title: Avidity modulation of folate-targeted multivalent dendrimers for evaluating biophysical models of cancer targeting nanoparticles.
abstract: We investigated two types of generation 5 polyamidoamine (PAMAM) dendrimers, each conjugated stochastically with a mean number of 5 or 10 methotrexate (MTX) ligands per dendrimer (G5-MTX5, G5-MTX10), for their binding to surface-immobilized folate binding protein (FBP) as a function of receptor density. The binding study was performed under flow by surface plasmon resonance spectroscopy. Two multivalent models were examined to simulate binding of the dendrimer to the receptor surface, showing that at relatively high receptor density, both dendrimer conjugates exhibit high avidity. However, upon reducing the receptor density by a factor of 3 and 13 relative to the high density level, the avidity of the lower-valent G5-MTX5 decreases by up to several orders of magnitude (KD = nM to μM), whereas the avidity of G5-MTX10 remains largely unaffected regardless of the density variation. Notably, on the 13-fold reduced FBP surface, G5-MTX5 displays binding kinetics similar to that of monovalent methotrexate, which is patently different from the still tight binding of the higher-valent G5-MTX10. Thus, the binding analysis demonstrates that avidity displayed by multivalent MTX conjugates varies in response to the receptor density and can be modulated for achieving tighter, more specific binding to the higher receptor density by modulation of ligand valency. We believe this study provides experimental evidence supportive of the mechanistic hypothesis of multivalent NP uptake to a cancer cell over a healthy cell where the diseased cell expresses the folate receptor at higher density.
authors.affiliation: Michigan Nanotechnology Institute for Medicine and Biological Sciences, ‡Macromolecular Science and Engineering, §Program in Biomedical Sciences, ∥Department of Internal Medicine, ⊥Department of Chemistry, and #Department of Physics, University of Michigan , Ann Arbor, Michigan 48109, United States.
authors.forename: Justin E
authors.initials: JE
authors.lastname: Silpe
authors.forename: Madhuresh
authors.initials: M
authors.lastname: Sumit
authors.forename: Thommey P
authors.initials: TP
authors.lastname: Thomas
authors.forename: Baohua
authors.initials: B
authors.lastname: Huang
authors.forename: Alina
authors.initials: A
authors.lastname: Kotlyar
authors.forename: Mallory A
authors.initials: MA
authors.lastname: van Dongen
authors.forename: Mark M
authors.initials: MM
authors.lastname: Banaszak Holl
authors.forename: Bradford G
authors.initials: BG
authors.lastname: Orr
authors.forename: Seok Ki
authors.initials: SK
authors.lastname: Choi
mesh_terms: D050091:Dendrimers / Q000737:chemistry*; D004337:Drug Carriers / Q000737:chemistry* / Q000378:metabolism; D016503:Drug Delivery Systems; D058973:Folate Receptors, GPI-Anchored / Q000378:metabolism; D005492:Folic Acid / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D053758:Nanoparticles / Q000737:chemistry*; D009369:Neoplasms / Q000188:drug therapy / Q000378:metabolism*; D011073:Polyamines / Q000737:chemistry*
chemical_list: D050091:Dendrimers; D004337:Drug Carriers; D058973:Folate Receptors, GPI-Anchored; C531249:Poly(amidoamine); D011073:Polyamines; D005492:Folic Acid