Gold Nanoparticle Translocation Across a Droplet Interface Bilayer via Dark-Field Microscopy

For a wide range of biomedical applications, measuring the transport of metal nanoparticles across a cell membrane is of tremendous interest. Such studies are gaining high importance due to applications, especially in the field of drug delivery using NPs. In this work, we measure the passive transport of arginine-functionalized ultra-small gold nanoparticles (AuNPs) with sizes lower than 3 nm across a planar lipid bilayer formed with the droplet interface bilayer (DiB) technique. The AuNPs transport is monitored using dark-field microscopy, which enables the tracking of AuNPs without the use of fluorescent labeling. The measurements of high numbers of events provide a robust quantitative estimation of AuNP translocation dynamics and energy barrier obtained from the lipid bilayer translocation analysis.  Interestingly, we observed that the arginine number coated onto AuNP and the bilayer packing control the AuNPs translocation accross the lipid bilayer.