In Vivo Biological Response to Ultrananocrystalline Diamond Particles

Titanium (Ti) is the most widely used biomaterial in dental implantology.  Ultrananocrystalline diamond (UNCD®) has been proposed as a material for the manufacture of coatings, films, and structured surfaces for biomedical implants. Objective: To perform an in vivo study in order to evaluate the biodistribution of, and biological response to UNCD® particles. Methods: Wistar rats (n=15/pg) were intraperitoneally injected with UNCD® particles (1.6g/100g of body weight) or saline solution (controls). Six months post-procedure, blood samples were obtained and the animals were euthanized in order to determine: a) The presence of particle deposits in the liver, lung, and kidneys, and subsequent changes in the tissue, using light and electron microscopy; and b) the occurrence of particle-associated oxidative damage to the liver and lungs, by determination of membrane lipid peroxidation (TBARS), generation of reactive oxygen species (O₂^-), and antioxidant enzymes (SOD, CAT) and non-enzymatic antioxidants (nonprotein thiols-Glutathione). Results: Deposits of UNCD® were found in mononuclear blood cells and in the parenchyma of the studied organs. No alterations associated with the deposits were observed in any of the organs. No membrane damage (TBARS) or mobilization of enzymatic antioxidants was observed in the liver.  However, UNCD® was found to induce a significant decrease in non-enzymatic antioxidants (Co: 27.94±3.57 vs. UNCD®: 14.74±4.76 µmol/mg tissue, p<0.05). No membrane oxidative damage (Co: 1.33±0.46 vs. UNCD®: 1.01±0.38, p>0.05) or variations in O₂^- generation (Co: 35.1±4.02 vs. UNCD®: 48±9.1, p>0.05) were observed in lung tissue either. Conclusion: The studied parameters suggest that Ultrananocrystalline diamond (UNCD®) caused neither biochemical nor histological alterations and it may prove useful as a surface coating for biomedical implants.  Grants: PICT 2008-1116 ANPCyT, UBACyT 200201202001190BA, 20020100100657BA, PIP 11220090100117.  Acknowledgments: Lourdes Cáceres for her technical assistance.