Small heat shock protein as a multifunctional scaffold: Integrated tumor targeting and caspase imaging within a single cage

Protein cages have the potential to serve as biomaterials for the targeted therapeutic and imaging systems. As an effort to exploit small heat shock protein (Hsp) cages as multifunctional biomaterials, we demonstrate that chemically and genetically modified Hsp cages permeate the cells via cancer cell binding and subsequent endocytic internalization and can image caspase activity in the live cells. Moreover, we report here that these functional Hsp cages can be specifically accumulated to tumor tissues of tumor-bearing mice when administered intravenously through the lateral tail vein. These tumor-targeting properties could be explained by the prolonged in vivo circulation and enhanced permeability and retention (EPR) effect as well as the ligand-mediated binding to cancer cells. Furthermore, when combined with the caspase sensing ability, our Hsp cage allows us to monitor the therapeutic evaluation after anticancer drug treatment by imaging the caspase activity within tumors. Therefore, we demonstrate that the Hsp cages have multifunctional scaffolds amenable to genetic and chemical modifications without loss of the cagelike architecture and can be exploited as biomedical materials including drug or imaging agent carriers.