At present, New Coronavirus has ravaged China. As of 24 February 7th, 31 provinces (autonomous regions and municipalities directly under the central government) and the Xinjiang production and Construction Corps reported a total of 31774 cases, which far exceeded the number of SARS diagnosed in 2003. In the past, several difficult viruses (such as HIV, HBV, PIV, etc.) have not yet been broken. New variants of the virus, such as SARS coronavirus, avian influenza virus and influenza a H1N1 virus, are now seriously affecting human health in the face of mankind. Many viruses, such as influenza virus, SARS coronavirus, avian influenza virus and human immunodeficiency virus infection, are difficult to control. The main reason is that these viruses are infected on the mucosal surface, weak antigenicity and prone to antigen mutation and drug resistance mutation, which leads to poor clinical prevention and treatment of these viruses.
Detection, prevention and treatment of infectious diseases is a difficult problem in medical field. At present, vaccine control is the main control of viral infectious diseases, but there is no effective treatment strategy for the established viral infection. But with the progress of medical research, researchers found that there are some antiviral materials in the world, and some of them have been used in clinic.
calcium phosphate
Biominerals can be divided into calcified biominerals and non calcified biominerals according to their composition. Calcified minerals mainly include calcium carbonate (calcite, aragonite, nepheline and amorphous calcium carbonate) and calcium phosphate (hydroxyapatite, octacalcium phosphate, etc.). Calcium phosphate is a common biological mineral in higher mammals. Calcium phosphate in organisms is basically the same as that in natural minerals. It is represented by apatite crystals and is the main inorganic component of hard tissues such as bone and teeth in vertebrates. Similarly, pathological calcification also exists in mammals, and its main component is calcium phosphate. Because of the similarity of chemical structure between calcium phosphate and bioinorganic calcified tissue, this kind of material has good biocompatibility, so it is widely used to develop medical biomaterials, which is the focus of biomaterial research.
Calcium phosphate (CAPS) is the main inorganic component of bone and teeth, and plays an important role in people's life. The biomedical research of caps materials developed rapidly in the 1970s, and has been widely used in the field of orthopedics and dentistry; It can be used as artificial bone graft substitute in the form of thin coating on metal implant.
The preparation methods of calcium phosphate mainly include gel sol method and coprecipitation method. Emulsion method, hydrothermal method, inorganic chemical method, ultrasonic method, microwave technology, template method, emulsion hydrothermal method and microwave hydrothermal method. Through these methods, calcium phosphate with different structures and morphologies can be prepared, including needle like, spherical, fibrous, porous, rod like, hollow spherical, layered and flower like structures.
Gold nanoparticles
Gold nanoparticles (AuNPs) have become an ideal delivery system for drug delivery and release in different types of cell systems. This ideal delivery performance is closely related to many characteristics of gold nanoparticles（ 1) In gold nanoparticles, gold core is completely natural, nontoxic and biocompatible, which provides an ideal starting point for the construction of carrier（ 2) Gold nanoparticles have a wide range of sizes (1-150 nm) and can be easily dispersed and controlled. Size and dispersion are the key factors of drug delivery system（ 3) Gold nanoparticles have size and morphology dependent photoelectric effect（ 4) Gold nanoparticles have higher surface area, which is more conducive to drug loading（ 5) The highly tunable and multivalent surface structure of gold nanoparticles provides a variety of possibilities for covalent or covalent coupling of multiple therapeutic drugs or biomacromolecules to the particle surface.
At present, the synthesis of gold nanoparticles is mainly based on the reduction of chloroauric acid in the presence of stabilizers. The most common method is to use sodium citrate reduction synthesis method, including the use of citrate to reduce chloroauric acid nucleation. Another method is to extract medicinal plants with formaldehyde as reducing agent to produce "green" or environment-friendly nanoparticles. Seed mediated growth of gold nanoparticles is also a common method to accurately control the size and shape of gold nanoparticles. In this method, small size gold nanoparticles are synthesized firstly, and then large size gold nanoparticles are prepared by using small size gold nanoparticles as seeds (nucleation centers).
Silver nanomaterials
Among many antimicrobial materials, nano silver has been studied most thoroughly and has been applied in medical treatment. The antibacterial properties of silver have been known in ancient times. Metal silver, silver nitrate and silver sulfadiazine cups are used in the treatment of burn wounds and the control of dental bacterial diseases.
Among many metal and its oxide nanoparticles, silver nanoparticles have the best antibacterial effect and the most extensive research. Many researchers have confirmed that silver nanoparticles can effectively inhibit bacteria, viruses and fungi, especially the growth of antibiotic resistant strains.
The antibacterial effect of silver nanoparticles with different sizes is different, and generally the antibacterial effect decreases with the increase of particle size. In addition to silver nanoparticles, other shapes of silver nanomaterials, such as silver nanowires, silver nanorods and silver nanohorns, also have antibacterial effects, but their antibacterial effects are different.
