Effects of ionizing radiation in the diagnostic and therapeutic range on the biophysical properties of collagen fibrils.

Background Ionizing radiation may indiscriminately and adversely affect tissues during exposure. As collagen is the most abundant protein in the human body, its exposure to ionizing radiation is inevitable. To date, there has been limited comprehensive evaluation of the biophysical properties of individual collagen fibrils exposed to clinically relevant doses of ionizing radiation. Objective To assess the effects of ionizing radiation at diagnostic and therapeutic levels on the biophysical properties of collagen at the nanoscale. Study Design In vitro acellular type I collagen scaffolds (rat tail origin) were irradiated at two relevant dose levels (diagnostic regime D = 50 µGy and therapeutic regime D = 70 Gy (single fraction)) in hydrated and dehydrated states. Alterations in the biophysical properties of these scaffolds were assessed using atomic force microscopy (AFM) (imaging, nanoindentation) and attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy. Results Preliminary analysis demonstrated changes in Young's modulus for all samples treated with both diagnostic and therapeutic dose levels, suggesting the presence of internal crosslinking modifications. These hypothesized changes will be further evaluated by fluorescence-lifetime imaging microscopy (FLIM) and dielectric analysis. No changes were detected in the infrared spectrum, suggesting no denaturation of the protein structure. A neural network for texture analysis is in development for AFM image processing and dose correlation quantification. Conclusion In this exploratory project, we demonstrated that diagnostic and therapeutic levels of radiation can alter Young's modulus of individual collagen fibers. Evaluation of irradiated collagen changes may prove important in managing oral diseases such as squamous cell carcinoma and radiation-induced mucositis and caries. Additional imaging and image processing studies are ongoing to further characterize the response of collagen to radiation. Statement of Ethical Review Ethical Review or exemption was not warranted for this study Ionizing radiation may indiscriminately and adversely affect tissues during exposure. As collagen is the most abundant protein in the human body, its exposure to ionizing radiation is inevitable. To date, there has been limited comprehensive evaluation of the biophysical properties of individual collagen fibrils exposed to clinically relevant doses of ionizing radiation. To assess the effects of ionizing radiation at diagnostic and therapeutic levels on the biophysical properties of collagen at the nanoscale. In vitro acellular type I collagen scaffolds (rat tail origin) were irradiated at two relevant dose levels (diagnostic regime D = 50 µGy and therapeutic regime D = 70 Gy (single fraction)) in hydrated and dehydrated states. Alterations in the biophysical properties of these scaffolds were assessed using atomic force microscopy (AFM) (imaging, nanoindentation) and attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy. Preliminary analysis demonstrated changes in Young's modulus for all samples treated with both diagnostic and therapeutic dose levels, suggesting the presence of internal crosslinking modifications. These hypothesized changes will be further evaluated by fluorescence-lifetime imaging microscopy (FLIM) and dielectric analysis. No changes were detected in the infrared spectrum, suggesting no denaturation of the protein structure. A neural network for texture analysis is in development for AFM image processing and dose correlation quantification. In this exploratory project, we demonstrated that diagnostic and therapeutic levels of radiation can alter Young's modulus of individual collagen fibers. Evaluation of irradiated collagen changes may prove important in managing oral diseases such as squamous cell carcinoma and radiation-induced mucositis and caries. Additional imaging and image processing studies are ongoing to further characterize the response of collagen to radiation.