Ultrathin Silicon Membranes for In Situ Optical Analysis of Nanoparticle Translocation across a Human Blood-Brain Barrier Model

Here we present a blood-brain barrier (BBB) model that enables high-resolution imaging of nanoparticle (NP) interactions with endothelial cells and the capture of rare NP translocation events. The enabling technology is an ultrathin silicon nitride (SiN) membrane (0.5 µm pore size, 20% porosity, 400 nm thickness) integrated into a dual chamber platform that facilitates imaging at low working distances (~50 µm). The platform, the µSiM-BBB (microfluidic Silicon Membrane-BBB), features human brain endothelial cells and primary astrocytes grown on opposite sides of the membrane. The human brain endothelial cells form tight junctions on the ultrathin membranes and exhibit a significantly higher resistance to FITC-dextran diffusion than commercial membranes. The enhanced optical properties of the SiN membrane allow for high-resolution live-cell imaging of three types of NPs, namely 40 nm PS-COOH, 100 nm PS-COOH, and apolipoprotein E (ApoE)-conjugated 100 nm SiO2, interacting with the BBB. Despite the excellent ...