Abstract
The addition of cerium oxide to bioactive glasses, important materials for bone tissue regeneration, has been shown to induce multifunctionality, combining a significant bioactivity with antioxidant properties. We provide a real time investigation of the evolution of the electronic properties of highly diluted cerium ions in a liquid environment containing hydrogen peroxide - the most abundant reactive oxygen species in living cells. This challenging task is undertaken by means of high-energy resolution fluorescence detected by X-ray absorption near-edge spectroscopy at the Ce L3 edge. We investigate samples with variable compositions and different morphologies. We relate the observed spectroscopic changes not only to variations in the concentration of the two Ce oxidation states in the samples, but also to changes in the local atomic environment of Ce ions, providing a clear picture of the role of cerium ions in the dissociation of hydrogen peroxide. The obtained results contribute to the understanding of the mechanisms that come into play in the process and provide a basis for the optimization of the functionalities of this class of materials.
Highlights
Hydrogen peroxide (H2O2) is one of the most abundant reactive oxygen species (ROS) in living cells, and it is responsible for oxidative damage 1
The first step of the fitting procedure consisted in fitting the spectrum of the sample with the highest Ce4+ concentration, i.e. the spectrum of the MBG4+ sample acquired after 140 min of reaction, with the nine fitting components, fixing the energy positions to the values obtained by fitting the Ce4+ reference spectrum and using the intensities and the widths of the peaks as fitting parameters
When cerium oxide is introduced in glasses as a low-concentration additive the average local atomic environment of Ce ions, and in particular its coordination and
Summary
Hydrogen peroxide (H2O2) is one of the most abundant reactive oxygen species (ROS) in living cells, and it is responsible for oxidative damage 1. The inflammation which often follows increases the generation of ROS, and it induces a situation of oxidative stress This imbalance propagates the inflammation, which may need a long time to achieve a complete recovery 8. In this scenario, reducible oxides, such as cerium oxide, which are effective in the conversion of ROS to non-dangerous species, represent good candidates as additives for biomaterials, to confer additional enzyme-like antioxidant properties. Glasses with a slightly different composition and a mesoporous morphology have recently shown to have a higher catalase mimetic activity, as well as a higher bioactivity compared to molten glasses, and they represent an important step towards the optimization of the material multi-functionalities 14. The design of an in-situ experiment is quite challenging, since it requires a liquid
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