Endothelial Targeting of High-Affinity Multivalent Polymer Nanocarriers Directed to Intercellular Adhesion Molecule 1

Abstract

Targeting of diagnostic and therapeutic agents to endothelial cells (ECs) provides an avenue to improve treatment of many maladies. For example, intercellular adhesion molecule 1 (ICAM-1), a constitutive endothelial cell adhesion molecule upregulated in many diseases, is a good determinant for endothelial targeting of therapeutic enzymes and polymer nanocarriers (PNCs) conjugated with anti-ICAM (anti-ICAM/PNCs). However, intrinsic and extrinsic factors that control targeting of anti-ICAM/PNCs to ECs (e.g., anti-ICAM affinity and PNC valency and flow) have not been defined. In this study we tested in vitro and in vivo parameters of targeting to ECs of anti-ICAM/ PNCs consisting of either prototype polystyrene or biodegradable poly(lactic-coglycolic) acid polymers (ϳ200 nm diameter spheres carrying ϳ200 anti-ICAM molecules). Anti-ICAM/ PNCs, but not control IgG/PNCs 1) rapidly (t 1/2 ϳ5 min) and specifically bound to tumor necrosis factor-activated ECs in a dose-dependent manner (B max ϳ350 PNC/cell) at both static and physiological shear stress conditions and 2) bound to ECs and accumulated in the pulmonary vasculature after i.v. injection in mice. Anti-ICAM/PNCs displayed markedly higher EC affinity versus naked anti-ICAM (K d ϳ80 pM versus ϳ8 nM) in cell culture and, probably because of this factor, higher value (185.3 Ϯ 24.2 versus 50.5 Ϯ 1.5% injected dose/g) and selectivity (lung/blood ratio 81.0 Ϯ 10.9 versus 2.1 Ϯ 0.02, in part due to faster blood clearance) of pulmonary targeting. These results 1) show that reformatting monomolecular anti-ICAM into high-affinity multivalent PNCs boosts their vascular immunotargeting, which withstands physiological hydrodynamics and 2) support potential anti-ICAM/PNCs utility for medical applications.

Factors modulating the delivery and effect of enzymatic cargo conjugated with antibodies targeted to the pulmonary endothelium

“…We tested distribution of the radiolabeled TM antibodies and GOX conjugates one hour after IV injection. Previous studies of immunotargeting of radiolabeled conjugates directed to highly accessible endothelial determinants such as TM, angiotensin-converting enzyme (ACE), PECAM-1, intercellular adhesion molecule 1 (ICAM-1) and GP90 showed that their maximum uptake in the lungs occurs within 15-30 min, followed by a short 15-30 min stable period and subsequent reduction of the pulmonary level observed at times more than one hour after IV injection [22,25,27,[46][47][48][49][50][51][52]. Therefore, the kinetics of lung edema development showing a maximum 4 hour after injection of a lower dose of the conjugate selected to avoid overt early lethality (Fig.4C) is not due to delayed accumulation of GOX in the lungs.…”

“…Solid poly(lactic-co-glycolic acid) PLGA nanoparticles were prepared by a modified single emulsion technique, as described before [27]. Similar to solvent extraction of microsphere particle preparations reviewed by Freitas et al [28] and other nanoparticle formulations [29] this nanoprecipitation method involves dissolving PLGA in a water miscible solvent, such as acetone, and addition to a stabilizing surfactant solution.…”

Using shape effects to target antibody-coated nanoparticles to lung and brain endothelium

“…To determine whether shape-enhanced endothelial accumulation is also observed under physiological conditions, nanospheres and nanorods coated with ICAM-mAb (YN1/1.7.4) or nonspecific mouse IgG were injected intravascularly into healthy mice. Under healthy conditions, ICAM-1 is expressed at basal levels in the endothelium of the lungs (31,32) and has been used extensively for nanoparticle targeting to the lungs (33). ICAM-mAb-coated spheres and rods exhibited higher accumulation in the lungs compared with their IgG-coated counterparts.…”

Nanomedicine and Drug Delivery Strategies for Treatment of Genetic Diseases

“…Whether it is due to targeting via positively-charged moieties or by specific affinity means, targeted delivery of drug carriers offers advantages over direct targeting of therapeutics. Apart from the described advantages posed by increased solubility, circulation time, and release control, carriers bearing multiple copies of an affinity moiety display greater affinity due to this multivalency, compared to drugs that are directly coupled to one copy of the same affinity molecule (Muro, et al, 2006a). As described below, multivalency of targeted carriers also provides tight binding to cell surface receptors, which can favor uptake within the cell, a necessary requirement for many diagnostic and therapeutic applications.…”