Effects of various man-made mineral fibers on cell apoptosis and viability

In Vitro Molecular Study of Titanium-Niobium Alloy Biocompatibility

Titanium dental implants have common clinical applications due to their biocompatibility, biophysical and biochemical characteristics. Although current titanium is thought to be safe and beneficial for patients, there are several indications that it may release toxic metal ions or metal nanoparticles from its alloys into the surrounding environment, which could lead to clinically relevant complications including toxic reactions as well as immune dysfunctions. Hence, an adequate selection and testing of medical biomaterial with outstanding properties are warranted. This study was designed to explore the biocompatibility of smooth titanium-niobium alloy (S_TiNb) versus smooth titanium commercially pure (S_TiCp)—a reference in implantology. All experiments were performed in vitro using human osteoblast-like SaOs-2 and monocyte THP-1 cell lines as models. Cell adhesion and growth morphology were determined by scanning electron microscopy, while cell viability was evaluated using WST-1 assay. Because niobate anions or niobium nanoparticles can be released from implants during biomaterial-cell interaction, potential immunotoxicity of potassium niobate (KNbO₃₎ salt was evaluated by examining both metabolic activity and transcriptomic profiling of treated THP-1 monocytes. The main findings of this study are that S_TiCp and S_TiNb discs do not show an impact on the proliferation and viability of SaOs-2 cells compared to polystyrene surfaces, whereas a significant decrease in THP-1 cells’ viability and metabolic activity was observed in the presence of S_TiNb discs compared to the control group. However, no significant changes were found neither at the metabolic activity nor at the transcriptomic level of THP-1 monocytes exposed to KNbO₃ salt, suggesting that niobium has no effect on the immune system. Overall, these data imply a possible toxicity of S_TiNb discs toward THP-1 cells, which may not be directly related to niobium but perhaps to the manufacturing process of titanium-niobium alloy. Thus, this limitation must be overcome to make titanium alloy an excellent material for medical applications.

Synthetic vitreous fibers: a review toxicology, epidemiology and regulations

This review addresses the characteristics which differentiate synthetic vitreous fibers (SVFs, e.g., fiber glass, stonewool, slagwool, refractory ceramic fibers, etc.), how these influence the potential biopersistence and toxicity, the most recent epidemiological results and the integration of these findings into the health and safety regulations in Europe and the United States. Also presented is the historical basis for the European classification directive. The use and equivalence of the chronic inhalation toxicology and chronic intraperitoneal injection studies in laboratory rodents for evaluation of fiber toxicology is assessed as well as the impact of dose selection and design on the validity of the study. While synthetic vitreous fibers can span a wide range of chemistries, recognition and understanding of the importance of biopersistence (ability to persist in the lung) in fiber toxicity has led to the development of more and more biosoluble fibers (that break down rapidly in the lung). Still, the epidemiological data available which are largely based upon the use of fibers in past decades, indicate that the SVF do not present a human health risk at current exposure levels. The animal toxicology and biopersistence data provide a coherent basis for understanding and evaluating the parameters which affect SVF toxicity. The current regulations are based upon an extensive knowledge base of chronic studies in laboratory rodents which confirm the relationship between chronic adverse effects and the biopersistence of the longer fibers that can not be fully phagocytised and efficiently cleared from the lung. The amorphous structure of synthetic vitreous fibers facilitates designing fibers in use today with low biopersistence. Both the epidemiological data and the animal studies database provide strong assurance that there is little if any health risk associated with the use of SVFs of low biopersistence. IARC (2001) reclassified these fibers from Category 2b to Category 3 (with RCF and special purpose fibers remaining in 2b) an event which has not been common in the history of these monographs.