The primary particle size of fumed silica is about 7-40nm. It is a typical nanomaterial. As the most widely used and produced nanomaterial in the world, it has thermal stability, chemical inertness, high hydrophilicity and The unique physical and chemical properties such as weak permeability are widely used in many industries, and a large number of them are used in close contact with the human body or directly ingested into the human body. At the same time, mass production and research personnel can enter the relevant occupational groups and contact groups through direct skin contact, respiratory tract inhalation, and digestive tract intake. Due to the active structure and function of nanomaterials, the biosafety and nanotoxicology research of nanomaterials is particularly important for the development and application of nanotechnology. A full understanding of the specific toxicological effects and mechanisms of nano-silica will provide a theoretical basis for the safe research and development of nano-particles in the future and the large-scale application of fumed silica in industries that are in contact with the human body.

Cells are the basic unit of body structure and function. Nano silica has obvious toxic effects on many kinds of cells. The toxicity mechanism of nano-silica is mainly divided into five aspects.

1. Oxidative stress

Oxidative stress is a common toxic mechanism of nanomaterials, and it is also a more critical path of action. Nano-silica itself has high reactivity and high biological activity. After it enters the cell through endocytosis, it can induce the free increase of intracellular superoxide, leading to oxidative stress response and cell damage. Studies have found that nano-silica can cause oxidative stress in multiple organs when entering organisms through different ways.

2. Inflammatory reaction

Nano-silica entering the organism can cause inflammation. Inflammation can cause the degeneration and necrosis of some cells, thereby causing changes in the function of the organism. Nano-silica can increase the risk of inflammatory reactions in the organism, which is the cause of inflammation. One of the mechanisms of biological toxicity.

3. Mitochondrial damage

Mitochondria are the main place where most cells produce energy and the main source of reactive oxygen species in cells. Therefore, mitochondrial damage can cause functional disorders in cells or the body. Nano-silica can change the mitochondrial membrane potential of cardiomyocytes, and hinder the supply of ATP (adenosine triphosphate) of the cells, thereby causing the dysfunction of cardiomyocytes.

4. DNA damage

As a carrier of cytogenetic information, DNA damage will inevitably cause cell dysfunction, thus presenting a corresponding phenotype. Nano-silica can directly destroy the double-stranded structure of DNA by disrupting the cytoskeleton, phosphorylate histones, and make DNA unable to function normally. Nano-silica can directly destroy the structure of the cell nucleus, thereby causing cell apoptosis.

5. Other mechanisms

Nano-silica can cause endoplasmic reticulum stress in a variety of cells, thereby causing cell apoptosis. Low-dose nano-silica can cause granulomas in the liver, and gradually fibrosis, and the accumulation of mast cells in multiple organs (liver, heart, lung). In short, the toxic mechanism of nano-silica presents diverse forms, which requires special attention when evaluating the toxic effects of nano-silica, so as not to omit the relevant effects and cause misjudgment.

Although fumed silica belongs to the category of nano-silica, because fumed silica is usually in the state of agglomerates, the particle size distribution is 10-50um, even if it is fully dispersed in the liquid or solid phase system, the gas phase Silicon oxide also exists in an aggregate state, with a particle size distribution of 100-300 nanometers. It is extremely difficult to disperse fumed silica to the primary particle size.

Research (Zhou F, Liao F, Chen L, et al. The size-dependent genotoxicity and oxidative stress of silica nanoparticles on endothelial cells [J]. Environ Sci Pollut Res Int, 2019, 26(2): 1911-1920.) It shows that when nano-silica is injected into mice through the tail vein, the particle size (10, 30, 50, 70, 100, 300, 1000nm) is negatively correlated with thrombocytopenia, liver damage and lethal toxicity . That is, the larger the particle size, the less the toxicity of nano-silica in the organism. In addition, the larger the particle size, the more difficult it is for nanomaterials to enter the organism. In summary, although nano-silica including fumed silica has certain biological toxicity, due to the relatively large particle size of fumed silica, its biological toxicity is at a relatively low level.