Functionalized Solid-Sphere PEG-b-PCL Nanoparticles to Target Brain Capillary Endothelial Cells In Vitro

Nanoparticles are increasingly used to implement drug targeting strategies. In the present study, solid-sphere nanoparticles (SNPs) made of poly(ethylene glycol)-b-poly(ε-caprolactone) (PEG-b-PCL) were covalently linked to a monoclonal antibody (83-14 mAb) targeted against the human insulin receptor that is highly expressed on human brain microvascular endothelial cells. Resulting targeted SNPs were characterized using transmission electron microscopy (TEM), cryo-TEM, dynamic light scattering, and fluorescence correlation spectroscopy. The critical aggregation concentration was determined using a fluorescence approach. Interaction with a well-characterized human in vitro model of the blood-brain barrier (hCMEC/D3) was analysed using an array of methods (flow cytometry, confocal laser scanning microscopy, and TEM). The toxicity on hCMEC/D3 cells and in addition on the human liver cell line HepG2 was assessed using the MTT assay. SNPs with a diameter of 80 nm and a homogeneous size distribution were obtained. Successful conjugation of 83-14 mAb using a heterobifunctional linker resulted in 5-6 molecules of fluorescently labeled 83-14 mAb per SNP. Functionalized SNPs were taken up by hCMEC/D3 cells efficiently without showing a significant toxic effect on cells of the blood-brain barrier and HepG2 cells. These results indicate that functionalized PEG-b-PCL SNPs are a promising candidate to deliver drugs to the CNS.