Investigating the diffusion of nanoparticles on lipid bilayer is important in understanding many biological processes on cell membrane. Molecules and nanoparticles are observed to diffuse laterally on lipid bilayers. Conventionally, this diffusion is believed to be confined in the two-dimension (2D) plane, i.e., 2D planar diffusion. Recently, evidence shows that desorption of the nano-objects may be involved in the process and play an important role in their lateral movement, i.e., desorption assisted diffusion. With conventional 2D single particle tracking (SPT) techniques, the diffusion detail in z direction is missing thus it is challenging to differentiate these different diffusion modes. Using cholera toxin (CTxB) as the ligand, we studied particle diffusion on ganglioside GM1-containing bilipid. We successfully recovered the trajectory of the particle diffusion on solid supported lipid bilayer in the whole 3D space. Different diffusion modes under various conditions were observed. At physiological pHs, ligand-tagged nanoparticles showed confined diffusion within “domains”, and “hopping” between different domains. The transport of the particle between domains can involve two different modes: the in-plane mode during which the particle stayed within the lipid layer, and the out-of-plane modes, during which the particle desorbed from the lipid bilayer and moved in the solution before it landed on the lipid bilayer again. At an elevated pH, the particles showed more domainized diffusion, suggesting lipid phase segregation is favored under this condition. These observations were not made using 2D SPT in the past and will help us understand how particle and lipid bilayer interact with each other.<br/> <br/>

3D single particle tracking discloses diffusion modes on solid supported lipid bilayer

256th National Meeting (2018)

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