During the first year of the project, optimization of the sample preparation protocols and the liquid phase imaging protocols were carried out. Different demineralization and high-pressure freezing vitrification protocols were applied to maximize vitrification depth and sample quality. Cryo-sections thickness, thawing, and remineralization protocols were optimized until the entirely workflow proceeded smoothly. Mineralization experiments were initiated in the LPEM cell by introducing an artificial osteogenic medium at a low and constant flow.
The detection of the early mineral deposits was mainly carried out in STEM mode. However, the interactions of the electrons through the water column (inelastic scattering) lead to the broadening of the electron probe, producing a blurry effect in the image and reducing the spatial resolution. In STEM, beam broadening increases with the depth of the focal plane, limiting the position of the objects that can be imaged. The visualization of mineral particles was achieved, although some optimization of the imaging parameters is still required.