Surface charge-dependent intracellular fate of doxorubicin drug delivery systems based on PAMAM dendrimers

Abstract: Dendritic polymers have a huge potential as a molecular cargoes with targeting abilities in diagnosis and treatment of cancer. In our study we synthesized derivates of PAMAM dendrimers using pH-sensitive  linkers... [ view full abstract ]

Abstract: Dendritic polymers have a huge potential as a molecular cargoes with targeting abilities in diagnosis and treatment of cancer. In our study we synthesized derivates of PAMAM dendrimers using pH-sensitive  linkers to promote the absorption or release rate of the drug and to reduce the levels of nonspecific internalization. The amine-terminated (16 primary amino-groups) and acetyl-terminated (14 primary amino-groups out of 16 were blocked) 2nd generation PAMAM dendrimers (G2 and G2_ac respectively) were conjugated with doxorubicin (Dox). G2 and G2_ac derivates labeled by Dox were absorbed by the cells at 37°C with different efficiency. The fluorescence intensity of the cells (SKVO3 and SKVLB cells) incubated with unmodified G2-Dox during 4 h was a bit higher than the fluorescence of the cells exposed to  G2_ac-Dox and free Dox during the same time intervals. After 24 h of incubation differences in fluorescence levels and pattern of distribution between conjugates revealed – after 24h exposition of both cell lines cells to G2_ac-Dox fluorescence was observed in the nuclei. Pattern of distribution and fluorescence intensity of each conjugate was specific and did not depend on sensitivity or resistance cell line used to Dox. At the same time SKVLB cells were much more resistant to free Dox and did not show significant levels of internalization. The results obtained indicate cellular internalization pathways dependence on the nature and charge of surface chemical groups of dendrimers used. Simultaneously, G2_ac-Dox localization in late endosomes and lysosomes allowed Dox to release and migrate into cell nuclei (during longer periods of incubation), where its target – DNA is located. Our study show difference in action pathways on tumor cells of amine terminated conjugate G2-Dox and G2_ac-Dox, what has been confirmed by studies on the endocytosis, intracellular distribution, and cytotoxicity. 

The research was supported by grant of Russian Scientific Foundation # 15-15-10013.