A brief perspective on the diverging theories of lymphatic targeting with colloids.

For targeted delivery of colloids to the lymphatic system, the colloids should efficiently reach and remain in the lymphatics for a considerable period of time. As per the current knowledge, diffusion and phagocytosis are the two mechanisms through which colloids reach the lymphatic system. Several parameters including particle size and charge have been shown to affect the direct uptake of colloids by the lymphatic system. Although many researchers attached ligands on the surface of colloids to promote phagocytosis-mediated lymphatic delivery, another school of thought suggests avoidance of phagocytosis by use of carriers like polyethylene glycol (PEG)ylated colloids to impart stealth attributes and evade phagocytosis. In this perspective, we weigh up the paradoxical theories and approaches available in the literature to draw conclusions on the conditions favorable for achieving efficient lymphatic targeting of colloids.