Department of Materials, Imperial College London, South Kensington Campus, London SW7 2AZ, UK.
Department of Materials, Imperial College London, South Kensington Campus, London SW7 2AZ, UK.
Acta Biomater. 2018 Jan 15;66:67-80. doi: 10.1016/j.actbio.2017.11.008. Epub 2017 Nov 10.
Monodispersed strontium containing bioactive glass nanoparticles (Sr-BGNPs) with two compositions were synthesised, through a modified sol-gel Stöber process, wherein silica nanoparticles (SiO-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% SiO, 7 mol% CaO, 6 mol% SrO and 83 mol% SiO, 3 mol% CaO, 14 mol% SrO. Dissolution studies in minimum essential media (α-MEM) at pH 7.4 and artificial lysosomal fluid (ALF) at pH 4.5 showed that the particles dissolved and that Sr 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.
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.
通过改良的溶胶-凝胶 Stöber 法合成了两种组成的单分散锶含生物活性玻璃纳米颗粒（Sr-BGNPs），其中先形成二氧化硅纳米颗粒（SiO-NPs），然后再掺入钙和锶，粒径为 90±10nm。体外研究了小鼠前成骨细胞系 MC3T3-E1 对纳米颗粒浓度为 250μg/mL 的成骨反应，组成分别为 87mol%SiO、7mol%CaO、6mol%SrO 和 83mol%SiO、3mol%CaO、14mol%SrO。在 pH7.4 的最低必需培养基（α-MEM）和 pH4.5 的人工溶酶体液（ALF）中的溶解研究表明，颗粒在两种环境中溶解，并且 Sr 离子从 Sr-BGNPs 中释放出来。两种颗粒组成及其离子溶解产物均增强了细胞的碱性磷酸酶（ALP）活性和钙沉积。Col1a1、骨钙素（OSC）和骨桥蛋白（OSP）的免疫组织化学（IHC）染色表明，在培养 3 周后，这些蛋白在 MC3T3-E1 细胞中表达。在基础条件下，用含有 14mol%SrO 的 Sr-BGNPs 及其离子释放产物培养的细胞，比对照条件下更明显地表达晚期成骨分化标志物 OSC 和 OSP。Col1a1 的表达在基础条件下仅略有增强，但在成骨补充剂的作用下进一步增强。这些数据表明，Sr-BGNPs 在没有成骨补充剂的情况下加速矿化。Sr-BGNPs 通过内吞作用被内化到 MC3T3-E1 细胞中，并刺激前成骨细胞系的成骨分化。Sr-BGNPs 可能有益于骨再生，并且这些颗粒的观察到的成骨作用可归因于其离子释放产物。
我们首次报道，单分散生物活性玻璃纳米颗粒（约 90nm）通过内吞作用被内化到前成骨细胞中，但通过非特异性机制。生物活性纳米颗粒及其溶解产物（没有颗粒存在）刺激前成骨细胞表达成骨标记物，而无需添加其他成骨补充剂。在生物活性玻璃纳米颗粒组成中加入 Sr，除了 Ca 之外，还增加了纳米颗粒的总阳离子含量（因此溶解速率），即使总阳离子添加量保持不变，纳米颗粒的尺寸和形态也没有改变。增加纳米颗粒及其溶解产物中的 Sr 含量增强了体外成骨作用。因此，这些颗粒作为一种可注射的骨再生治疗剂具有巨大的潜力，特别是在骨质疏松症患者中，Sr 是已知的治疗剂。
