High intensity focused ultrasound responsive release behavior of metallo-supramolecular block PPG-PEG copolymer micelles.

An amphiphilic metallo-supramolecular poly(propylene glycol)-block-poly(ethylene glycol) block copolymer containing a bis(2,2':6',2″-terpyridine) ruthenium (II) complex as a supramolecular connection between the two constituting blocks was used to prepare stable aqueous micelles which displayed a high intensity focused ultrasound (HIFU) triggered release behavior. By adjusting the HIFU time and intensity, the novel modality of HIFU triggered release allows for fine-tuning of the release kinetics of the encapsulants from the micelles in a remote and controlled way. Nuclear magnetic resonance spectroscopy, ultraviolet spectroscopy, and matrix-assisted laser desorption/ionization-time of flight mass spectrometry confirmed that the degradation of the micelles was due to the cleavage of the ether bond connected to the pyridine ring. This well controlled HIFU-copolymer micelle drug delivery system has considerable potential in targeted therapy.