Theranostic polymeric micelles, containing dichloro(1,2-diaminocyclohexane)platinum(II) (DACHPt) and gadolinium-diethylenetriaminepentaacetic acid (Gd- DTPA) for the simultaneous treatment and imaging of cancer were prepared through the metal complex formation of DACHPt with Gd-DTPA and poly(ethylene glycol)-b-poly(glutamic acld) [PEG-b-P(Glu)] block copolymer. The DACHPt/Gd-DTPA-loaded micelles were approximately 40 nm in diameter with narrow size distribution. The DACHPt/Gd-DTPA-loaded micelles were stable in phosphate buffer saline (pH 7.4) at 37°C keeping the initial intensity for 24 hour. Both of platinum and gadolinium from the micelles revealed a sustained release rate. In relaxivity studies, the micelles showed 20 times higher relaxivity compared to free Gd-DTPA. In vivo biodistribution, antitumor activity and MRI experiments were performed on CDF1 mice bearing the murine colon carcinoma C-26 inoculated subcutaneously. DACHPt/Gd-DTPA-loaded micelles showed higher accumulation to the solid tumor than free drugs. The micelle showed much higher antitumor efficacy than oxaliplatin and more than 2 times stronger and much longer contrast enhancement of the tumor than Gd-DTPA in MRI imaging suggesting the high potential of DACHPt/Gd-DTPA-loaded micelles as theranostic nanodevices.
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