Side-on binding of p-sulphonatocalix[4]arene to the dinuclear platinum complex trans-[{PtCl(NH3)2}2μ-dpzm]2+ and its implications for anticancer drug delivery

Wheate, N.J. and Abbott, Grainne M. and Tate, Rothwelle J. and Clements, Caorl J. and Edrada-Ebel, RuAngelie and Johnston, B.F. (2009) Side-on binding of p-sulphonatocalix[4]arene to the dinuclear platinum complex trans-[{PtCl(NH3)2}2μ-dpzm]2+ and its implications for anticancer drug delivery. Journal of Inorganic Biochemistry, 103 (3). pp. 448-454. ISSN 0162-0134 (http://dx.doi.org/10.1016/j.jinorgbio.2008.12.011)

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Abstract

The utility of p-sulphonatocalix[4]arene (s-CX[4]) as a drug delivery vehicle for multinuclear platinum anticancer agents, using trans-[{PtCl(NH3)2}2μ-dpzm]2+ (di-Pt; where dpzm = 4,4′-dipyrazolylmethane) as a model complex, has been examined using 1H nuclear magnetic resonance, electrospray ionisation mass spectrometry, molecular modelling and in vitro growth inhibition assays. s-CX[4] binds di-Pt in a side-on fashion in a ratio of 1:1, with the dpzm ligand of the metal complex located within the s-CX[4] cavity with binding further stabilised by ion-ion interactions and hydrogen bonding between the metal complex am(m)ine groups and the s-CX[4] sulphate groups. Partial encapsulation of di-Pt within the cavity does not prevent binding of 5′-guanosine monophosphate to the metal complex. When bound to two individual guanosine molecules, di-Pt also remains partially bound by s-CX[4]. The cytotoxicity of free di-Pt and s-CX[4] and their host guest complex was examined using in vitro growth inhibition assays in the A2780 and A2780cis human ovarian cancer cell lines. Free di-Pt has an IC50 of 100 and 60 μM, respectively, in the cell lines, which is significantly less active than cisplatin (1.9 and 8.1 μM, respectively). s-CX[4] displays no cytotoxicity at concentrations up to 1.5 mM and does not affect the cytotoxicity of di-Pt, probably because its low binding constant to the metal complex (6.8 × 104 M−1) means the host-guest complex is mostly disassociated at biologically relevant concentrations.

ORCID iDs

Wheate, N.J., Abbott, Grainne M., Tate, Rothwelle J., Clements, Caorl J., Edrada-Ebel, RuAngelie and Johnston, B.F. ORCID logoORCID: https://orcid.org/0000-0001-9785-6822;
CORE (COnnecting REpositories)