Binding, Transcytosis and Biodistribution of Anti-PECAM-1 Iron Oxide Nanoparticles for Brain-Targeted Delivery

Efstathios Karathanasis,Mo Dan,Thomas D Dziubla,David B Cochran,Robert A Yokel

doi:10.1371/journal.pone.0081051

Abstract

ObjectiveCharacterize the flux of platelet-endothelial cell adhesion molecule (PECAM-1) antibody-coated superparamagnetic iron oxide nanoparticles (IONPs) across the blood-brain barrier (BBB) and its biodistribution in vitro and in vivo.MethodsAnti-PECAM-1 IONPs and IgG IONPs were prepared and characterized in house. The binding affinity of these nanoparticles was investigated using human cortical microvascular endothelial cells (hCMEC/D3). Flux assays were performed using a hCMEC/D3 BBB model. To test their immunospecificity index and biodistribution, nanoparticles were given to Sprague Dawley rats by intra-carotid infusion. The capillary depletion method was used to elucidate their distribution between the BBB and brain parenchyma.ResultsAnti-PECAM-1 IONPs were ∼130 nm. The extent of nanoparticle antibody surface coverage was 63.6±8.4%. Only 6.39±1.22% of labeled antibody dissociated from IONPs in heparin-treated whole blood over 4 h. The binding affinity of PECAM-1 antibody (KD) was 32 nM with a maximal binding (Bmax) of 17×105 antibody molecules/cell. Anti-PECAM-1 IONP flux across a hCMEC/D3 monolayer was significantly higher than IgG IONP's with 31% of anti-PECAM-1 IONPs in the receiving chamber after 6 h. Anti-PECAM-1 IONPs showed higher concentrations in lung and brain, but not liver or spleen, than IgG IONPs after infusion. The capillary depletion method showed that 17±12% of the anti-PECAM-1 IONPs crossed the BBB into the brain ten minutes after infusion.ConclusionsPECAM-1 antibody coating significantly increased IONP flux across the hCMEC/D3 monolayer. In vivo results showed that the PECAM-1 antibody enhanced BBB association and brain parenchymal accumulation of IONPs compared to IgG. This research demonstrates the benefit of anti-PECAM-1 IONPs for association and flux across the BBB into the brain in relation to its biodistribution in peripheral organs. The results provide insight into potential application and toxicity concerns of anti-PECAM-1 IONPs in the central nervous system.

Highlights

Multifunctional superparamagnetic iron oxide nanoparticles (IONPs) have various applications, such as diagnosis and therapy of the central nervous system (CNS) [1,2]
The results of this study demonstrate the potential of anti-PECAM-1 IONPs to target and transcytose across the blood-brain barrier (BBB) and enter into the brain parenchyma, providing valuable insight into the feasibility of antiPECAM-1 IONP as a brain targeting magnetic resonance imaging (MRI) contrast agent and/or drug delivery system for the CNS
This work demostrated that anti-PECAM-1-modified IONPs enhance flux across the BBB in vitro and in vivo, which holds promise to deliver IONPs or other therapeutic agents to the CNS without compromising BBB permeability

Summary

Introduction

Multifunctional superparamagnetic iron oxide nanoparticles (IONPs) have various applications, such as diagnosis and therapy of the central nervous system (CNS) [1,2]. Multifunctional IONPs provide the possibility to deliver therapeutic agents to the brain and concurrently monitor their tissue distribution using MRI [5,6]. One of the challenges for CNS applications of IONPs is the ability to cross the highly restricted BBB. There have been no reports distinguishing between IONPs in the brain vessels and BBB cells [7]; or they only showed the therapeutic efficacy of co-delivered compounds in animal models of brain tumors [8]. To advance the potential applications of multifunctional IONPs in the CNS, there is an urgent need to understand how they associate with, and transcytose across, the BBB in vitro and in vivo

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