Preparation, characterisation and bioactivity evaluation of the inclusion complex formed between picoplatin and γ-cyclodextrin

• Picoplatin/γ-CD has been characterised by apparatuses and experimental approaches.
• The water solubility of picoplatin complex was obviously improved by complexation.
• The complex still maintains good antitumor activities against A549 and MCF-7 cells.
• The binding free energy of picoplatin complex was calculated.

The inclusion complex of picoplatin with γ-cyclodextrin (γ-CD) was prepared and characterised by different analytical methods, including NMR, FTIR, TGA, phase solubility as well as SEM. All of these approaches indicated that picoplatin was able to form an inclusion complex with γ-CD, and that the picoplatin/γ-CD inclusion compounds exhibited different spectroscopic features and properties from free picoplatin. The stoichiometry of the complex was 1:1; the pyridine group of picoplatin was deeply inserted into the cavity of γ-CD and the amine platinum group of picoplatin was near the narrower rim of γ-CD. The calculated apparent stability constant of the complex was 10,318 M−1. Moreover, the water solubility of picoplatin was significantly improved, according to phase-solubility studies. The complex maintained its anticancer activity, as shown by an in vitro cell-survival assay on A549 and MCF-7 cancer cell lines. All of these results showed that inclusion complexation may be a promising strategy to design a novel formulation of picoplatin as an anticancer therapy.

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