Peptide-Functionalized Layer-by-Layer Nanoparticles with Improved Blood Brain Barrier Permeability for Glioblastoma Treatment

Glioblastoma is an aggressive brain tumor that accounts for almost 50% of all brain and central nervous system tumors, but the current standard of care gives a median survival of only 15 months. The greatest obstacle in the treatment of glioblastomas is the blood-brain barrier (BBB), the endothelial cells that line the vessels of the brain and are stitched together into a barrier by tight junction complexes. The BBB is designed to prevent pathogens from entering the brain, but its inability to distinguish between harmful substances and therapeutics leads to a fundamental problem in brain drug delivery. One approach to overcoming this barrier is encapsulating drugs in nanoparticles whose surfaces are engineered (usually, with the addition of ligands) to promote binding to various receptors of the BBB, thus triggering transcytosis and allowing the nanoparticle and its drug contents to cross the BBB.<br/><br/>Previous research has shown that electrostatic absorption (as opposed to covalent functionalization) is a quick and effective method for attaching cationic, tumor-penetrating peptides to anionic nanoparticles synthesized through an iterative layer-by-layer (LbL) approach [1]. Here, we demonstrate that LbL nanoparticles functionalized with BBB-targeting peptides, including Angiopep-2 and RAP12, can penetrate the BBB to deliver their contents to the brain. We probe how different characteristics of the nanoparticles (e.g. polyanion used to present surface chemistry in the outermost layer) and peptides (e.g. charge, size) affect stability of the LbL nanoparticles in a variety of salt and temperature conditions. Particles that exhibited the highest stability were screened through cell culture and mouse models of the BBB, and certain peptides lead to increased uptake both <i>in vitro</i> and <i>in vivo </i>in the mouse brain. Ongoing work includes molecular dynamics simulations to understand interactions between the BBB-targeting peptides and the outermost polymeric layer of the nanoparticles, with a focus on matching <i>in silico</i>conformation results with outcomes from biological experiments to enable future prediction of the effectiveness of various peptide-outer layer combinations. <br/><br/>1. N. Boehnke, K.J. Dolph, V.M. Juarez, J.M. Lanoha, and P.T. Hammond, Bioconjug. Chem. 31(9) 2211-2219 (2020)