Silver nanoparticles refer to particles consisting of silver atoms, and their particle size is usually in the range of 1 to 100 nm. The antimony properties of the bulk of the silver material surface are well known, and the mechanism is that the silver atoms on the surface of the material can be slowly oxidized by the oxygen in the environment to release free silver ions (Ag +), which pass through the walls of the bacteria Mercapto binding, blocking the respiratory chain of bacteria, and ultimately kill the bacteria attached to the surface of the material. For bulk silver materials, the oxidation process is extremely slow, the number and rate of silver ions released is also very low.
As with the bulk silver material, the silver nano-surface is oxidized to release free silver ions. However, due to the small size effect and surface effect of the nanoparticles, as the particle size decreases, the number of surface atoms of the silver nanometer The number of atoms increases rapidly, resulting in a significant increase in the rate of release of silver ions; at the same time, due to the large number of particles released on the surface of silver ions, and the particle size is smaller than the virus, silver nano can be through its surface silver ion pair Cell membrane caused by direct damage and into a variety of cells, causing apoptosis or necrosis. Because of the above characteristics, the bactericidal effect of silver nanoparticles is significantly higher than that of silver ions. However, at the same time, silver nanoparticles enter the cells and remain in them, resulting in local high concentration of silver ion distribution, causing clear toxicity and damage to cells, tissues and organs.
The cytotoxic mechanisms of silver nanoparticles mainly include the following aspects
(1) Both silver nanometer itself and its surface silver ions can act on the membrane protein membrane membrane, activation of signal transduction pathway, inhibition of cell proliferation.
(2) through the particle surface of the high concentration of silver ions on the cell membrane oxidation caused by changes in cell membrane permeability, leading to calcium influx and overload, causing oxidative stress and mitochondrial membrane changes;
(3) silver nanoparticles distributed in the cytoplasm cause local high concentration of silver ions released by the role of mitochondria caused by damage to the respiratory chain function, resulting in ROS production, causing oxidative stress and ATP synthesis disorders, leading to DNA damage.
(4) cytoplasmic silver nanoparticles cause cell cycle arrest, causing apoptosis.
(5) silver nano-adsorption of protein molecules caused by a variety of structural changes in the protein, such as inhibition of brain and muscle cells within the creatine kinase activity.
(6) due to the cytoplasm of silver nano-sustained release of silver ions, resulting in DNA damage caused by it can not be completely repaired.
A large number of studies have confirmed that silver can cause a significant increase in the level of silver in various organs and tissues, and accumulate for several months, regardless of the exposure pathways; where the liver and spleen accumulate the most, followed by the kidney Resulting in significant liver, nephrotoxicity and immunotoxicity. Second, silver nanoparticles can span a wide range of biological barriers, including blood brain, blood testis, placenta, intestinal mucosa, etc., resulting in clear central nervous system toxicity, reproductive system toxicity and genetic toxicity.
Therefore, in the consideration of the application of silver nano-ingredients research and development of medical supplies, need to fully understand the silver nano-cytotoxicity, and its clinical application of the necessity, safety and effectiveness, taking full account of the impact of products on public health.