Paper AS-TuA9
Mapping of a Polymer Surface Reaction: Determination of the Spatially Resolved, Hydrolytic Degradation Kinetics of a Micropatterned Bioresorbable Membrane

Tuesday, October 19, 2010, 4:40 pm, Room Cochiti

Poly(L-lactic acid) (PLLA) is a synthetic, bioresorbable polyester that is extensively used and studied for many [FDA-approved] commercial applications – such as therapeutic drug delivery and tissue engineering scaffolds.¹ It is generally accepted that the degradation process of bioresorbable polyesters: a) is diffusion-based,² b) occurs in a region of finite thickness, forming an erosion front that moves towards the center of a polymer structure,² and c) its rate increases with higher polymer surface area.³ Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) has been previously used to determine initial (before the onset of weight loss) degradation kinetics at bioresorbable polymer surfaces.⁴ This analytical method, combined with the high lateral resolution capabilities of imaging with a bismuth ion source, and image processing algorithms, allowed us to determine the spatially-resolved initial degradation kinetics of micropatterned PLLA membranes at several pH levels. The results show that the degradation reaction occurs at different rates, and that these rates depend on the area of the feature. The findings of this study imply that polymer degradation can be controlled not only in a temporal manner, but also in a microspatial manner, by altering micropattern geometry and size distribution across the polymer membrane.

1. Lee, J, Gardella, Jr., J. Analytical and Bioanalytical Chemistry. 2002. 373. 526.

2. Mathiowitz, E, Jacob, J, Pekarek, K, Chickering III, D. Macromolecules. 1993. 26. 6756.

3. Buchanan, FJ, 2008. Degradation Rate of Bioresorbable Materials: Prediction and Evaluation. Cambridge, UK. Woodhead Publishing Limited.

4. Lee , J, Gardella Jr., J. Analytical Chemistry. 2003. 75. 2950.