An original method to assess short-term physicochemical reactions at the periphery of bioactive glass particles in biological fluids

In this study, we analyze short-term physicochemical reactions at the inter face between bioactive glass particles and biological fluids. The chemical analysis is performed under a micrometer scale by scanning transmission ele ctron microscopy associated to energy-dispersive X-ray spectroscopy. Howeve r, microanalysis of diffusible ions such as sodium, potassium, or oxygen re quires cryomethods for the specimen preparation and for its characterizatio n. These techniques permit retention of all elements at their in vitro loca tion. After 1 day of immersion in biological fluids, results demonstrate th e formation of three surface layers (thickness of each layer approximate to 400 nm) at the bioactive glass periphery. The presence of a Si-Al rich lay er permits the diffusion and the formation of a Ca-P-Mg rich layer. The thi rd layer is composed of Na-O and can be considered as an exchanged layer be tween Na+ ions and H+ or H3O+ from the solution.