Laser Modification of Surface Crystallinity of Biodegradable Polymers

该补助金为研究激光改性可生物降解聚合物的表面结晶度提供资金。 在脉冲激光照射中的热过程，包括在表面处的快速熔化和随后的高淬火速率，结合聚合物的缓慢结晶动力学，产生具有降低的结晶度的表面层。由于水解降解速率是聚合物结晶度的强函数，因此该方法可用于改变此类聚合物的降解曲线。该项目将专注于聚（α-羟基酸）聚合物，特别是聚（L-丙交酯）（PLLA），因为它们是USFDA批准的，如果溶剂浇铸，则是结晶，并且具有理想的机械性能。 将进行结晶度和降解试验的深度分析，以将沿着深度的变化与质量损失测量值联系起来。 激光加工参数对化学和分子量变化的影响将被研究。 主要表征包括差示扫描量热法（DSC）、广角X射线衍射仪和衰减全反射傅里叶变换红外光谱（FTIR-ATR）。数值模型将结合传热与微结构演变来预测降解、重量损失和侵蚀速率。如果成功，该技术可能会影响广泛的应用，如固定装置、缝合线、组织工程、药物输送、杀虫剂传播和包装。 特别地，基于本体侵蚀聚合物的药物递送系统可以受益于设计期望的降解曲线和因此受控的药物释放曲线的能力。 结合最佳的装置形状和尺寸设计，该技术可以潜在地帮助定制递送装置中的药物释放速率，以实现所需的治疗效果。 对均聚物PLLA的激光加工的显著先进的理解，将提供对激光与其他半结晶可生物降解共聚物的相互作用的洞察。

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.