Titanium particles that have undergone phagocytosis by macrophages lose the ability to activate other macrophages

• Published in: Journal of biomedical materials research. Part B, Applied biomaterials Vol. 85B; no. 1; pp. 37 - 41
• Main Authors: Xing, Zhiqing, Schwab, Luciana P., Alley, Carie F., Hasty, Karen A., Smith, Richard A.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.04.2008
• Subjects: Alloys - chemistry; Alloys - metabolism; Biocompatible Materials - metabolism; Cell Survival; Culture Media - chemistry; Culture Media - metabolism; Hip Prosthesis; Humans; Lipopolysaccharides - immunology; macrophage; Macrophage Activation; Macrophages - cytology; Macrophages - immunology; osteolysis; particle; Particle Size; phagocytosis; Phagocytosis - physiology; Prosthesis Failure; Titanium - immunology; Tumor Necrosis Factor-alpha - immunology
• ISSN: 1552-4973; 1552-4981
• DOI: 10.1002/jbm.b.30913

Titanium particles derived from the wear of the orthopaedic implant surfaces can activate macrophages to secrete cytokines and stimulate osteoclastic bone resorption, causing osteolysis around orthopaedic implants. However, what happens to the titanium particles after being phagocytosed by macrophages is not known. We prepared titanium particles (as received, clean, and LPS‐coated), and exposed them to macrophages in culture. Free particles were washed away after 24 h and the intracellular particles were kept in culture for additional 48 h until being harvested by lysing the cells. Particles that had been cell treated or noncell treated were examined by scanning electronic microscopy to analyze the shape, size, and concentration of the particles. The cell treated and noncell treated particles were exposed to macrophages in culture with a particle to cell ratio of 300:1. After 18 h, the levels of TNF‐α in culture medium and the viability of the cells were examined. Clean particles did not stimulate TNF‐α secretion by macrophages, while LPS‐coated particles dramatically increased that response. Phagocytosis by macrophages did not change the shape and size of the particles, but depleted the ability of the particles to stimulate TNF‐α secretion by macrophages. This indicates that macrophages are capable of rendering titanium particles inactive without degrading the particles, possibly by altering the surface chemistry of the particles. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008