Laser Modification of Surface Crystallinity of Biodegradable Polymers

这笔赠款为研究激光修饰生物可降解聚合物的表面结晶度提供了资金。在脉冲激光照射下的热过程，包括表面的快速熔化和随后的高猝灭速率，以及聚合物的缓慢结晶动力学，都会产生结晶度降低的表层。由于水解降解速率是聚合物结晶度的强烈函数，因此可以利用该工艺来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)，因为它们是美国食品和药物管理局批准的，如果是溶剂浇注的话是结晶的，并且具有理想的机械性能。将进行结晶度的深度剖析和降解测试，以将沿深度的变化与质量损失测量相关联。将研究激光处理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仪(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学和微观结构的演变来预测降解、重量损失和腐蚀率。如果成功，这项技术可能会影响到广泛的应用，如固定装置、缝合线、组织工程、药物输送、农药喷洒和包装。特别是，基于本体侵蚀聚合物的药物输送系统可以从设计理想的降解型从而控制药物释放型的能力中受益。与最佳的装置形状和尺寸设计相结合，这项技术可能有助于调整给药装置的药物释放速率，以实现预期的治疗效果。对均聚物PLLA激光加工的深入了解，将有助于深入了解激光与其他半结晶生物可降解共聚物的相互作用。

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.