Computer Simulations On The Interactions Between An Amphiphilic Copolymer Bilayer Membrane And A Rigid/soft Nanoparticle

Amphiphilic block copolymers can spontaneously assemble into a variety ofnanostructures in aqueous solution, such as planar bilayers and micelles, etc. Suchnanostructures are significant for many biomedical applications. In this thesis, we studiedthe interactions between some type of rigid/soft nanoparticles and a bilayer membranecomposed of amphiphilic copolymers with molecular dynamics (MD). Herein, the micelles,due to the ability of shape deformation, are viewed as soft nanoparticles in the simulations,while the inorganic nanoparticles are considered as rigid ones.First, the fusion between an amphiphilic copolymer micelle and an amphiphiliccopolymer bilayer membrane is investigated. It is found that the fusion between the micelleand the membrane is influenced by the distance between them as well as the amount ofcopolymer molecules those composing the micelle. When the micelle is small (i.e., theamount of copolymers composing the micelle is low), the factor of distance plays animportant role in governing the fusion between the micelle and the membrane. If they areclose enough, even no fusion occurs; however, with the increase of the distance, themicelle possibly becomes merging into the membrane. When the micelle is bigger, theinfluence of the initial distance weakens. However, when the size of the micelle is furtherincreased, fusion events are only observed when the micelle is close to the membrane.Then, the adhesion of an ultrasmall rigid nanoparticle on an amphiphilic copolymerbilayer membrane is investigated. By using molecular dynamics, we find that both size andshape of an ultrasmall nanoparticle strongly affect its adhesion states on a bilayermembrane (e.g., adhesion, separation or entwined by polymer chains). Interestingly, our simulations show that with the decrease of particle size, the effect of particle shapebecomes even more evident for the adhesion behavior. It is indicated that the competitionbetween nanoparticle-polymer binding and polymer chain deformation, both of which areinfluenced by particle size and shape, determines the final adhesion states of an ultrasmallnanoparticle.