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

Area of Science:

• Biomaterials Science
• Cell Biology
• Nanotechnology

Background:

• Bone cells, osteoblasts, produce an extracellular matrix (osteoid) mineralized by calcium phosphate (CaP).
• Synthetic CaP nanoparticles (NPs) show clinical potential, but their effects on osteoblasts vary with properties like shape.
• Limited research compares CaP NP shapes, specifically hydroxyapatite (HA NPs), on primary human osteoblast (HOB) survival and behavior.

Purpose of the Study:

• To investigate the biocompatibility and ultrastructural effects of two HA NP shapes on HOBs.
• To compare the influence of round (AR2) and rice-shaped (AR4) HA NPs on osteoblast activity, matrix formation, and viability.

Main Methods:

• Cultured primary human osteoblasts (HOBs) were exposed to round (AR2) and rice-shaped (AR4) HA NPs.
• Ultrastructural responses, extracellular matrix (ECM) formation, and matrix vesicle release were observed.
• Transmission electron microscopy (TEM)-based X-ray microanalysis measured cytoplasmic ion levels (Ca, P, Na, K) to assess cell viability (K/Na ratio).

Main Results:

• Both HA NP shapes increased cytoplasmic ion levels; AR2 NPs demonstrated a greater osteogenic effect (alkaline phosphatase activity, matrix vesicle release) than AR4 NPs.
• Cell viability, assessed by K/Na ratios, was best maintained with AR2 NPs.
• ECM formation was altered by both HA NP shapes, with fibronectin and matrilin-3 identified as affected proteins; matrilin-3 expression by osteoblasts is newly described.

Conclusions:

• HA NP shape significantly influences osteoblast viability and activity.
• Rounder HA NPs (AR2) exhibit superior osteogenic potential and cell viability compared to rice-shaped HA NPs (AR4).
• Specific intracellular Ca and P concentrations may be critical for optimal osteoblast function.