Apart from surface chemistry specific to cell of lymph nodes, how to consider factors like reynold's number, inertial and frictional forces in blood that the cargo would face?
I understand that the main key with nanoparticles (NP) in blood is the immune system. It recognize NP as a strange body, and they finish at liver, kidney and spleen, and only a small amount at tumours. When you add NP in blood, you introduces a big area (surface) and it will be cover by a crown of different serum proteins that increase the size of NP (http://www.ncbi.nlm.nih.gov/pubmed/22191645/).
NPs suffer great changes at their surface in a biological system. You really need to keep in mind those!!!