Bioglass implant-coating interactions in synthetic physiological fluids with varying degrees of biomimicry

Abstract

Synthetic physiological fluids are currently used as a first in vitro bioactivity assessment for bone grafts. Our understanding about the interactions taking place at the fluid–implant interface has evolved remarkably during the last decade, and does not comply with the traditional International Organization for Standardization/final draft International Standard 23317 protocol in purely inorganic simulated body fluid. The advances in our knowledge point to the need of a true paradigm shift toward testing physiological fluids with enhanced biomimicry and a better understanding of the materials’ structure-dissolution behavior. This will contribute to “upgrade” our vision of entire cascades of events taking place at the implant surfaces upon immersion in the testing media or after implantation. Starting from an osteoinductive bioglass composition with the ability to alleviate the oxidative stress, thin bioglass films with different degrees of polymerization were deposited onto titanium substrates. Their biomineralization activity in simulated body fluid and in a series of new inorganic–organic media with increasing biomimicry that more closely simulated the human intercellular environment was compared. A comprehensive range of advanced characterization tools (scanning electron microscopy; grazing-incidence X-ray diffraction; Fourier-transform infrared, micro-Raman, energy-dispersive, X-ray photoelectron, and surface-enhanced laser desorption/ionization time-of-flight mass spectroscopies; and cytocompatibility assays using mesenchymal stem cells) were used. The information gathered is very useful to biologists, biophysicists, clinicians, and material scientists with special interest in teaching and research. By combining all the analyses, we propose herein a step forward toward establishing an improved unified protocol for testing the bioactivity of implant materials.

Synthesis and bioactivity assessment of high silica content quaternary glasses withCa:Pratios of 1.5 and 1.67, made by a rapid sol‐gel process

“…The in vitro bioactivity in SBF was assessed by immersion of 58.5 and 59.2 mg of glass powders from samples 1.5 and 1.67 , respectively, in 50 mL of SBF solution at 37°C following a unified approach recommended elsewhere . The ionic concentrations of the SBF (Na + = 142.0, K + = 5.0, Ca 2+ = 2.5, Mg 2+ = 1.5, CI – = 125.0, = 1.0, = 27.0 and = 0.5 mmol L −1 ) are virtually equivalent to those of human plasma .…”

Bioactive calcium phosphate–based glasses and ceramics and their biomedical applications: A review

“…148 DMEM contains lower concentration of Ca 2+ ions but higher concentration of ${\mathrm{HCO}}_3^{-}$ ions compared to blood plasma which leads to formation of CaCO 3 instead of apatite. 148 However, recently Popa et al 149 studied the in vitro bioactivity of BG films (SiO 2 38.5, CaO 36.1, P 2 O 5 5.6, MgO 15.2, ZnO 4, and CaF 2 0.6 in mol%) in different medium (namely SBF, DMEM, DMEM supplemented with 10% foetal bovine serum) and found that bioactivity test in DMEM supplemented with proteins under homeostatic conditions was more appropriate than that in SBF. They also suggested an unique bioactivity testing protocol utilising specific surface area to medium volume ratio (Sa/V = 0.5 cm 2 /mL) for the materials with different shapes and dimensions including bulk objects, thin films, powder and scaffolds.…”

The effect of sodium and magnesium ions on the properties of calcium–phosphate biomaterials

“…The substitution of magnesium ion in the silicate skeleton affects the structure and properties of the bone. On the other hand, the magnesium ion proceeds as a silicate network modifier (Pet’kov et al 2006; Popa et al 2017). …”

“…There are numerous ways to obtain modified calcium–phosphates, the essence of which is to be precipitated from the salts, calcium oxide or hydroxide using orthophosphoric acid or one and two substituted phosphate salts, followed by hydrolysis in solution, under hydrothermal conditions or as a result of pyrolysis (Pet’kov et al 2006; Popa et al 2017; Kukueva et al 2017). …”

“…It is proved that the presence of silicon in the volume of calcium–phosphate material and on its surface accelerates the fusion of the implant with the bone (osteointegration) (Popa et al 2017; Kukueva et al 2017; Moghanian et al 2018; Vijayalakshmi and Rajeswari 2006; Chrysafi and Perraki 2007; Jmal and Bouaziz 2017). …”