title: Modulation of G protein-coupled adenosine receptors by strategically functionalized agonists and antagonists immobilized on gold nanoparticles.
abstract: Gold nanoparticles (AuNPs) allow the tuning of pharmacokinetic and pharmacodynamic properties by active or passive targeting of drugs for cancer and other diseases. We have functionalized gold nanoparticles by tethering specific ligands, agonists and antagonists, of adenosine receptors (ARs) to the gold surface as models for cell surface interactions with G protein-coupled receptors (GPCRs). The AuNP conjugates with chain-extended AR ligands alone (PEGylated nucleosides and nonnucleosides, anchored to the Au via thioctic acid) were found to be insoluble in water due to hydrophobic entities in the ligand. Therefore, we added a second, biologically inactive pendant moiety to increase the water solubility, consisting of a PEGylated chain terminating in a carboxylic or phosphate group. The purity and stability of the immobilized biologically active ligand were examined by ultrafiltration and HPLC. Pharmacological receptor binding studies on these GPCR ligand-derivatized AuNPs (2-5 nm in diameter), performed using membranes of mammalian cells stably expressing human A1, A2A, and A3ARs, showed that the desired selectivity was retained with K(i) values (nanomolar) of A3AR agonist 21b and A2AAR antagonists 24 and 26a of 14 (A3), 34 (A2A), and 69 (A2A), respectively. The corresponding monomers displayed K i values of 37, 61, and 1,420 nM, respectively. In conclusion, we have synthesized stable, water-soluble AuNP derivatives of tethered A3 and A2AAR ligands that retain the biological properties of their monomeric ligands and are intended for therapeutic and imaging applications. This is the first prototypical application to gold carriers of small molecule (nonpeptide) GPCR ligands, which are under investigation for treatment of cancer and inflammatory diseases.
authors.affiliation: Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0810, USA.
authors.forename: P Suresh
authors.initials: PS
authors.lastname: Jayasekara
authors.forename: Khai
authors.initials: K
authors.lastname: Phan
authors.forename: Dilip K
authors.initials: DK
authors.lastname: Tosh
authors.forename: T Santhosh
authors.initials: TS
authors.lastname: Kumar
authors.forename: Steven M
authors.initials: SM
authors.lastname: Moss
authors.forename: Guofeng
authors.initials: G
authors.lastname: Zhang
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Barchi
authors.forename: Zhan-Guo
authors.initials: ZG
authors.lastname: Gao
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Jacobson
mesh_terms: D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D006046:Gold / Q000493:pharmacokinetics / Q000494:pharmacology; D057809:HEK293 Cells; D006801:Humans; D053768:Metal Nanoparticles; D058906:Purinergic P1 Receptor Agonists / Q000138:chemical synthesis* / Q000493:pharmacokinetics / Q000494:pharmacology; D058915:Purinergic P1 Receptor Antagonists / Q000138:chemical synthesis* / Q000493:pharmacokinetics / Q000494:pharmacology; D043562:Receptors, G-Protein-Coupled
chemical_list: D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D043562:Receptors, G-Protein-Coupled; D006046:Gold