The Binding Avidity of a Nanoparticle-Based Multivalent Targeted Drug Delivery Platform

Abstract

Dendrimer-based anticancer nanotherapeutics containing approximately 5 folate molecules have shown in vitro and in vivo efficacy in cancer cell targeting. Multivalent interactions have been inferred from observed targeting efficacy, but have not been experimentally proven. This study provides quantitative and systematic evidence for multivalent interactions between these nanodevices and folate-binding protein (FBP). A series of the nanodevices were synthesized by conjugation with different amounts of folate. Dissociation constants (K(D)) between the nanodevices and FBP measured by SPR are dramatically enhanced through multivalency ( approximately 2,500- to 170,000-fold). Qualitative evidence is also provided for a multivalent targeting effect to KB cells using flow cytometry. These data support the hypothesis that multivalent enhancement of K(D), not an enhanced rate of endocytosis, is the key factor resulting in the improved biological targeting by these drug delivery platforms.

Folate‐mediated cell uptake of shell‐crosslinked spheres and cylinders

“…22 Then, a folic acid derivative, folate-PEG-amine, was conjugated to the SCKs, and the conjugates were evaluated in cells (Scheme 1). The syntheses of the amphiphilic diblock copolymer, PAA 128 -b-PS 40 , and triblock copolymer, PAA 94 -b-PMA 103 -b-PS 28 , were achieved using atom transfer radical polymerization, following previously reported methods. 21 The block copolymers were then dissolved in a good solvent for both/all blocks (THF or DMF), followed by slow addition of water to induce micellization.…”

“…at 363 nm=6197 M À1 cm À1 Þ= ½polymer ðmg=mLÞ =ðM W of polymer ðg=molÞÞ For PAA 128 -b-PS 40 , which forms the spherical particle, the folate/polymer number was determined to be 3.2; for PAA 94 -b-PMA 103 -b-PS 28 , which forms the cylindrical particle, the folate/polymer number was determined to be 3.0. As expected, no measurable changes were observed in particle morphology after conjugation with folate, as evidenced by TEM (images not shown).…”

“…binding affinities between folate/FR and PTD/cell surface may contribute to the contrasting results for the folate-and PTD-decorated nanostructures. It is hypothesized that a larger structure may span across several FR binding sites and lead to an increase in polyvalent effect 28 and increased FR-mediated endocytosis. By contrast, the PTD-SCKs interact with the cell surface in a receptor-independent fashion 29 and, therefore, may not benefit from polyvalency.…”

“…To a stirring solution of 8.4 mg triblock copolymer, poly(acrylic acid) 94 -b-poly(methyl acrylate) 103 -b-polystyrene 28 (PAA 94 -b-PMA 103 -b-PS 28 ) in 8.00 mL tetrahydrofuran (THF) was added a solution of THF (2.0 mL) containing O-bis(aminoethyl)ethylene glycol (0.20 equiv., relative to COOH groups). The mixture was allowed to stir overnight at room temperature, and then H 2 O (40 mL) was added at a rate of 7.00 mL/h to induce micellization.…”

Ultrasmall Conjugated Polymer Nanoparticles with High Specificity for Targeted Cancer Cell Imaging

“…In particularly, fluorescent nanoparticles (NPs) covalently linked with biorecognition ligands have shown great merits in cancer diagnosis and therapy 5, 6, 7, 8. As compared to molecular dye‐ligand conjugates, the multiple targeting ligands presented on NP surfaces allow multivalent recognition and binding to receptors on cell membrane, resulting in higher binding affinity and much improved selectivity toward targeted cells 9, 10, 11. With the rapid advances of nanotechnology, versatile NP systems including semiconducting quantum dots (QDs), gold NPs, and dye encapsulated NPs, etc., have been developed 12, 13, 14, 15, 16.…”