Role of Unmodified Low Generation – PAMAM Dendrimers in Efficient Non-Toxic Gene Transfection

The present study is focused on a simple execution in the applicability of non-toxic lower generation poly amidoamine (PAMAM) dendrimers as effective nano-vectors in targeted gene delivery to the skin. So far the first three lower generation (G1, G2 and G3) PAMAM dendrimers have been overlooked as nucleic acid therapeutics. In this study, we have first carried out a systematic biophysical analysis to analyze their ability for plasmid DNA (pDNA) condensation and subsequent release by ethidium bromide assay to optimize dendrimer to DNA charge ratio for effective pDNA condensation and release. Interestingly, stopped flow fluorescence spectroscopic analysis on pDNA-dendrimer binding kinetics revealed the efficiency of generations G2 and G3 in pDNA condensation in comparison with G1 through four steps. Importantly, it validates aggregation and association of the dendrimer in the vicinity of pDNA. Based on these understanding, successful in vitro cellular uptake of dendriplexes followed by their transfection into CHO−K1 cells was demonstrated at the charge ratio Z+/- 5 and 10. The interesting observations of gene transfection with CHO−K1 cells were extended to HaCaT cell line and efficient pDNA transfections were evidenced with negligible cytotoxicity. In addition to this, the stability of the dendriplexes at the charge ratio Z+/- 5 for G3 and Z+/- 10 for G2 was found even upto 50 % serum concentration suggesting possible future applicability in in vivo. Overall, the current approach promises the use of lower generation dendrimers for pDNA delivery to the skin using only electrostatic nanocomplex formation without any covalent linkage.