Nanosilver and the bactericidal mechanism its
Silver nanoparticles kill bacteria through 2 mechanisms:
- Mechanism of sterilization through contact with bacteria
Nanosilver: size from 10-100 nanometers (1 nanometer = 1 / billion times compared to 1 meter). Because of its small size, it can attach to and penetrate the cell wall of bacteria.
The reason that silver nanoparticles can attach to and penetrate inside the cell wall is due to the positive charge of Ag + on the surface of silver nanoparticles that create an electrostatic attraction between AgNP and the cell membrane. microbial negative due to the presence of thiol (-SH), carboxyl (COOH-), phosphate (PO43-) and amino groups. Thus, it allows AgNP to attach to the cell membrane. Entering the cell wall of bacteria causes the cell components to leak and cause death.
In addition, bacteria eat continuously, the size of bacteria is about 0.5 – 5 micro meters (5-50 times larger than the size of silver nanoparticles), so sometimes it eats nano silver because it cannot distinguish. where is the food When silver nanoparticles penetrate inside microbial cells, nanosilver is electrically conductive, so it can cause electron exchange reaction with proteins, lipids and DNA. The charge interaction between AgNPs and biological molecules will lead to things going up and down, eventually causing death.
This mechanism of contact killing bacteria in Gram-negative strains is stronger than in Gram-positive bacteria. The reason is that the cell wall structure of Gram-negative bacteria is thinner (about 3-4 nm) while in Gram-positive bacteria, the cell wall is thicker (about 30 nm, 10 times thicker than Gram-negative strains).
List some strains of Gram-negative bacteria that cause diseases such as:
– Acinetobacter (Actinobacillus pleuropneumoniae causes pleurisy, bacteria, Acinetobacter baumannii causes meningitis, blood infection, pneumonia can be resistant to many antibiotics …)
– Escherichia (Escherichia Coli or E.coli is bacteria that cause swelling of the head (swollen eyes, swollen forehead), diarrhea)
– Pseudomonas (Pseudomonas aeruginosa bacteria causes blood infection, respiratory tract infection, urinary tract, pneumonia ..)
– Salmonella (Salmonella choleraesuis and Salmonella typhisuis cause paratyphoid with symptoms of loose fertilizers such as new stage goat manure with diarrhea, cold-eared pigs with snail-spikes)
– Vibrio (V. alginolyticus; V. anguillarum; V. ordalii; V. salmonicida, V. parahaemolyticus, V. harvey, V. vulnificus cause blood infection, red body in shrimp and fish. Vibrio cholerae causes gastrointestinal infection slowly which causes cholera in pigs)
– Hafniaceae (Edwardsiella ictaluri causes liver and kidney disease in pangasius, catfish …)
– Vibrio (V. parahaemolyticus causes acute hepatopancreatic necrosis disease, premature death in shrimp) …
– Aeromonadaceae (Aeromonas hydrophila causes hemorrhagic disease in catfish …)
– Flavobacterium (Flavobacterium columnare causes white-tail disease in catfish) …
Some Gram-positive strains cause disease in such as:
Clostridium (Clostridium perfringens causes enteritis, intestinal toxin infection causes hemorrhage and then death)
Enterococcus (Enterococcus faecalis and E. faecium cause a wide range of infections, including endocarditis, urinary tract infections, prostatitis, intra-abdominal infections, cellulitis, and tracer infections. surgery as well as sepsis.
– Listeria (Listeria monocytogenes bacteria causes septicemia that causes death of newborn piglets, premature birth, digestive disorders, absorption, or meningitis, encephalitis)
– Staphylococcus (Staphylococcus hyicus, Staphylococcus aureus, Staphylococcus saprophyticus cause dermatitis in pigs)
– Streptococcus (Streptococcus bacteria cause meningitis to septicemia, polyphonic inflammation, arthritis, endocarditis, pneumonia, Streptococcus sp causes intestinal hemorrhagic disease in tilapia, rosacea.
– Enterococci (Enterococcus faecalis causes disease on tilapia with signs after 24 hours such as bulging eyes 1 or 2 sides, tail wear, bleeding under fins .. and death within 72 hours).
2. The bactericidal mechanism through the release of nanosilver
The environment is always bacteria, the pH of the environment is usually alkaline, but at the location of the bacteria it is acidic, with oxygen in the water, a reaction will occur:
2 Ag + O2 + 4 ions (H +) -> 2 ions (Ag +) + 2 H2O
Ag + ions will react with the cell wall through thiol (-SH) carboxyl (COOH-), phosphate (PO43-) and amine groups (nitrogen functional groups), thereby causing bacterial death.
When silver nanoparticles enter the bacterial cell, the more enzyme content produced by bacteria, the faster the nanosilver conversion reaction to Ag + ion, the higher the Ag + concentration, the more the The more intense the thiol (-SH) functional group (COOH-), the phosphate (PO43-) and the amine group (the nitrogen-containing functional group) lead to the faster killing of bacteria.
In addition, nano-silver interacts with respiratory chain proteins on the membrane, interrupting intracellular deoxidation and creating reactive oxygen species – free radicals OH, O, H2O2 …).
The US Laboratory of Biotechnology is registered with the EPA as a pesticide, approved as a surface disinfectant, a HVAC disinfectant, and as well as a disinfectant for dental waterways. The company has been given a toxicity rating showing that for the product to be environmentally hazardous, 12,4500,000 gallons of silver nanoscale 32 ppm (equivalent to about 47 million liters of 32 ppm, or 3 million liters 500 ppm and 1.5 million liters 1000 ppm) for hospital disinfection would have to be spilled at the same time. Not even a single barrel or tank can hold enough product at once for the product to be considered hazardous in the event of any spills. The US Biotechnology Laboratory has completed millions of dollars of data
comprehensive, independent data on safety and efficacy on their nano silver products, including but not limited to: cytotoxicity study; studies of injection and ingestion of both high and low levels of silver and both short and long term; also skin sensitivity studies. All studies have concluded that ASAP nano silver products are not toxic to cells, animals or humans. The US EPA has issued an RfD for silver which shows that a normal sized adult can safely consume the equivalent of one ounce of product 10 ppm per day over a lifetime (based on 72 years). The European Commission for the Protection of Health and Consumers has commented after a comprehensive study of silver that metallic silver is safe for consumption in drinks and food and can also be sold in stores. health food products as a supplement. Silver is not a metal that causes heavy metal toxicity as has been reported by many pseudoscientists.