In addition, nano silver can inhibit the growth of a variety of pathogens in Clinical Urology, orthopedics, oral surgery, dermatology and burn surgery. Many wound dressings, medical device coatings and masks contain nano silver.
纳米材料抗菌机制
As a potential antibacterial and antiviral material in the future, the safe and effective application of nano silver in human body is particularly important. We should not only study the toxic and side effects of nano silver at the cellular level or animal level, but also conduct scientific research in human body to prove that nano silver has high antiviral effect and is harmless to human body.
Molybdenum oxide nanomaterials
There are few researches on the application of molybdenum oxide nanomaterials in biomedicine. With the development of nano medical science, some new functions of nano molybdenum oxide are gradually explored, especially in the biomedical field. For example, molybdenum oxide nanodisks with specific surface morphology can be used for antibacterial applications; Two dimensional layered molybdenum oxide nanosheets have been widely used in biomedical fields such as photoacoustic diagnosis and treatment, tumor photothermal removal and so on; Molybdenum trioxide hollow nanospheres have great potential in drug loading and delivery; Molybdenum trioxide nanoparticles with the size of 2 nm can be used as biological enzyme catalyst to realize sulfite oxidase activity by electron transfer.
Other metal nanomaterials
Gold, copper, zinc oxide, titanium dioxide and other nanoparticles have antibacterial and antiviral activities. Heavy metals such as silver, copper, lead and mercury can react with sulfhydryl groups in proteins, or replace metal ions in enzymes to inactivate most enzymes. Therefore, heavy metal ions have broad-spectrum antibacterial and antiviral activities.
It is worth noting that although metal nanomaterials have excellent antibacterial and antiviral activities, their toxic mechanism is still controversial. The release of metal ions will pose a potential threat to the environment and human body.
Carbon nanomaterials -- fullerenes and their derivatives
Lyon et al. Found that no reactive oxygen species were detected in E. coli treated with C60, indicating that the antibacterial mechanism of C60 may not depend on the reactive oxygen species pathway (lyonel 2008). There are also studies that the antibacterial effect of fullerenes on prokaryotic cells is mediated by lipid peroxidation of cell membrane (sayesetal 2005). On the other hand, fullerenes have antiviral effect.
Friedman et al. Found that C60 can inhibit human immunodeficiency virus protease (HIV), and HIVp is the main target of anti-virus. Inhibition of HIVp can terminate the life cycle of HIV.
Antonio et al combined fullerenes with many monosaccharides to synthesize a large spherical structure, which has an effective inhibitory effect on Ebola virus. However, the antibacterial mechanism of fullerenes is still controversial. Some scholars believe that fullerenes can cause photocatalysis to produce reactive oxygen species in eukaryotic cells.
Carbon nanotubes
Carbon nanotubes (CNTs) are one-dimensional tubular nanomaterials, which are made of graphene sheets coiled around the central axis. According to the number of cylinder layers, they can be divided into single-walled carbon nanotubes (SWCNTs) and multi walled carbon nanotubes (MWCNTs). At present, there are many reports about the antibacterial properties of CNTs. SWCNTs have better antibacterial effect on bacteria and fungi, and the antibacterial effect of SWCNTs is better than MWCNTs.
Upadhyayla et al. Proved that SWCNTs have very high adsorption capacity. The adsorption capacity of SWCNTs to Bacillus subtilis spores is 27-37 times higher than that of activated carbon and nano ceramics. The high adsorption capacity of SWCNTs mainly depends on their fibrous shape, large aspect ratio and large specific surface area. At the same time, the adsorption of CNTs on bacteria was very fast. The adsorption kinetics of swcmts on Bacillus subtilis, Staphylococcus aureus and Escherichia coli were tested. The results showed that 95% of the bacteria could be adsorbed on the surface of SWCNTs in 5-30 minutes.
The antibacterial properties of CNTs are influenced by many factors. SWCNTs with smaller diameter are conducive to partition and more easily penetrate into cell wall, while their larger surface area is more conducive to contact and reaction with cell surface. Therefore, the antibacterial properties of smcnts are better than those of MWCNTs.
Anti Bacteria Mechanism of Graphene
Graphene oxide
In 2004, British scientists discovered a new type of two-dimensional atomic crystal graphene, which is composed of carbon atoms connected by SP2 hybrid monolayer. Its basic structural unit is the most stable benzene six membered ring in organic materials, and it is the most ideal two-dimensional nano material at present.
As a derivative of graphene, graphene oxide is the exfoliated product of graphene oxide. Through plaque formation test, indirect immunofluorescence and Western blot, researchers found that graphene oxide nanomaterials have good antiviral effect on pseudorabies virus (DNA virus) and porcine epidemic diarrhea virus (RNA virus), The inhibitory effect was time and dose-dependent. In addition, the researchers also found that two-dimensional flake nano materials such as molybdenum disulfide and tungsten disulfide also had good antiviral effect, but the inhibition effect was lower than that of graphene oxide.
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