Carbon-centered radicals in γ-irradiated bone substituting biomaterials based on hydroxyapatite

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.

Influence of gamma and electron beam sterilization on the stability of a premixed injectable calcium phosphate cement for trauma indications

“…Despite the differences, signal II is perhaps related to the CO 2 radical while signal I is potentially associated with a trapped free electron in the material matrix. These results are in agreement with several other studies performed on similar materials following irradiation by ESR analysis (Chróścicka et al, 2016;MatkoviA et al, 2012;Sadlo et al, 2012). Sample G36P24 displayed a notable decrease in the intensity of the signals in particular signal I, suggesting that the annealing step for 24 hours reduced the free radicals generated.…”

Comparison of the Effect of the Amino Acids on Spontaneous Formation and Transformation of Calcium Phosphates

“…For irradiated samples, the main stable component can be assigned to CO − 2 . In previous studies [60][61][62][63][64][65][66][67], it was shown that the EPR spectra of biological, as well as synthetic carbonated calcium apatites, exhibit a complex EPR signal at around g = 2, which comprises several powder spectrum contributions arising from different paramagnetic species (CO − 3 , CO 3− 3 , CO − 2 , O − 3 , O − ) stabilized in different locations (at hydroxyl, phosphate or surface sites) or from the same species, recognized by the difference in g anisotropy. However, as the EPR spectra of apatite are strongly dependent on the conditions of sample preparation (CO 2 flow, drying temperature, annealing procedure, etc.)…”