Gallic acid grafting modulates the oxidative potential of ferrimagnetic bioactive glass-ceramic SC-45

Magnetite-containing glass-ceramics are promising bio-materials for replacing bone tissue after tumour resection. Thanks to their ferrimagnetic properties, they generate heat when subjected to an alternated magnetic field. In virtue of this they can be employed for the hyperthermic treatment of cancer. Moreover, grafting anti-cancer drugs onto their surface produces specific anti-neoplastic activity in these biomaterials. Gallic acid (GA) exhibits antiproliferative activity which renders it a promising candidate for anticancer applications. In the present paper, the reactivity of ferrimagnetic glass-ceramic SC-45 grafted with GA (SC-45+GA) was studied in terms of ROS release, rupture of the C-H bond of the formate molecule and Fenton reactivity by EPR/spin trapping in acellular systems. The ability of these materials to cause lipid peroxidation was assessed by UV-Vis/TBA assay employing linoleic acid as a model of membrane lipid. The results, compared to those obtained with SC-45, showed that GA grafting i) significantly enhanced the Fenton reactivity and ii) restored the former reactivity of SC-45 towards both the C-H bond and linoleic acid which had been completely suppressed by prolonged contact with water. Fe2+ centres at the surface are probably implicated. GA, acting as a pro-oxidant, reduces Fe3+ to Fe2+ by maintaining a supply of Fe2+ at the surface of SC-45+GA.