pH-Dependent Dissociation of Carbohydrate Ligand Polycations from DNA Ternary Complexes

Abstract

Here, we have demonstrated that carbohydrate ligand polycations are pH-dependently dissociated from DNA polyion complexes. In response to pH, DNA ternary complexes have dissociated the ligand polycations, resulting in DNA binary complexes. Namely, the ternary complexes of DNA, a poly(L-histidine) modified with aminoethyl groups, PLH-NH 2 , and a poly(L-lysine) conjugated with lactose molecules, PLL-Lac, at pH 7.5 have dissociated the PLL-Lac polycations by the protonation of imidazole groups of PLH-NH 2 at pH 6.0. The pH-dependent dissociation of the ligand polycations from DNA polyion complexes at endosomal pH is expected to offer unique design for DNA delivery systems.In gene delivery systems, the formation of DNA-carrier polyion complexes is a key factor for new design of efficient delivery.1 The carrier design typically focuses on the ability of a ligand to bind tightly to its target. The ligand-receptor complexes on the cell plasma membrane are internalized into acidic endosomal vesicles where they are subjected to a significant pH change from pH 7 to 5.2 Subsequently, the targeting ligands are routed to the degradation in the acidic compartment following endosomal vesicles or are recycled to the cell surface.3 Such fate of ligands leads us to create the DNA polyion complexes dissociating ligand molecules in response to pH. In general, targeting ligands are unnecessary to make DNA complexes escape from endosomal vesicles. The endosomal escape is one of the critical factors for efficient gene delivery. If the targeting ligands are conjugated with pH-sensitive polycations, i.e., formation of binary complexes, the pH-dependent peculiar property of the polycations is considered to diminish. The formation of the ternary complexes between ligand polycations, pH-sensitive polycations, and DNA is expected to preserve the property of the pH-sensitive polycations. Here, we communicate that ligand polycations are pH-dependently dissociated from DNA polyion complexes. The concept that DNA ternary complexes dissociate ligand polycations in response to endosomal pH, resulting in DNA binary complexes, has no precedent, to the best of our knowledge. The experimental schema of the pH-dependent dissociation of carbohydrate ligand polycations from DNA polyion complexes is depicted in Figure 1. We have chosen a poly(L-lysine) conjugated with lactose (4-O--D-galactopyranosyl-D-glucose), PLL-Lac, as carbohydrate ligands for an asialoglycoprotein re-

Carboxymethyl Poly(l-histidine) as a New pH-Sensitive Polypeptide To Enhance Polyplex Gene Delivery

“…The neutral or negatively charged nonviral gene carriers have poor ability to interact with the cell membrane. In this study, even without any targeting ligands, 20,21 efficient gene delivery was achieved. The total gene expression depended on the incubation time (Figure S-3, Supporting Information).…”

Zinc-Chelated Poly(1-vinylimidazole) and a Carbohydrate Ligand Polycation Form DNA Ternary Complexes for Gene Delivery

“…We have already reported the concept that DNA ternary complexes dissociate ligand polycations in response to endosomal pH. , In this study, as shown in Figure , we examined the pH-dependent dissociation of PLL-Lac from the DNA ternary complexes with the PLL-Lac and the PVIm-Zn by agarose gel electrophoresis. It should be noted that free DNA was observed in spite of the mixing at a positive/negative ratio of 2 in case of PVIm-Zn/DNA binary complexes at pH 7.4.…”

“…We have already reported pH-sensitive binary or ternary complexes containing imidazole groups for efficient gene delivery. , Especially, gene expression depends on our new concept that DNA ternary complexes dissociate carbohydrate ligand polycations in response to endosomal pH. , However, the charge ratio of polycation to DNA is relatively higher, that is, 5. Furthermore, we have proven that the pH-dependent chelation of Zn 2+ ions with the imidazole groups of poly(1-vinylimidazole) (PVIm) and that the zinc-chelated PVIm (PVIm-Zn) formed the DNA polyion complex via chelated Zn 2+ ions.…”

Poly(1-vinylimidazole) polyplexes as novel therapeutic gene carriers for lung cancer therapy

“…The imidazole ring is involved in many physiological processes and therefore imidazole-containing systems have been investigated for a myriad of biological applications [5]. Poly(vinylimidazole) is a water-soluble polymer, which has been synthesized as poly(1-vinylimidazole) and poly(4-vinylimidazole) [6] by using different methods. The imidazole groups can be protonated at acidic pH values conferring cationic character to the polymer.…”