Phagocytosis of Simulated Nano-wear Debris by Osteoblasts

In this study I have used well characterized simulated wear-nano-particles of ultra-high molecular weight polyethylene (UHMWPE) of known size and shape to study particulate phagocytosis by MG63 osteoblast-like cells. The particles were treated to decrease their propensity to form aggregates in aqueous suspension and scanning electron microscopy (SEM) was performed to image them as individual particles on 0.01 μm pore size polycarbonate filter membranes. These images were further subjected to morphometric analysis of the particles using ASTM F1877 descriptors [equivalent circle diameter (ECD in μm), aspect ratio (AR), elongation (E), roundness (R), and formfactor (FF)]. The mean (±SD) ECD of the particles were 0.056±0.03 μm. They were subsequently introduced to confluent MG63 cells at particle:cell ratio of 100:1 and incubated for 24 h. Transmission electron micrography (TEM) showed the nanoparticles inside the cytosol. No time dependent response was observed beyond 24 h. The nanoparticles seemed to re-agglomerate once inside the cell. The damage to the cells was evident from the compromised cell membrane. This study will help further our knowledge of the wear-mediated osteolytic process.