With the rapid development of nanotechnology, more and more nano products have come into our lives. We often see slogans such as nano-coating, nano-materials and nano-technology. And vigorously promote its special nature. Faced with these high-tech products, many people will ask, are nanomaterials really that magical?
Among many nano-materials, due to the ubiquity of silver and its broad-spectrum antibacterial properties, the use of nano-silver has penetrated into all fields of daily consumer goods.
The active group of nano-silver is charged silver ion, which will bring completely different special properties from metallic silver because its size is in the nanometer scale range. The antibacterial effect of nano-silver is greatly enhanced, and its mechanism may be related to its large specific surface area and faster release of silver ions, or to the surface activity of nano-silver. Therefore, stronger antibacterial effect can be obtained by using lower concentration of nano silver. It is precisely because of this powerful antibacterial ability that nano-silver is widely used in all aspects of life.
It is estimated that at least 250 kinds of consumer goods in the world use nano silver. Such as food bags, kitchen utensils, food additives, detergents, disinfectants, furniture, cosmetics, sanitary products, baby products, suitcases, door handles, baby products, animal products, plant products and so on. A market-based study investigated the patents related to nano-silver owned by companies that produce nano-silver related products from 1980 to 20 10. The results show that there are 7422 patent groups for commercial products (1980. 1-206438+00). North Korea, China and the United States are the countries that use silver nanoparticles and related products the most.
At present, a big problem is that when nano-products are added to products, corresponding safety problems will also be introduced, but these safety problems are not conclusive and there is no corresponding mature detection method. In the case that the safety of nanoparticles is not clear, can it be necessary and sufficient to study and demonstrate the safety of these nanomaterials before they are widely used to avoid repeating the same mistakes?
The discussion on the safety of nano-silver has a long history. Some people think that the use of metallic silver has proved that silver is harmless to health for thousands of years. But this view ignores the difference between nano-silver and metallic silver, and nano-silver also has special properties that metallic silver does not have. At present, our understanding of the toxicity of silver nanoparticles is still very limited. Others think that nano-silver may be harmful to human health and the environment.
Although silver has a strong antibacterial effect, it can't distinguish good bacteria from bad bacteria. Under normal circumstances, our human body carries some non-pathogenic bacteria, which is beneficial to our health. For example, skin, as the first line of defense against foreign invasion, plays an irreplaceable protective role in addition to its own barrier function. When using nano-silver products to contact the skin, it will destroy this biological protection system and cause damage to the immune system.
At present, there is no direct evidence of the impact of nano-silver on human health, but we can see the potential harm of silver from some in vitro experiments. Studies have shown that the contact of silver nanoparticles can lead to inflammatory reaction, oxidative stress, genotoxicity (affecting germ cells) and cytotoxicity. Nano-sized silver is more toxic than large-sized silver, which may be due to the increase of specific surface area due to small size. However, whether the toxic effect of nano-silver comes from the small size effect, or from the silver ions released by it, or both, needs to be proved by experiments.
In plastic surgery, coating nano-silver particles on the surface of implants can effectively prevent postoperative infection. However, a recent study shows that 50 nm nano-silver particles can produce high toxic effects on osteoblasts and osteoclasts (two main cells that maintain bone growth and metabolism) under the condition of low effective antibacterial concentration, while 3 micron silver particles have low toxicity, and the concentration of silver ions that play an antibacterial role is 2-4 times higher than the toxic concentration. This may be because the smaller the particle size, the larger the surface area and the more silver ions are released. This will affect the biocompatibility of the implant.
We can also see colloidal silver products for oral use in the market. The National Institutes of Health pointed out that animal studies show that silver will accumulate in the body. The accumulation of colloidal silver in human body will lead to silver deposition. This disease can cause skin, other organs, deep tissues, nails and gums to turn blue-gray. Another side effect of eating colloidal silver is neurotoxicity (such as epilepsy), kidney injury, stomach injury, headache, fatigue and skin irritation. The National Institutes of Health pointed out that many benefits of colloidal silver have no scientific basis. 1999, FDA announced that products without colloidal silver were considered safe and effective.
The use of nano-silver products will also cause potential harm to the environment. For example, the nano-silver washing machine is said to have good sterilization effect. But it also kills normal bacteria. The discharge of nano-silver into sewage will kill normal bacteria in soil and water, which is harmful to soil and water circulation. Therefore, the nano-silver washing machine has been banned from continuing production in Sweden.
The unrestricted use of pesticides will lead to drug resistance, inflammation and imbalance of normal flora in human body. Using cosmetics and sanitary products containing nano-silver can make nano-silver particles pass through skin, mucosa and lungs. The digestive tract enters the human body. Due to the lack of strong evidence of the possible consequences of these phenomena, it is impossible to assess their risks. And it is impossible to know how the normal flora of human skin will be affected.
Materials in contact with food are also gradually using nano-silver materials (such as storage bags, refrigerator coatings, etc.). ), and nano-silver may penetrate into food, but the data about its possible harm are not sufficient. There is no reliable data to analyze the relationship between the quantity of nano-silver products and the environment. Silver is considered as a toxic metal, which can accumulate in the human body, mainly damaging the stomach and liver, and also having neurotoxicity. The World Health Organization has declared that silver is a toxic substance, and the US Environmental Protection Agency believes that silver, as a bactericide, has a destructive effect on soil organic matter and water system.
Nanotechnology has been given great hope and made new breakthroughs in medicine, energy, electronics, materials and other fields. Because nanomaterials have different characteristics from large-scale materials, the unique advantages of nanotechnology are undeniable. Nano-materials show advantages because of their characteristics, but also hide the potential harm to health and environment.
However, while any new technology exerts its great advantages, it is bound to be accompanied by potential dangers, which are not unique to nanotechnology. Usually, such as electricity, daily cleaning supplies, gasoline and medical X-rays, the more I know about the risks of a technology, the more information I have to successfully use this technology and fully realize its benefits.