Eukaryotic cell toxicity and HSA binding of [Ru(Me4phen)(bb7)]2+ and the effect of encapsulation in cucurbit[10]uril

Biyun Sun, Ian F. Musgrave, Anthony I. Day, Kirsten Heimann, F. Richard Keene*, J. Grant Collins

*Corresponding author for this work

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

The toxicity (IC50) of a series of mononuclear ruthenium complexes containing bis[4(4'-methyl-2,2'-bipyridyl)]-1,n-alkane (bbn) as a tetradentate ligand against three eukaryotic cell lines-BHK (baby hamster kidney), Caco-2 (heterogeneous human epithelial colorectal adenocarcinoma) and Hep-G2 (liver carcinoma)-have been determined. The results demonstrate that cis-α-[Ru(Me4 phen)(bb7)]2+ (designated as α-Me4phen-bb7 , where Me4 phen = 3,4,7,8-tetramethyl-1,10-phenanthroline) showed little toxicity toward the three cell lines, and was considerably less toxic than cis-α-[Ru(phen)(bb12)]2+ (α-phen-bb12) and the dinuclear complex [{Ru(phen)2}2{μ-bb12}]4+. Fluorescence spectroscopy was used to study the binding of the ruthenium complexes with human serum albumin (HSA). The binding of α-Me4phen-bb7 to the macrocyclic host molecule cucurbit[10]uril (Q[10]) was examined by NMR spectroscopy. Large upfield 1H NMR chemical shift changes observed for the methylene protons in the bb7 ligand upon addition of Q[10], coupled with the observation of several intermolecular ROEs in ROESY spectra, indicated that α-Me4phen-bb7 bound Q[10] with the bb7 methylene carbons within the cavity and the metal center positioned outside one of the portals. Simple molecular modeling confirmed the feasibility of the binding model. An α-Me4phen-bb7-Q[10] binding constant of 9.9 ± 0.2 × 106 M-1 was determined by luminescence spectroscopy. Q[10]-encapsulation decreased the toxicity of α-Me4phen-bb7 against the three eukaryotic cell lines and increased the binding affinity of the ruthenium complex for HSA. Confocal microscopy experiments indicated that the level of accumulation of α-Me4phen-7 in BHK cells is not significantly affected by Q[10]-encapsulation. Taken together, the combined results suggest that α-Me4phen-7 could be a good candidate as a new antimicrobial agent, and Q[10]-encapsulation could be a method to improve the pharmacokinetics of the ruthenium complex.

Original languageEnglish
Article number595
Pages (from-to)1-12
Number of pages12
JournalFrontiers in Chemistry
Volume6
Issue numberNOV
DOIs
Publication statusPublished - 1 Nov 2018
Externally publishedYes

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Bibliographical note

Copyright the Author(s) 2018. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

Keywords

  • Cucurbit[10]uril
  • Cytotoxicity
  • HSA binding
  • Ruthenium complexes
  • Supramolecular chemistry

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