Laser Modification of Surface Crystallinity of Biodegradable Polymers

这项拨款为研究激光修饰生物可降解聚合物的表面结晶度提供资金。热过程，包括表面的快速熔化和随后的高淬火速率，在脉冲激光照射下，结合聚合物的缓慢结晶动力学，产生结晶度降低的表面层。由于水解降解率是聚合物结晶度的一个强大功能，该过程可以用来改变这种聚合物的降解谱。该项目将专注于聚（a-羟基酸）聚合物，特别是聚（l -丙交酯）（PLLA），因为它们是美国食品药品监督管理局批准的，如果是溶剂铸造，则是结晶的，并且具有理想的机械性能。将进行结晶度深度剖面和降解测试，以将沿深度的变化与质量损失测量联系起来。研究了激光加工参数对化学和分子量变化的影响。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的傅里叶变换红外光谱（FTIR-ATR）。数值模型将结合传热和微观结构演变来预测降解、重量损失和侵蚀速率。如果成功，这项技术将影响广泛的应用，如固定装置、缝合线、组织工程、药物输送、农药传播和包装。特别是，基于大块侵蚀聚合物的药物输送系统可以受益于设计理想降解轮廓的能力，从而可以控制药物释放轮廓。结合最佳的设备形状和尺寸设计，该技术可以潜在地帮助定制药物释放率的输送设备，以实现所需的治疗效果。对均聚PLLA激光加工的深刻理解，将为激光与其他半晶可生物降解共聚物的相互作用提供见解。

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.