The Synthesis And Properties Of N-halamine-labeled Silica-polyacrylamide Nanoparticles For Antibacterial Ability

The outbreaks of pathogenic microorganisms will bring great harm to human beings, and even endanger the stability of society and the sustainable development of economy. Antimicrobial materials can effectively resist the invasion of pathogenic microorganisms and protect the health of human beings.N-halamine is a new kind of antibacterial agent. It has many unique properties compared with other traditional antibacterial agents, such as effective and wide antibacterial performance, long-term stability, high durability, regenerability and safety to humans and environment. N-halamine compound can be defined as a compound containing one or more nitrogen-halogen（N-X, X can be Cl or Br） covalent bonds that is usually formed by halogenation of imide, amide, or amine group. The antibacterial process is that N-X bonds in this kind of compound will decompose slowly in water and release the oxidation state X+. It is the oxidation state X+ that can kill bacteria and other microorganisms. After killing the bacteria, N-X bond is reduced to N-H bond. After brief rinse by bleach（hypochlorite as the active ingredient）, the N-X bond can be oxidized to N-Cl bond and regain antibacterial properties.Typically, the antibacterial performance of N-halamine-based materials primarily depends on the specific surface area of the material. Thus, nanoscale N-halamine antimicrobial agents can exhibit superior antibacterial properties. SiO₂ nanoparticles have large surface areas, as well as the large number of the unsaturated bond and hydrogen groups that in different states, and with a negative charge, often chosen as the carrier.In this article, we present a facile approach to produce antimicrobial silica@polyacrylamide（SiO₂@PAM） core-shell nanoparticles, which were synthesized via an electrostatic self-assembly method using acyclic N-halamine polymeric polyacrylamide（cationic polyacrylamide and anionic polyacrylamide）. After treatment with bleaching, the amines groups in polymer shell were transformed into N-halamine structures to obtain N-halamine-labeled silica–polyacrylamide core–shell nanoparticles（SiO₂@PAMC）.The main contents are as follows:1. We present a facile approach to produce antimicrobial silica@polyacrylamide（SiO₂@PAM） core-shell nanoparticles. The morphologies, structures, sizes of these as-prepared nanoparticles were characterized by different techniques, such as FE-SEM、TEM、TGA、DSC、UV and FT-IR etc.. We found that SiO₂@PAM nanoparticles had spherical shapes and smooth surfaces without any coagulation and also had obvious core-shell structures.2. And their antibacterial performances against both gram-positive bacteria and gram-negative bacteria were evaluated by agar plates and turbidity assays. We also used antibacterial kinetics test to study long-term stability of SiO₂@PAMC nanoparticles. The SiO₂@PAMC nanoparticles displayed powerful bactericidal capability toward both two model bacteria（E.coli and S.aureus.） and also had long-term stability. We also verify that the smaller the SiO₂ is, the more active it will be.3. The in vitro cytotoxicity of the prepared nanoparticles with varying concentrations was studied using mouse fibroblast cells（L929）. The CCK-8 assay revealed that the SiO₂@PAMC composites possessed a noncytotoxic and had a good biocompatibility.In conclusion, we present a facile approach（Lb L） to produce silica@polyacrylamide（SiO₂@PAMC） core-shell nanoparticles that displayed excellent antibacterial activity against E.coli and S.aureus. We also substantiate the particle size effect on the antibacterial activity and the long-term stability and biocompatibility of the SiO₂@PAMC nanoparticles.