Enhanced kinetic stability of [Pd2L4](4+) cages through ligand substitution
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Author(s)
Preston, Dan
McNeill, Samantha M
Lewis, James EM
Giles, Gregory I
Crowley, James D
Type
Journal Article
Abstract
There is considerable interest in exploiting metallosupramolecular cages as drug delivery vectors. Recently, we developed a [Pd2L4]4+ cage capable of binding two molecules of cisplatin. Unfortunately, this first generation cage was rapidly decomposed by common biologically relevant nucleophiles. In an effort to improve the kinetic stability of these cage architectures here we report the synthesis of two amino substituted tripyridyl 2,6-bis(pyridin-3-ylethynyl)pyridine (tripy) ligands (with amino groups either in the 2-(2A-tripy) or 3-(3A-tripy) positions of the terminal pyridines) and their respective [Pd2(Ltripy)4]4+ cages. These systems have been characterised by 1H, 13C and DOSY NMR spectroscopies, high resolution electrospray mass spectrometry, elemental analysis and, in one case, by X-ray crystallography. It was established, using model palladium(II) N-heterocyclic carbene (NHC) probe complexes, that the amino substituted compounds were stronger donor ligands than the parent system (2A-tripy > 3A-tripy > tripy). Competition experiments with a range of nucleophiles showed that these substitutions lead to more kinetically robust cage architectures, with [Pd2(2A-tripy)4]4+ proving the most stable. Biological testing on the three ligands and cages against A549 and MDA-MB-231 cell lines showed that only [Pd2(2A-tripy)4]4+ exhibited any appreciable cytotoxicity, with a modest IC50 of 36.4 ± 1.9 μM against the MDA-MB-231 cell line. Unfortunately, the increase in kinetic stability of the [Pd2(Ltripy)4]4+ cages was accompanied by loss of cisplatin-binding ability.
Date Issued
2016-04-06
Date Acceptance
2016-04-05
Citation
Dalton Transactions, 2016, 45 (19), pp.8050-8060
ISSN
1477-9234
Publisher
Royal Society of Chemistry
Start Page
8050
End Page
8060
Journal / Book Title
Dalton Transactions
Volume
45
Issue
19
Copyright Statement
This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
License URL
Subjects
Science & Technology
Physical Sciences
Chemistry, Inorganic & Nuclear
Chemistry
SOLUBLE ORGANOMETALLIC CAGES
ASSEMBLED COORDINATION CAGES
DRUG-DELIVERY
SPIN-CROSSOVER
METALLOSUPRAMOLECULAR ARCHITECTURES
CANCER-CELLS
PT-II
PD-II
COMPLEXES
RELEASE
Publication Status
Published