Intracellular pathway and subsequent transformation of hydroxyapatite nanoparticles in the SAOS‐2 osteoblast cell line

Abstract

Internalization of hydroxyapatite nanoparticles in SAOS-2 osteoblasts for 2 and 24 h was investigated in vitro using 5 and 50 µg/mL nanoparticles in culture medium. No cytotoxic effects were observed in a PrestoBlue viability assay. Focused ion beam-scanning electron microscopy and transmission electron microscopy were used to study nanoparticle trafficking inside cells and to characterize the physicochemical properties of the remodeled nanoparticles. Nanoparticles were actively internalized by cells and maintained in intracellular membrane-bound compartments. Dissolution of hydroxyapatite nanoparticles was observed inside phagolysosome in all samples. After 24 h of internalization in cell culture assays, reprecipitation of calcium phosphate minerals was observed in membrane-bound compartments in 5 and 50 µg/mL samples. Compared to the original nanoparticles, the reprecipitated calcium phosphate phase presented a different morphology, structure, and chemical composition. Two sample preparation methods were used and confirmed that reprecipitation of the calcium phosphate crystallites occurred in the intracellular environment and not during electron microscopy sample preparation. Reprecipitation of calcium phosphate prevented the release of large amounts of calcium and phosphate ions inside the cells. This phenomenon may be linked to physiological processes in the cell that control the concentration and trafficking of intracellular calcium ions, which are highly controlled by cells. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 428-439, 2018.

Transformation Cycle of Magnetosomes in Human Stem Cells: From Degradation to Biosynthesis of Magnetic Nanoparticles Anew

“…This dissolution / biosynthesis mechanism resembles to the one observed with other nanomaterial compositions, such as hydroxyapatite nanocrystals that are fully dissolved and re-precipitate as needle-like crystallites within one day. 44 The natural presence of magnetite nanoparticles has been detected in a variety of human cells including in the brain, heart, spleen, liver, ethmoid bone, and tumors, [45][46][47][48][49] and has sometimes been designated as an indicator of neurodegenerative diseases. [50][51][52] However, the reason for their presence remains unexplained.…”

Impact of crystallinity and crystal size of nanostructured carbonated hydroxyapatite on pre‐osteoblast in vitro biocompatibility

“…In this sense, the presence of aggregates and nanoparticles may provide a yet untested hypothesis for a possible alternative nutrient source: since substantial interaction of NPs/aggregates with the cell surface were observed, as well as high internalization levels, they might have compensated for medium depletion by providing proteins and ions internally or in the cell vicinity. In this sense, a recent work has shown that HA nanoparticles internalized in high amounts by osteoblasts were able to increase calcium and phosphate levels in the cytoplasm, even causing reprecipitation of calcium phosphates inside the cell (Rossi et al, ). The morphological and ultrastructural evaluations are in accordance with the observed lack of cytotoxicity, since the overall morphological features of the cells were quite similar to those of the control (unexposed) group, even when cell surfaces were overloaded with particles and aggregates (noncentrifuged samples).…”

Nanosized hydroxyapatite and β-tricalcium phosphate composite: Physico-chemical, cytotoxicity, morphological properties and in vivo trial

“…Results from the literature indicate that, a few months after grafting surgery, synthetic hydroxyapatite regenerates the bone 7 . The results with micro-CT (μ-CT) confirmed histological data.…”