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Silver nanoparticle exerts antibacterial effect by affecting the living environment of bacteria

wallpapers News 2021-01-08
In the solution, under the synergistic effect of oxygen and protons, silver nanoparticle releases silver ions or is oxidized by oxygen to form nano-silver oxide, and then release silver ions to exert antibacterial effects.
 
Some studies believe that silver nanoparticle itself has no effect on bacteria, and the inhibitory effect stems from the release of silver ions and strictly depends on the oxygen concentration.
 
Both silver nanoparticle and silver oxide particles show strong antibacterial properties under aerobic conditions. However, the metabolism of bacteria such as aerobic respiration greatly reduces the oxygen content, resulting in a reduction in the concentration of silver ions and reducing the antibacterial ability. The reduction of oxygen concentration in the environment has a huge impact on aerobic bacteria, directly inhibiting or even killing bacteria.
 
Silver nanoparticle exerts antibacterial effect by destroying the cell wall
Silver ions and silver nanoparticles carry positive charges through electrostatic attraction between negatively charged bacterial proteins and are adsorbed on the cell membrane. Due to its high surface energy and dispersibility, chemical interactions between silver nanoparticles and cell walls can occur and destroy the integrity of the cell walls. This is especially evident in the electron-rich part of the cell wall. Causes the loss of normal cell wall functions, such as nutrient penetration.
 
At the same time, silver nanoparticle and silver ions act as peroxidation inducers of the membrane, interacting with certain proteins and phospholipids to induce membrane damage or decomposition.
 
Silver nanoparticle exerts antibacterial effect by inhibiting DNA replication
Silver nanoparticle penetrates the cell wall and enters the bacterial body through the action of membrane proteins and lipids (including permeability changes and perforations, etc.). silver nanoparticle enters bacteria and aggregates to form low molecular weight aggregates, and the cell wall is separated from the cell membrane, so DNA can be aggregated and concentrated to avoid silver nanoparticle damage. DNA stays in the replication interval and cannot complete the replication process. Or by blocking the electron transport system in bacteria to enhance the stability of bacterial DNA, the DNA cannot untie the double helix, loses the ability to replicate, and the speed of bacterial division is reduced.
 
Silver nanoparticle exerts antibacterial effect by inhibiting enzyme respiration
Many studies believe that silver nanoparticle inhibits bacterial respiration as another antibacterial method, including reducing the oxygen concentration in bacteria in vivo and in vitro and directly acting on enzymes related to respiration and ATP production.
 
The process of silver nanoparticle dissolving and releasing silver ions consumes oxygen, reduces the solubility of oxygen in the bacterial environment and the bacterial body, and effectively inhibits the respiration of bacteria.
 
Silver nanoparticle exerts an antibacterial effect by inhibiting the activity of other enzymes
When silver nanoparticle enters the cell, due to electrostatic attraction, it first binds to the negatively charged enzymes, proteome or organelles and lipids in the cell. In addition, it combines with the electron donors (L-cysteine, etc.) in the enzyme, such as sulfur, oxygen and hydrogen, and even replaces the metal ions in the enzyme, resulting in inactivation or even inactivation of the enzyme activity. In wound adjuvants, silver nanoparticle inhibits the degradation of growth factors by inhibiting matrix metalloproteinases and improves wound healing speed.
 
In addition, silver ions and silver nanoparticles combine with amino acid residues (cysteine ​​sulfide), amino, imidazole, phosphoric acid and carboxyl groups in functional proteins to change the three-dimensional conformation of the enzyme, resulting in irreversible protein and The normal metabolism of bacteria cannot proceed.
 
In summary, silver nanoparticle is partially dissolved in the solution to release silver ions. silver nanoparticle and silver ions are fixed on the negatively charged functional groups on the bacterial cell wall. Functional proteins are affected by silver, and the structure of bacterial cell walls and cell membranes will also change. Dysfunctions, especially changes in membrane permeability, enter the cytoplasm and cause the loss of bacterial nutrients. Silver destroys the DNA structure in the cytoplasm, inhibits its replication and respiratory chain enzymes and other related activities, and ultimately leads to bacterial inactivation. 

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