“…However, such reaction may be desirable in applications such as vaccination therapies, and when enhanced uptake of exogenous compounds, such as anti-human immunodeficiency virus (HIV) drugs , is sought. Nanoparticle polymeric carriers, when their size is less than 100 nm, have a high potential for being accumulated in tumour sites, according to the enhanced permeation and retention (EPR) effect (Nishikawa et al, 1996;Yasugi et al, 1999). Hydrophilic modification, particularly by introducing poly(ethylene)glycol (PEG) by physical coating or covalent linking -a process known as pegylation -to the surface, prolongs the half-life of the carriers (Kumar, 2000;Seal et al, 2001;Diwan and Park, 2003) during circulation in blood by reducing opsonization and thus minimizing carrier clearance in organs such as liver, spleen, lung and bone marrow (Gref et al, 1994;Peracchia et al, 1997).…”