Amphiphilic Polymeric Nanoparticles Modified with a Protease-Resistant Peptide Shuttle for the Delivery of SN-38 in Diffuse Intrinsic Pontine Glioma

Diffuse intrinsic pontine glioma (DIPG) is a chemo-resistant, incurable pediatric tumor of the central nervous system (CNS). The blood–brain barrier (BBB) remains intact in the course of the disease, preventing drugs from entering the brain and resulting in therapeutic failure. The topoisomerase I inhibitor SN-38 shows strong anticancer activity in a patient-derived DIPG cell line in vitro, though a low CNS bioavailability and anti-DIPG efficacy in vivo. In this work, we produced SN-38-loaded polymeric nanoparticles of an amphiphilic chitosan (CS)-g-poly(methyl methacrylate)-poly(acrylic acid) copolymer that were surface-modified with a peptide shuttle that improves transport across the BBB. Drug-loaded nanoparticles displayed a size of ∼200 nm (intensity distribution) and a ζ-potential of +16 mV. The cytocompatibility and endocytosis assayed in DIPG cells (both attached and in suspension) indicated that the nanoparticles are compatible and mainly internalized by clathrin-mediated endocytosis and that the anticancer activity of SN-38 is preserved after nanoencapsulation. In addition, a tandem permeability/anticancer activity study utilizing a coculture model of BBB endothelial cells and DIPG cell spheroids demonstrated that the modified nanoparticles cross a BBB endothelial cell monolayer to a higher extent than the unmodified counterparts and are taken up by DIPG cells. After 72 h of exposure, both SN-38-loaded nanoparticles killed ∼84-88% of the DIPG cells in suspension, indicating that they reach a concentration above the inhibitory concentration 50 of the drug. Finally, the brain accumulation of the drug-loaded nanoparticles upon intravenous injection to Hsd:ICR mice was preliminarily characterized by light sheet fluorescence microscopy. As opposed to unmodified SN-38-loaded nanoparticles, the modified counterparts bind the brain blood vessels and accumulate in the cerebral parenchyma to a large extent. These results confirm the potential of this nanotechnology platform to deliver anticancer agents to the brain in DIPG and other brain tumors with fully conserved BBB.