High levels of ionizing radiation are known to cause degradation and/or cross-linking in polymers. Lower levels of ionizing radiation, such as x-ray and gamma, are commonly used in the treatment of cancers. Material characterization has not been fully explored for polymeric materials exposed to therapeutic radiation levels. Thus, this study investigated the effects of therapeutic radiation on three porous polymeric scaffolds: polycaprolactone (PCL), polyurethane (PU) and gelatin. Porous scaffolds were fabricated by solvent casting and/or salt leeching techniques. Scaffolds were placed in phosphate buffered saline (PBS) and exposed to a typical cancer radiotherapy schedule. A total dose of 50 Gy was broken into 25 dosages over a three-month period. PBS was collected over time and tested for polymer degradation through high performance liquid chromatography (HPLC) and Bicinchoninic Acid (BCA) Protein Assay. Scaffolds were characterized by changes in microstructure using Scanning Electron Microscopy (SEM), and crystallization using Differential Scanning Calorimetry (DSC). Additionally, gelatin e-amine content was analyzed using Trinitrobenzene Sulfonic Acid Assay (TNBSA). Gelatin scaffolds were immersed in PBS for three months without radiation exposure to serve as a control.  The three polymers responded differently to the radiation. For the PCL, no change in molecular weight or microstructure was detected. However, the degree of crystallinity was decreased by 32% from the non-irradiated control. PU displayed both changes in microstructure and a large decrease in crystallinity (85.15%). The gelatin scaffolds responded the most dramatically to the radiotherapy. Samples were observed to swell, and yet maintain shape after exposure while the controls displayed limited swelling followed by degradation. Characterization confirmed degradation and irradiation contributed to the swelling while increased cross-linking through radiation hardening was stabilizing the gelatin. As gelatin was considered a tissue equivalent, further studies on tissues are needed to better understand the effects of therapeutic radiation.

Effects of therapeutic radiation on polymeric scaffolds

247th National Meeting (2014)

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