1a). It was observed that including OPS within the urethane chains significantly increased the rate of degradation in a collagenase solution (Figure 1b). Figure 1: (a) The ToF-SIMS depth profile of the PPUU sample after soaking in a collagenase solution for 24 hrs at 37°C. The thickness was determined by the appearance of the silicon signal from the glass substrate; (b) Thicknesses of PPU and PPUU samples determined by ToF-SIMS as a function of exposure time to the collagenase solution.