Strontium chloride hexahydrate srcl2 6h2o

Rare earth (RE) oxides: Er₂O₃ and Yb₂O₃ (99.99%, Stanford Materials, United States) were dissolved separately in hydrochloric acid, HCl (ultra-pure, Sigma-Aldrich, 37%, Poland) in order to obtain respective rare earth chloride solutions in a concentration of 1 or 0.25 M. Ammonium fluoride, NH₄F (98+%, Sigma-Aldrich, Poland) was used as the source of fluoride ions. Strontium chloride hexahydrate SrCl₂·6H₂O (Sigma-Aldrich, 99+%, Poland), citric acid trisodium salt dihydrate, (Sigma-Aldrich, 97%, Poland) and ammonium citrate tribasic, (Sigma-Aldrich, ≥97%, Poland), phosphate buffered saline (BioShop), poly(ethylene glycol) bis(carboxymethyl) ether (average M_n 250, Sigma-Aldrich, Poland), polyacrylic acid (average M_w 1800, Sigma – Aldrich, Poland) were used as received, without further purification. Deionized water was used for the synthesis.

Cells were cultured without (Ctrl) or with one of four increasing Sr concentrations, according to a previous study (Bizelli‐Silveira et al., 2018), defining the group they were allocated to Sr1, the physiological level of Sr in the human serum (11.3 × 10⁻³ mg/L); Sr2 (human seric concentration reached after culture with a common Sr systemic supplementation used by osteoporotic women, 13 mg/L); Sr3, 10 times the Sr2 concentration (130 mg/L); and Sr4, approximately 30 times the Sr2 concentration (360 mg/L). Sr was added as strontium chloride hexahydrate (SrCl₂·6H₂O, Sigma‐Aldrich, St. Louis, USA).