Laser Modification of Surface Crystallinity of Biodegradable Polymers

Columbia University, New York NY

Investigators

Abstract

This grant provides funding for investigating laser modifying the surface crystallinity of biodegradable polymers. Thermal processes, including rapid melting at the surface and subsequent high quench rates, in pulsed laser irradiation in conjunction with slow crystallization kinetics of the polymers produce a surface layer with reduced crystallinity. Since hydrolytic degradation rates are a strong function of polymer crystallinity, the process can be utilized to alter degradation profiles of such polymers. The project will focus on poly (a-hydroxy acid) polymers, especially poly (L-lactide) (PLLA), as they are USFDA approved, are crystalline if solvent cast, and have desirable mechanical properties. Depth profiling of crystallinity and degradation testing will be conducted to relate changes along the depth with mass loss measurements. Effects of laser processing parameters on chemical and molecular weight changes will be investigated. Primary characterizations include Differential Scanning Calorimetry (DSC), Wide Angle X-ray Diffractometer, and Fourier Transform Infrared spectroscopy in Attenuated Total Reflectance (FTIR-ATR). Numerical models will incorporate heat transfer with microstructure evolution to predict degradation, weight loss and erosion rate. If successful, the technology could impact a wide range of applications such as fixation devices, sutures, tissue engineering, drug delivery, pesticide dissemination, and packaging. In particular, drug delivery systems based on bulk eroding polymers can benefit from the ability of designing a desirable degradation profile and thus a controlled drug releasing profile. In conjunction with optimum device shape and size design, the technology can potentially help tailor drug release rates in delivery devices to enable desired therapeutic effects. Significantly advanced understanding of laser processing of homopolymer PLLA, will provide insight into laser interactions with other semicrystalline biodegradable copolymers.