High‐Throughput Microfluidic‐Mediated Assembly of Layer‐By‐Layer Nanoparticles

Surface modification of nanoparticles (NPs) via the layer-by-layer (LbL) technique is a promising approach to generate targeted drug delivery vehicles. LbL-NPs have been successfully used in preclinical models for controlled drug release, tumor and immune cell targeting, improved pharmacokinetics and biodistribution, and controlling cellular trafficking and uptake mechanisms. A simple and scalable synthesis method for LbL-NPs that can be adapted for clinical translation is of great interest. Here we present a new method of polymer deposition onto NPs enabled through microfluidic (MCF) mixing. NPs are mixed with polyelectrolytes using commercially available bifurcating mixer MCF cartridges. In addition to increased process robustness, MCF allows for LbL electrostatic assembly using titrated polymer-to-NP weight equivalent ratios where no excess polymer is required to achieve a given LbL layering. Under such conditions, no time-consuming purification is needed, greatly increasing LbL-NP throughput and avoiding the loss of NPs during purification. We demonstrate the utility of this system using IL-12-loaded liposomal NPs which show equivalent efficacy in vitro and in vivo to LbL-NPs generated via traditional lab-scale batch-wise polymer adsorption and tangential flow filtration purification. Moreover, we show that MCF can assemble LbL films of various chemistries and on various NP core substrates.