Analysis of montmorillonite clay as a vehicle in platinum anticancer drug delivery

As a proof-of-concept study, the platinum anticancer complex [(1,10-phenanthroline)(1S,2S-diaminocyclohexane)platinum(II)]chloride, PHENSS, was loaded into montmorillonite (MMT) clay to evaluate its utility as a drug delivery vehicle. Loading is complete within one hour and the total amount of PHENSS that can be loaded into the clay is based on the PHENSS solution concentration in which the MMT is suspended. From a PHENSS solution concentration of 30 mM, a maximum loading of 0.257 mmol per gram of MMT can be achieved. The pH of the solution also has an effect with a solution pH of 6 giving maximum loading of PHENSS. Metal complex release from the MMT was examined using the dialysis bag and dispersion methods. PHENSS is incompletely released from MMT; after 4 h just 47% has been released from the clay using the dialysis method and 30% using the dispersion method. The release is also very fast with a half-life of just 10–16 min. The MMT was shown to have a negative effect on the in vitro cytotoxicity of PHENSS in the human breast cancer cell lines MCF-7 and MDA-MB-231, presumably due to the incomplete release of the metal complex from the clay. Overall the results demonstrate that MMT is not a suitable slow release vehicle for PHENSS, although it may still be of use to other platinum complexes and drugs.