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Influence of particle surface area on the toxicity of insoluble manganese dioxide dusts
1Industrial Toxicology and Occupational Medicine Unit, Catholic University of Louvain, Brussels, Belgium.
Abstract:
The objective of this study was to examine the influence of specific surface area on the biological activity of insoluble manganese dioxide (MnO2) particles. The biological responses to various MnO2 dusts with different specific surface area (0.16, 0.5, 17 and 62 m2/g) were compared in vitro and in vivo. A mouse peritoneal macrophage model was used to evaluate the in vitro cytotoxic potential of the particles via lactate dehydrogenase (LDH) release. In vivo, the lung inflammatory response was assessed by analysis of bronchoalveolar lavage after intratracheal instillation in mice (LDH activity, protein concentration and cellular recruitment). In both systems, the results show that the amplitude of the response is dependent on the total surface area which is in contact with the biological system, indicating that surface chemistry phenomena are involved in the biological reactivity. Freshly ground particles with a specific surface area of 5 m2/g were also examined in vitro. These particles exhibited an enhanced cytotoxic activity, which was almost equivalent to that of 62 m2/g particles, indicating that undefined reactive sites produced at the particle surface by mechanical cleavage may also contribute to the toxicity of insoluble particles. We conclude that, when conducting studies to elucidate the effect of particles on the lung, it is important for insoluble particles such as manganese dioxide to consider the administered dose in terms of surface area (e.g. m2/kg) rather than in gravimetric terms (e.g. mg/kg).
Insights
The biological activity of manganese dioxide (MnO2) particles depends on their specific surface area. Researchers recommend measuring particle dose by surface area, not weight, for lung toxicity studies.
Area of Science:
- Environmental Science
- Toxicology
- Materials Science
Background:
- Insoluble particles, such as manganese dioxide (MnO2), can elicit biological responses.
- Understanding the factors influencing particle toxicity is crucial for risk assessment.
Purpose of the Study:
- To investigate the impact of specific surface area on the biological activity of insoluble MnO2 particles.
- To compare in vitro and in vivo responses to MnO2 dusts with varying surface areas.
Main Methods:
- In vitro cytotoxicity assessed using mouse peritoneal macrophages and lactate dehydrogenase (LDH) release.
- In vivo lung inflammation evaluated in mice via bronchoalveolar lavage analysis (LDH activity, protein, cellularity).
- Comparison of MnO2 particles with specific surface areas of 0.16, 0.5, 17, and 62 m²/g, plus freshly ground particles (5 m²/g).
Main Results:
- Biological responses in both in vitro and in vivo models correlated with the total surface area exposed.
- Freshly ground MnO2 particles exhibited significantly enhanced cytotoxicity, comparable to high-surface-area particles.
- Surface chemistry and reactive sites generated by mechanical cleavage influence MnO2 particle toxicity.
Conclusions:
- The biological reactivity of insoluble MnO2 particles is strongly influenced by their specific surface area.
- Dosing for lung toxicity studies should prioritize surface area (m²/kg) over gravimetric measurements (mg/kg) for insoluble particles.
- Surface properties, including those created by mechanical processing, are critical determinants of particle toxicity.