Fig. 1.

Design of bone-targeted protein nanomedicine for the treatment of malignant bone tumors. The ternary complex GPSP is consisted of an intracellular protein delivery carrier GP, a toxin protein saporin and a bone-targeted polyanion PASP. PASP on the surface enhances the accumulation of protein therapeutics in the bone tumor site, and GP facilitates the intracellular delivery of saporin protein into tumor cells. The polymer PASP on GPSP shields the positive charges on GPS nanoparticles during blood circulation, but will be detached on GPS after localization in tumor tissues triggered by tumor extracellular acidity.