In vitro biodegradability–bioactivity–biocompatibility and antibacterial properties of SrF2 nanoparticles synthesized by one-pot and eco-friendly method based on ternary strontium chloride-choline chloride-water deep eutectic system

Abstract

Strontium fluoride (SrF2) nanoparticles were synthesized using strontium chloride-choline chloride-water deep eutectic system at 80 °C. XRD, FESEM, TEM, EDS and Raman spectroscopy were employed to characterize the synthesized nanoparticles. The analytical results confirmed the synthesis of SrF2 nanoparticles crystallized in the cubic crystal system with a mean crystal diameter of 26 nm, average particle size of 40 nm, Sr/F atomic ratio of 1.85 and high elemental and structural purity. The biodegradation and bioactivity of as-synthesized SrF2 nanoparticles were examined in the artificial saliva (AS) and simulated body fluid (SBF). The nanoparticles showed maximum weight loss of 33% after immersion in the AS solution for 14 days. The results of SEM-EDS and Raman spectroscopy revealed the formation of a dense apatite layer on the surface of the nanoparticles after 14 days of incubation in the SBF suggesting the good in vitro bioactivity. Antibacterial study demonstrated the excellent antibacterial activity of SrF2 nanoparticles against the Streptococcus mutans in such a way that ~ 100% bacteria elimination was achieved in presence of the nanoparticles compared with control. This was attributed to the increase of pH and osmotic pressure of the environment caused by the enhanced release of Sr2+ and F– ions from the synthesized SrF2 nanoparticles. MTT cytotoxicity assay and acridine orange (AO) staining test on the human mesenchymal stem cells (hMSCs) confirmed the biocompatibility of SrF2 nanoparticles.