ABSTRACT
Gamma irradiated synthetic hydroxyapatite, bone substituting materials NanoBone(®) and HA Biocer were examined using EPR spectroscopy and compared with powdered human compact bone. In every case, radiation-induced carbon centered radicals were recorded, but their molecular structures and concentrations differed. In compact bone and synthetic hydroxyapatite the main signal assigned to the CO(2) (-) anion radical was stable, whereas the signal due to the CO(3) (3-) radical dominated in NanoBone(®) and HA Biocer just after irradiation. However, after a few days of storage of these samples, also a CO(2) (-) signal was recorded. The EPR study of irradiated compact bone and the synthetic graft materials suggest that their microscopic structures are different. In FT-IR spectra of NanoBone(®), HA Biocer and synthetic hydroxyapatite the HPO(4) (2-) and CO(3) (2-) in B-site groups are detected, whereas in compact bone signals due to collagen dominate.
Subject(s)
Bone Substitutes/chemistry , Bone Substitutes/radiation effects , Carbon/chemistry , Coated Materials, Biocompatible/radiation effects , Durapatite/chemistry , Gamma Rays , Biocompatible Materials/chemistry , Biocompatible Materials/radiation effects , Carbon/radiation effects , Coated Materials, Biocompatible/chemistry , Drug Combinations , Durapatite/radiation effects , Electron Spin Resonance Spectroscopy , Free Radicals/radiation effects , Humans , Powders , Silicon Dioxide/chemistry , Silicon Dioxide/radiation effects , Spectroscopy, Fourier Transform InfraredABSTRACT
Aspartic acid (Asp) and asparagine (Asn) are vulnerable amino acids. One-electron addition or withdrawal reactions initiate many deleterious processes involving these amino acids. To study these redox processes we have irradiated by gamma-rays asparagine or aspartic acid in the solid state. The nature of the resulting free radicals was determined by electron paramagnetic resonance (EPR) and by calculations using DFT methods in various environments. Reactions initiated by electron transfer are different for both amino acids: Asn anion loses hydrogen atom whereas the cation undergoes decarboxylation. Conversely, Asp cation loses hydrogen atom from amine group, which triggers decarboxylation.
Subject(s)
Asparagine/radiation effects , Aspartic Acid/radiation effects , Asparagine/chemistry , Aspartic Acid/chemistry , Decarboxylation , Electron Spin Resonance Spectroscopy , Free Radicals/chemistry , Gamma Rays , Molecular Conformation/radiation effectsABSTRACT
Irradiated samples of deproteinized powdered human bone (femur) have been examined by electron paramagnetic resonance (EPR) spectroscopy in X, Q and W bands. In the bone powder sample only one type of CO2- radical ion is stabilized in the hydroxyapatite structure in contrast to powdered human tooth enamel, a material also containing hydroxyapatite, widely used for EPR dosimetry and in which a few radicals are stable at room temperature. It is suggested that the use of deproteinized bone for EPR dosimetry could improve the accuracy of dose determination.
