Figure 1.

The possible strategies for selective delivering bioactive compounds to the bone: (A) a drug or diagnostic agent D is encapsulated/loaded into a conventional nanocarrier (e.g., polymeric or lipid nanoparticles, liposomes, micelles, etc.) and passive targeting is expected (EPR effect); (B) a drug is covalently linked to an osteotropic homing-moiety (e.g., a bisphosphonate, BP) or, a polymeric conjugate bearing the drug and the targetor is produced; (C) smart nanoparticles are produced with a bone-seeking polymer (e.g., the polymer-BP conjugate described in our studies) and then loaded with a bioactive agent; consequently, both passive and active targeting opportunities are achievable.