In vitro osteogenesis by intracellular uptake of strontium containing bioactive glass nanoparticles.

Title In vitro osteogenesis by intracellular uptake of strontium containing bioactive glass nanoparticles.
Authors P. Naruphontjirakul; A.E. Porter; J.R. Jones
Journal Acta Biomater
DOI 10.1016/j.actbio.2017.11.008

Monodispersed strontium containing bioactive glass nanoparticles (Sr-BGNPs) with two compositions were synthesised, through a modified sol-gel Stöber process, wherein silica nanoparticles (SiO2-NPs) were formed prior to incorporation of calcium and strontium, with diameters of 90?±?10?nm. The osteogenic response of a murine preosteoblast cell line, MC3T3-E1, was investigated in vitro for a nanoparticle concentration of 250?µg/mL with compositions of 87?mol% SiO2, 7?mol% CaO, 6?mol% SrO and 83?mol% SiO2, 3?mol% CaO, 14?mol% SrO. Dissolution studies in minimum essential media (?-MEM) at pH 7.4 and artificial lysosomal fluid (ALF) at pH 4.5 showed that the particles dissolved and that Sr2+ ions were released from Sr-BGNPs in both environments. Both particle compositions and their ionic dissolution products enhanced the alkaline phosphatase (ALP) activity of the cells and calcium deposition. Immunohistochemistry (IHC) staining of Col1a1, osteocalcin (OSC) and osteopontin (OSP) showed that these proteins were expressed in the MC3T3-E1 cells following three weeks of culture. In the basal condition, the late osteogenic differentiation markers, OSC and OSP, were more overtly expressed by cells cultured with Sr-BGNPs with 14?mol% SrO and their ionic release products than in the control condition. Col1a1 expression was only slightly enhanced in the basal condition, but was enhanced further by the osteogenic supplements. These data demonstrate that Sr-BGNPs accelerate mineralisation without osteogenic supplements. Sr-BGNPs were internalised into MC3T3-E1 cells by endocytosis and stimulated osteogenic differentiation of the pre-osteoblast cell line. Sr-BGNPs are likely to be beneficial for bone regeneration and the observed osteogenic effects of these particles can be attributed to their ionic release products.

STATEMENT OF SIGNIFICANCE: We report, for the first time, that monodispersed bioactive glass nanoparticles (?90?nm) are internalised into preosteoblast cells by endocytosis but by unspecific mechanisms. The bioactive nanoparticles and their dissolution products (without the particles present) stimulated the expression of osteogenic markers from preosteoblast cells without the addition of other osteogenic supplements. Incorporating Sr into the bioactive glass nanoparticle composition, in addition to Ca, increased the total cation content (and therefore dissolution rate) of the nanoparticles, even though nominal total cation addition was constant, without changing size or morphology. Increasing Sr content in the nanoparticles and in their dissolution products enhanced osteogenesis in vitro. The particles therefore have great potential as an injectable therapeutic for bone regeneration, particularly in patients with osteoporosis, for which Sr is known to be therapeutic agent.

Citation P. Naruphontjirakul; A.E. Porter; J.R. Jones.In vitro osteogenesis by intracellular uptake of strontium containing bioactive glass nanoparticles.. Acta Biomater. 2018;66:6780. doi:10.1016/j.actbio.2017.11.008

Related Elements


See more Strontium products. Strontium (atomic symbol: Sr, atomic number: 38) is a Block S, Group 2, Period 5 element with an atomic weight of 87.62 . Strontium Bohr ModelThe number of electrons in each of Strontium's shells is [2, 8, 18, 8, 2] and its electron configuration is [Kr] 5s2. The strontium atom has a radius of 215 pm and a Van der Waals radius of 249 pm. Strontium was discovered by William Cruickshank in 1787 and first isolated by Humphry Davy in 1808. In its elemental form, strontium is a soft, silvery white metallic solid that quickly turns yellow when exposed to air. Elemental StrontiumCathode ray tubes in televisions are made of strontium, which are becoming increasingly displaced by other display technologies pyrotechnics and fireworks employ strontium salts to achieve a bright red color. Radioactive isotopes of strontium have been used in radioisotope thermoelectric generators (RTGs) and for certain cancer treatments. In nature, most strontium is found in celestite (as strontium sulfate) and strontianite (as strontium carbonate). Strontium was named after the Scottish town where it was discovered.

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