A magnetic chitosan hydrogel for sustained and prolonged delivery of Bacillus Calmette-Guérin in the treatment of bladder cancer

The aim of this study was to develop a magnetic thermosensitive hydrogel as intravesical Bacillus Calmette-Guérin (BCG) delivery system, which was formulated with chitosan (CS), β-glycerophosphate (GP) and Fe3O4 magnetic nanoparticle (Fe3O4-MNP). The gelation time and magnetic response of the gel system were investigated. The morphology of the gel was displayed by scanning electron microscope. Frozen section examination was creatively employed for exhibiting the structure of the gel and determining its intravesical residence time. The antitumor effect and local immune activity of BCG loaded magnetic gel were evaluated. The flowing solution of CS/GP under room temperature could gelate rapidly at body temperature both in vitro and in vivo. The magnetic injectable hydrogels significantly prolonged intravesical BCG residence time under an applied magnetic field. In comparison to traditional BCG therapy for superficial bladder tumor, BCG delivered by the gel system induced a stronger Th1 immune response and revealed higher antitumor efficacy.