A facile synthesis and physical properties of nano-sized dendritic alpha,epsilon-poly(L-lysine)s for the delivery of nucleic acids.

A series of nano-sized dendritic alpha,epsilon-poly(L-lysine)s (DPL) were synthesized by the solid-phase peptide synthesis method, using a core epsilon-peptide structure consisting of eight lysine residues. Surface amines of dendritic alpha,epsilon-poly(L-lysine) were characterized by comparing the retention times of a reverse phase HPLC with the electrophoretic mobilities of capillary zone electrophoresis (CZE) and non-denatured polyacrylamide gel electrophoresis (PAGE). The elution times of alpha,epsilon-poly(Llysine) in HPLC were well correlated with the electrophoretic mobilities of CZE and PAGE. The separation was dependent on size, shape of molecule and the number of surface amine. The alpha,epsilon-poly(L-lysine) formed a complex with nucleic acids at various charge ratios and the degree of complex formation was size- and structure-dependent. Atomic force microscopy of the complex visualized the size and morphology of alpha,epsilon-poly(L-lysine)/DNA complex as a nano-sized spherical shape. The small size in complex formation provides a promise for in vivo therapeutic application of dendritic alpha,epsilon-poly(L-lysine)s or their derivatives in the delivery of gene or oligonucleotide.