Multi-frequency electron paramagnetic resonance study of irradiated human finger phalanxes

Area of Science:

• Biophysics
• Materials Science
• Dosimetry

Background:

• Electron paramagnetic resonance (EPR) is a key technique for radiation dosimetry in biological tissues like bone and teeth.
• The mineral component of both bone and teeth is carbonated hydroxyapatite, leading to the assumption of similar radiation-induced radicals.
• Experimental evidence directly comparing EPR signals in bone and tooth enamel remains limited.

Purpose of the Study:

• To experimentally investigate and compare radiation-induced radicals in human bone and tooth enamel using multi-frequency EPR.
• To provide evidence regarding the validity of assuming similar radical formation in bone and enamel for EPR dosimetry.
• To characterize native EPR signals in bone and enamel.

Main Methods:

• Irradiation of human finger phalanx (bone) and tooth enamel samples.
• Analysis of irradiated samples using multi-frequency Electron Paramagnetic Resonance (EPR) spectroscopy.
• Comparison of EPR spectral data between bone and enamel samples.

Main Results:

• Significant differences observed in EPR spectra between bone and enamel samples.
• Apatite crystallite ordering is less in bone, complicating CO2- radical localization.
• One type of CO3(3-) radical was exclusively detected in enamel; distinct non-CO2- and non-CO3(3-) signals were found in both tissues.

Conclusions:

• The assumption of similar radiation-induced radicals in bone and tooth enamel for EPR dosimetry is not fully supported by experimental evidence.
• Differences in crystallite ordering and radical species (e.g., CO3(3-)) highlight tissue-specific characteristics.
• The nature of native EPR signals in bone and enamel requires further investigation.