Abstract
While the reciprocity between bioceramics and living cells is complex, it is principally governed by the implant’s surface chemistry. Consequently, a deeper understanding of the chemical interactions of bioceramics with living tissue could ultimately lead to new therapeutic strategies. However, the physical and chemical principles that govern these interactions remain unclear. The intricacies of this biological synergy are explored within this paper by examining the peculiar surface chemistry of a relatively new bioceramic, silicon nitride (Si3N4). Building upon prior research, this paper aims at obtaining new insights into the biological interactions between Si3N4 and living cells, as a consequence of the off-stoichiometric chemical nature of its surface at the nanometer scale. We show here yet unveiled details of surface chemistry and, based on these new data, formulate a model on how, ultimately, Si3N4 influences cellular signal transduction functions and differentiation mechanisms. In other words, we interpret its reciprocity with living cells in chemical terms. These new findings suggest that Si3N4 might provide unique new medicinal therapies and effective remedies for various bone or joint maladies and diseases.
Highlights
Bioceramics have a long and valued history in orthopaedics[1]
One of the more obvious and yet intriguing aspects involving the use of silicon nitride as a biomaterial is that H4SiO4, NH4+, NO3−, and N2 are all promptly and copiously available during biological interactions[20]
Upon exposure to SaOS-2 cells, the greatest formation of hydroxyapatite coincided with the presence of Si-Y-Al-O-N phases[9]
Summary
SaOS-2 human osteosarcoma cells were first cultured and incubated in 4.5 g/L glucose DMEM (D-glucose, L-Glutamine, Phenol Red, and Sodium Pyruvate) supplemented with 10% fetal bovine serum. In situ Raman microscopy images were collected on living SaOS-2 cells using a dedicated instrument (RAMANtouch, Nanophoton Co., Osaka, Japan) with a 20x immersion-type optical lens. This spectroscope allowed ultra-fast imaging of up to 400 spectra simultaneously, collecting average spectra in a time faster than the movement of cells. Laser-scanning micrographs of the sample surfaces after exposure to SaOS-2 cells were collected by means of a 3D laser-scanning microscope (VK-X200 K Series, Keyence, Osaka, Japan) using a 150x objective lens, with a numerical aperture of 0.9. Pass energy, voltage step, and dwell time were 10.0 kV x10.0 mA, 10 eV, 0.1 eV, and 100 ms, respectively
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