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Nano-gold is a new breakthrough in biomedical applications

2019-04-25
Nanomaterials are new materials with different properties from microscopic atoms, molecules and macroscopic materials. They have been widely used in electronics, chemical industry, aerospace and other industries.Nanogold is a small particle with a diameter of 1-100 nm and usually exists in aqueous solution as a colloid. Its properties mainly depend on the size and surface characteristics of the particle. When the size is reduced to the nanometer range, it will show surface effect, quantum effect, macroscopic quantum tunneling effect and other characteristics.Nano-gold has attracted extensive attention in chemical industry, environment, optics, electronics, biological medicine and other fields due to its unique photoelectric and catalytic properties.
 
The preparation methods of gold nanoparticles include physical method, chemical method and biological method.
 
Physical synthesis
Gold is directly converted into nanoparticles through various dispersion technologies, mainly including gas phase method, liquid phase method, high-energy mechanical ball grinding method, etc. This method has high requirements for instruments and equipment, high production costs, and wide particle size distribution, which greatly limits the application of this method.
Chemical synthesis
Chemical methods mainly include REDOX method, microwave method, electrochemical method, microemulsion method, etc. This method has the advantages of controllable particle size and high production efficiency, and is the main way to produce nano gold materials.
Biosynthesis
Microbial reduction preparation methods can be divided into intracellular and extracellular reduction.In the extracellular reduction of gold nanoparticles, the bioactive substances secreted by microorganisms include proteins, reducing sugars, and reduced glutathione, etc., to enrich and reduce ions and form typical nanoparticles. Bioactive substances also play an important role in the stabilization of gold nanoparticles.The intracellular synthesis of gold nanoparticles is a very complex biochemical process.

Application of nano-gold in biomedical field
Gold nanoparticles have a strong adsorption function on biological molecules and can bind to DNA, proteins, enzymes, hormones and other non-covalent bonds. Therefore, they have become very useful tools in basic biochemical research and experiments.Adsorption mechanism of gold nanoparticles surface negative charge, and modify material surface groups, DNA on the surface of negative charge, because of the electrostatic adsorption to form a strong combination, and will not make biological molecules degeneration after adsorption, due to the characteristics of the gold particles with high electron density, when these markers in the corresponding ligands in a large number of gather, can use instrument testing related biological, chemical, and converts it into usable signal according to certain rule (including electric signals and optical signals, etc.), which is applied to the qualitative or semi-quantitative rapid immune detection method.
The application of nanoparticles to DNA electrochemical biosensors is mainly used to improve the sensitivity and stability of the sensors.Gold nanoparticles can increase the specific surface area of electrochemical DNA biosensor electrode, thus increasing the fixed number of probe DNA.And the detection signal of the sensor can be amplified by accelerating electronic transmission.
 
Professor Zhao et al. modified gold nanoparticles by using quantum dots instead of common fluorescent dyes. When the probe identified the miRNA of tumor cells, the fluorescence signal of the quenched quantum dots was recovered and enhanced, so as to characterize the information of miRNA.Gold nanoparticles modified with quantum dots not only detect miRNA in Hela cells, but also detect the distribution of miRNA in tumor mice.Nanogold can be used as a tumor probe to detect intracellular and extracellular tumor markers with high sensitivity and specificity.