Delivery of monoclonal antibodies to the brain: the impact of nanocarrier structure

Monoclonal antibodies (mAbs) are promising therapeutic agents for neurological disorders due to their high specificity. However, their clinical application is significantly hindered by their poor transport across the blood-brain barrier (BBB) and their limited diffusion within the brain parenchyma. While significant efforts have been oriented to tackle the first barrier, the challenge of efficient brain diffusion remains largely underexplored. To address this, we have developed and evaluated two structurally distinct nanosystems for mAb delivery to the brain: PEGylated polyglutamic acid nanocapsules (PGA-PEG NCs) and PGAC14-based nanoassemblies (PGAC14 NAs). Both formulations encapsulated efficiently the model mAb bevacizumab (BVZ) while they exhibited different physicochemical properties. Namely, PGA-PEG NCs displayed a size of 80 nm and a neutral zeta potential, whereas PGAC14 NAs featured an ultra-small size of 40 nm and a negative surface charge. After assessing their diffusion capacity using immunofluorescence, we concluded that PGAC14 NAs exhibited the highest brain diffusion together with a favorable neuroinflammatory profile. This was likely driven by their small size and negative charge, along with a selective ability to interact with and deliver BVZ intracellularly to neuronal cells upon intraparenchymal administration. These findings provide key insights into optimizing nanocarrier design for improved mAb delivery to the brain.