Dual-Sensitive On-Off Switch in Liposome Bilayer for Controllable Drug Release.

To improve the controllability of drug release from liposome, a series of pH- and photosensitive block copolymers C7H15-AZO- b-PDPAn- b-mPEG were designed and served as an on-off switch in the liposome bilayer. The functional properties of liposomes were studied by dynamic light scattering, fluorophotometry, UV-vis spectroscopy, and fluorescence spectrophotometry. The liposomes with or without copolymer were relatively uniform in size. Their membrane stability was improved obviously after inserting copolymer under pH 7.4, but it decreased in an acidic environment and caused a large amount of drug release. Meanwhile, UV irradiation could also result in more drug release because of the photoisomerization of the azobenzene (AZO) group. Furthermore, intermittent drug-release experiments showed that the PDPA blocks could reversibly get in and out of the liposome bilayer and ultimately realized the complete drug release. All results suggested that the designed copolymers could be inserted into liposome bilayer through self-assembly and could act as a switch for controllable drug release.