title: Modification of luminescent iridium(III) polypyridine complexes with discrete poly(ethylene glycol) (PEG) pendants: synthesis, emissive behavior, intracellular uptake, and PEGylation properties.
abstract: We report the synthesis, characterization, and photophysical properties of a new class of luminescent cyclometalated iridium(III) polypyridine poly(ethylene glycol) (PEG) complexes [Ir(N--C)(2)(N--N)](PF(6)) (HN--C=Hppy (2-phenylpyridine), N--N=bpy-CONH-PEG1 (bpy=2,2'-bipyridine; 1a), bpy-CONH-PEG3 (1b); HN--C=Hpq (2-phenylquinoline), N--N=bpy-CONH-PEG1 (2a), bpy-CONH-PEG3 (2b); HN--C=Hpba (4-(2-pyridyl)benzaldehyde), N--N=bpy-CONH-PEG1 (3)) and their PEG-free counterparts (N--N=bpy-CONH-Et, HN--C=Hppy (1c); HN--C=Hpq (2c)). The cytotoxicity and cellular uptake of these complexes have been investigated by the MTT assay, ICPMS, laser-scanning confocal microscopy, and flow cytometry. The results showed that the complexes supported by the water-soluble PEG can act as biological probes and labels with considerably reduced cytotoxicity. Because the aldehyde groups of complex 3 are reactive toward primary amines, the complex has been utilized as the first luminescent PEGylation reagent. Bovine serum albumin (BSA) and poly(ethyleneimine) (PEI) have been PEGylated with this complex, and the resulting conjugates have been isolated, purified, and their photophysical properties studied. The DNA-binding and gene-delivery properties of the luminescent PEI conjugate 3-PEI have also been investigated.
authors.affiliation: Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, P.R. China.
authors.forename: Steve Po-Yam
authors.initials: SP
authors.lastname: Li
authors.forename: Hua-Wei
authors.initials: HW
authors.lastname: Liu
authors.forename: Kenneth Yin
authors.initials: KY
authors.lastname: Zhang
authors.forename: Kenneth Kam-Wing
authors.initials: KK
authors.lastname: Lo
mesh_terms: D000818:Animals; D002417:Cattle; D004563:Electrochemistry; D007495:Iridium / Q000737:chemistry* / Q000633:toxicity; D049449:Luminescence; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry / Q000633:toxicity; D011092:Polyethylene Glycols / Q000737:chemistry* / Q000633:toxicity; D011108:Polymers / Q000737:chemistry*; D011485:Protein Binding; D012710:Serum Albumin, Bovine / Q000737:chemistry* / Q000378:metabolism
chemical_list: D009942:Organometallic Compounds; D011108:Polymers; D012710:Serum Albumin, Bovine; D011092:Polyethylene Glycols; D007495:Iridium