Research On Sterilization Mechanism Of Ionic Liquids Based On Molecular Dynamics

The abuse of antibiotics leads to an increase in bacterial resistance,which has become a world problem that cannot be ignored.The development of a new type of antibacterial material with broad-spectrum antibacterial activity,which is difficult to produce drug resistance,green and stable,has become the active research direction of researchers all over the world.As a new type of material,ionic liquids have gradually attracted the attention of scientists due to their unique antibacterial properties.Ionic liquids mainly achieve antibacterial effects through physical destruction,which is often irreversible,and bacteria are difficult to repair themselves,so they will not produce drug resistance.It can be used not only as an antibacterial component to destroy bacterial cell membranes,but also as an auxiliary component and drug combination to help it enter the bacterial interior.In recent years,many papers have reported the application of ionic liquids in antibacterial fields.However,the antibacterial mechanism of ionic liquids,especially their interaction with biofilms,is difficult to study from the molecular scale using traditional experimental observations.This article uses computer simulation technology to elaborate its sterilization mechanism at the molecular level.In the first part of the work,based on the molecular dynamics simulation method,this paper constructed the POPC bilayer system in pure water and added eight kinds of ionic liquids with different carbon chain lengths to study the effect of the carbon chain length of the cation on antibacterial performance.Simulation results show that the ionic liquid clearly shows the trend that Cl^-anion stays in the solution and the cation contacts and inserts into the lipid layer.All chain length cations can be inserted into the lipid layer,and with the increase of carbon chain length,the number of cations inserted into the lipid layer increases,resulting in changes in the shape of the lipid membrane,its compressibility decreases,and its volume expands.However,the long carbon chain induced the formation of micelles in the solution,and the ion concentration at the lipid interface decreased,which weakened the antibacterial properties.At the same time,the too short carbon chain is not conducive to the insertion of cations into the lipid,while long carbon chain can ensure the insertion of cations into the lipid and enhance the membrane disturbance.Cations combine with the lipid layer through electrostatic action and hydrophobic action.Adding electrolytes to the solution may weaken the cytotoxicity of ionic liquids.In the second part,the interaction between ionic liquids with different anionic structures and lipid bilayer was investigated.Based on the molecular dynamics simulation method,three anionic systems with different hydrophobicity（Cl^-,PF6^-and[Tf₂N]^-）were constructed,and the thermodynamic parameters,lipid layer thickness and POPC bimolecular membranes potential of different systems were calculated.The simulation results show that the anionic hydrophobicity has a certain effect on the antibacterial properties of ionic liquids.Water-soluble anions（such as Cl^-）do not interact with lipid membranes,anions with certain hydrophobicity（such as PF₆^-）will gather at the interface of lipid and water and form a film with negative charge,however,anions with strong hydrophobicity[Tf₂N]^-will combine with cations near the interface of lipid and water to form precipitation,and a small part of[Tf₂N]^-will enter into the lipid.In addition,lipid thickness and electrostatic potential energy results are consistent with morphological analysis.The results in this paper provide molecular insights into the bactericidal mechanism of ionic liquids and point out factors that may affect the antibacterial properties of ionic liquids in the structure of anions and cations.It is of certain significance to explore the microstructure and properties of new ionic liquid materials at the micro scale by using computer simulation in the future.