Figure 1.
Barriers to in vivo nanoparticle delivery following intravascular administration. For nanoparticles to successfully reach their targets, they must pass several barriers. This example uses intravascular administration as a case study; other routes of administration are reviewed elsewhere.10−17 Unless immune responses are specifically desired, the nanoparticles must evade recognition by the innate and adaptive immune system during circulation (e.g., the complement system, the mononuclear phagocytic system (MPS), and B cells). Once near the target organ, they must travel past endothelial cells and tight junctions, which line blood vessels. Then the nanoparticles must travel through extracellular matrices within the target tissue, and once they reach the target cells, must access their intended subcellular compartment for therapeutic payload delivery. Reprinted with permission.(8)