title: Nanoparticle multivalency counterbalances the ligand affinity loss upon PEGylation.
abstract: The conjugation of receptor ligands to shielded nanoparticles is a widely used strategy to precisely control nanoparticle-cell interactions. However, it is often overlooked that a ligand's affinity can be severely impaired by its attachment to the polyethylene glycol (PEG) chains that are frequently used to protect colloids from serum protein adsorption. Using the model ligand EXP3174, a small-molecule antagonist for the angiotensin II receptor type 1 (AT1R), we investigated the ligand's affinity before and after its PEGylation and when attached to PEGylated nanoparticles. The PEGylated ligand displayed a 580-fold decreased receptor affinity compared to the native ligand. Due to their multivalency, the nanoparticles regained a low nanomolar receptor affinity, which is in the range of the affinity of the native ligand. Moreover, a four orders of magnitude higher concentration of free ligand was required to displace PEGylated nanoparticles carrying EXP3174 from the receptor. On average, one nanoparticle was decorated with 11.2 ligand molecules, which led to a multivalent enhancement factor of 22.5 compared to the monovalent PEGylated ligand. The targeted nanoparticles specifically bound the AT1R and showed no interaction to receptor negative cells. Our study shows that the attachment of a small-molecule ligand to a PEG chain can severely affect its receptor affinity. Concomitantly, when the ligand is tethered to nanoparticles, the immense avidity greatly increases the ligand-receptor interaction. Based on our results, we highly recommend the affinity testing of receptor ligands before and after PEGylation to identify potent molecules for active nanoparticle targeting.
authors.affiliation: Department of Pharmaceutical Technology, University of Regensburg, Universitaetsstrasse 31, 93053 Regensburg, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Hennig
authors.affiliation: Department of Pharmaceutical Technology, University of Regensburg, Universitaetsstrasse 31, 93053 Regensburg, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Pollinger
authors.affiliation: Department of Pharmaceutical Technology, University of Regensburg, Universitaetsstrasse 31, 93053 Regensburg, Germany.
authors.forename: Anika
authors.initials: A
authors.lastname: Veser
authors.affiliation: Department of Pharmaceutical Technology, University of Regensburg, Universitaetsstrasse 31, 93053 Regensburg, Germany.
authors.forename: Miriam
authors.initials: M
authors.lastname: Breunig
authors.affiliation: Department of Pharmaceutical Technology, University of Regensburg, Universitaetsstrasse 31, 93053 Regensburg, Germany. Electronic address: achim.goepferich@chemie.uni-regensburg.de.
authors.forename: Achim
authors.initials: A
authors.lastname: Goepferich
mesh_terms: D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000008:administration & dosage / Q000494:pharmacology; D045744:Cell Line, Tumor; D003102:Colloids; D016503:Drug Delivery Systems; D006801:Humans; D007093:Imidazoles / Q000008:administration & dosage / Q000494:pharmacology; D008024:Ligands; D019808:Losartan; D053758:Nanoparticles / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry*; D051381:Rats; D044140:Receptor, Angiotensin, Type 1 / Q000378:metabolism; D013777:Tetrazoles / Q000008:administration & dosage / Q000494:pharmacology
chemical_list: D000889:Anti-Arrhythmia Agents; D003102:Colloids; D007093:Imidazoles; D008024:Ligands; D044140:Receptor, Angiotensin, Type 1; D013777:Tetrazoles; D011092:Polyethylene Glycols; C066026:losartan carboxylic acid; D019808:Losartan
keywords: Active targeting; EXP3174 (PubChem CID: 108185); Multivalency; Nanoparticles; PEGylation; Quantum dots; Small molecules