Targeting Hepatic Cancer Cells with PEGylated Dendrimers Displaying N-Acetylgalactosamine and SP94 Peptide Ligands

Poly(amidoamine) (PAMAM) dendrimers are branched water-soluble polymers defined by consecutive generation numbers (Gn) indicating a parallel increase in size, molecular weight, and number of surface groups available for conjugation of bioactive agents. In this article, we compare the biodistribution of N-acetylgalactosamine (NAcGal)-targeted [C-14](1)-G5-(NH2)(5)-(Ac)(108)-(NAcGal)(14) particles to non-targeted [C-14](1)-G5-(NH2)(127) and PEGylated [C-14](1)-G5-(NH2)(44)-(Ac)(73)-(PEG)(10) particles in a mouse hepatic cancer model. Results show that both NAcGal-targeted and non-targeted particles are rapidly cleared from the systemic circulation with high distribution to the liver. However, NAcGal-targeted particles exhibited 2.5-fold higher accumulation in tumor tissue compared to non-targeted ones. In comparison, PEGylated particles showed a 16-fold increase in plasma residence time and a 5-fold reduction in liver accumulation. These results motivated us to engineer new PEGylated G5 particles with PEG chains anchored to the G5 surface via acid-labile cis-aconityl linkages where the free PEG tips are functionalized with NAcGal or SP94 peptide to investigate their potential as targeting ligands for hepatic cancer cells as a function of sugar conformation ( versus ), ligand concentration (100-4000 nM), and incubation time (2 and 24 hours) compared to fluorescently (Fl)-labeled and non-targeted G5-(Fl)(6)-(NH2)(122) and G5-(Fl)(6)-(Ac)(107)-(cPEG)(15) particles. Results show G5-(Fl)(6)-(Ac)(107)-(cPEG[NAcGal])(14) particles achieve faster uptake and higher intracellular concentrations in HepG2 cancer cells compared to other G5 particles while escaping the non-specific adsorption of serum protein and phagocytosis by Kupffer cells, which make these particles the ideal carrier for selective drug delivery into hepatic cancer cells.