Nanohydroxyapatite shape and its potential role in bone formation: an analytical study

Abstract

Bone cells (osteoblasts) produce a collagen-rich matrix called osteoid, which is mineralized extracellularly by nanosized calcium phosphate (CaP). Synthetically produced CaP nanoparticles (NPs) have great potential for clinical application. However few studies have compared the effect of CaP NPs with different properties, such as shape and aspect ratio, on the survival and behaviour of active bone-producing cells, such as primary human osteoblasts (HOBs). This study aimed to investigate the biocompatibility and ultrastructural effects of two differently shaped hydroxyapatite [Ca 10 (PO 4 ) 6 (OH) 2 ] nanoparticles (HA NPs), round-(aspect ratio 2.12, AR2) and rice-shaped (aspect ratio 3.79, AR4). The ultrastructural response and initial extracellular matrix (ECM) formation of HOBs to HA NPs were observed, as well as matrix vesicle release. A transmission electron microscopy (TEM)-based X-ray microanalytical technique was used to measure cytoplasmic ion levels, including calcium (Ca), phosphorus (P), sodium (Na) and potassium (K). K/Na ratios were used as a measure of cell viability. Following HA NP stimulation, all measured cytoplasmic ion levels increased. AR2 NPs had a greater osteogenic effect on osteoblasts compared with AR4 NPs, including alkaline phosphatase activity and matrix vesicle release. However, they produced only a moderate increase in intracellular Ca and P levels compared with AR4. This suggests that particular Ca and P concentrations may be required for, or indicative of, optimal osteoblast activity. Cell viability, as measured by Na and K microanalysis, was best maintained in AR2. Initial formation of osteoblast ECM was altered in the presence of either HA NP, and immuno-TEM identified fibronectin and matrilin-3 as two ECM proteins affected. Matrilin-3 is here described for the first time as being expressed by cultured osteoblasts. In summary, this novel and in-depth study has demonstrated that HA NP shape can influence a range of different parameters related to osteoblast viability and activity.

In vitro degradability, bioactivity and primary cell responses to bone cements containing mesoporous magnesium–calcium silicate and calcium sulfate for bone regeneration

“…The apatite layer formation on biomaterials in the biological environment plays an important role in the formation of chemical bonds between material surfaces and bone tissues, as well as bone-relating progress [24,25]. In our research, the m-CSBC could induce apatite deposition within one week, while little apatite was observed on the CSBC surface.…”

Calcium orthophosphates (CaPO 4 ): Occurrence and properties

“…Presumably, a synthesis of various types of CaPO 4 -based biocomposites and hybrid biomaterials occupies the second important place (Dorozhkin 2015b). The third important place is occupied by investigations devoted to the synthesis and characterization of various nano-sized particles and nanodimensional crystals of CaPO 4 (Dorozhkin 2013d), ACP (Dorozhkin 2012c), as well as CaPO 4 with controlled particle geometry and shapes Galea et al 2013;Kalia et al 2014). In general, the geometry of crystal phases can be varied by controlling the precipitation conditions, such as temperature, solution pH, concentration of the reagents, hydrodynamics, presence of various admixtures, inhibitors or promoters and ultrasonication.…”

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

“…Different cell types have been used to investigate the internalization of CP‐NPs in vitro , such as osteoblasts, human monocyte‐derived macrophages, human epithelial cells, human hepatoma HepG2 cells, and human polymorphonuclear leucocytes . In all these cases, NP uptake was an active mechanism that was dependent upon the NP physical–chemical properties.…”

“…CP‐NPs are highly reactive, and when present in high concentrations (>100 µg/mL), they can sequester a large number of ions from the culture medium (modifying the ion concentration in the medium) and indirectly cause cytotoxicity. Different morphologies, compositions, surface charges, and sizes may induce different cellular responses, such as proliferation, ultrastructural changes, disturbance of cytoplasmic ion levels, and expression of proteins involved in mineralization …”