Research On The Nanosilver Antifouling Preparation And Inhibition Of The Marine Bacteria Adhesion

Marine fouling organisms are those animals, plants and microorganism who live on the surface of ships and other facilities. Marine fouling organisms could fouling the surface of materials and lead to biocorrosion which are ordinary in the marine. Biofouling and biocorrosion interact each other and lead to reduction of the performance and lifetime of facilities. Biofouling was caused by biofilm; one effective method to solve biofouling is inhibition of biofilm occurrence.This research use nanosilver technology to resolve the problem of marine bacteria adhesion, according to the bactericidal ability of different diameter nanosilver particles, nanosilver deposited on the surface of the Si O2/PDA spheres(silica/polydopamine/silver nanoparticles) and nanosilver encapsulated in mesoporous Si O2 NPs(Ag-MSN) were designed and preparated. The bactericidal mechanisms and ability of these two kinds of particles was studied and discussed, especially two structures, affection on bactericidal mechanisms and ability. We finally arrived at the conclusions as following:(1) Xylene was used as solvent and stabilizer, silver nitrate was deoxidated by oleylamine. The preparate nanosilver diameter was approximately 20 nm, 50 nm and 80 nm, which distribute uniformly. Bactericidal experiment on Vibrio Natriegens(Gram negative) and Bacillus subtilis(Gram positive) indicated that 50 nm nanosilver had the highest bactericidal performance, 20 nm particles ranked secondly. 80 nm particles could not penatrate into bacteria, 20 nm could penetrate in bacteria, but it was oxidized faster than 50 nm. Both two reasons lead to 50 nm particles had the best effection. The same diameter particles bacteriostasis was concentration dependent. V. Natriegens(Gram negative) was more sensitive than B. subtilis(Gram positive), which was caused by the peptidoglycan layer which could protect the bacteria to a certain degree.(2) On alkaline condition, TEOS was used as source of silicon dioxide, isopropyl alcohol was used as solvent, ammonium hydroxide was used as catalyst, 200~300nm silicon dioxide particles were prepared. Prepared particles carrier took nanosilver particles which were revivified by poly dopamine, which had core-shell-satellite construction. The thickness of poly dopamine was 30 nm, the diameter of nanosilver was about 50 nm. Antibacterial test indicated that the minimal inhibitory concentration(MIC) on V. Natriegens and B. subtilis was 0.38mg/m L and 0.54mg/m L. Growth curve test showed that these particles had a significant inhibition effect on the two bacterial strains, it had a better effect during the first three days. ROS test and DNA damage test showed that ROS could damage DNA and affect DNA biological function. Transmission electron microscope(TEM) test indicated that nanosilver fall off from silicon dioxide could enter into V. Natriegens and bring damage on interior, but it did not happen on B. subtilis, which explain that the bactericidal effect come from ROS and silver ions penetrated the cytomembrane. The common bactericidal effect on V. Natriegens come from nanosilver penetration which could produce ROS, the outside ROS penetration and silver ions. After 7 days immersion in artificial culture bacterium solution, the sample card which coated with silica/polydopamine/silver nanoparticles can not be seen any bacterial adhesions show it has a good effect on bacterial adhesion.(3) Cetyl trimethyl ammonium bromide was used as template and tetraethyl orthosilicate was transformed to nano silicon dioxide particles. Then sodium hydroxide was used as basic catalyst, silver nitrate was revivified to nanosilver, nanosilver encapsulated in mesoporous Si O2(Ag-MSN) was prepared which has a core-shell composite particles and about 250 nm diameter, nanosilver diameter was 50 nm approximately. Antibacterial test indicated that the MIC of Ag-MSN on V. Natriegens and B. subtilis was 0.58mg/m L and 0.68mg/m L. Growth curve test showed that these particles had a significant inhibition effect on the two bacterial strains, it had a better effect during the last five days. ROS test and DNA damage test showed that ROS could damage DNA and affect DNA biological function. TEM test showed that there was no Ag-MSN in both strains, it indicated that the antibacterial effect come form outside ROS which could bring oxidative damage and silver ions. Without peptidoglycan layer, V. Natriegens was more sensitive to this particle. After 7 days immersion in artificial culture bacterium solution, the sample card which coated with Ag-MSN nanoparticles can not be seen any bacterial adhesions show it has a good effect on bacterial adhesion. Antibacterial test indicated Ag-MSN struction slowed down the oxidation of nanosilver, which could keep longer production and delayed release of ROS.