Intracellular Environment-Responsive Stabilization of Polymer Vesicles Formed from Head-Tail Type Polycations Composed of a Polyamidoamine Dendron and Poly(L-lysine)

Abstract

For the development of effective drug carriers, nanocapsules that respond to micro-environmental changes including a decrease in pH and a reductive environment were prepared by the stabilization of polymer vesicles formed from head-tail type polycations, composed of a polyamidoamine dendron head and a poly(L-lysine) tail (PAMAM dendron-PLL), through the introduction of disulfide bonds between the PLL tails. Disulfide bonds were successfully introduced through the reaction of Lys residues in the PAMAM dendron-PLL polymer vesicles with 2-iminothiolane. The stabilization of PAMAM dendron-PLL polymer vesicles was confirmed by dynamic light scattering measurements. In acid-base titration experiments, nanocapsules cross-linked by disulfide bonds had a buffering effect during the cellular uptake process. The PAMAM dendron-PLL nanocapsules were used to incorporate the fluorescent dyes rhodamine 6G and fluorescein as a drug model. Cationic rhodamine 6G was generally not released from the nanocapsules because of the electrostatic barrier of the PLL membrane. However, the nanocapsules were destabilized at high glutathione concentrations corresponding to intracellular concentrations. Rhodamine 6G was immediately released from the nanocapsules because of destabilization upon the cleavage of disulfide bonds. This release of rhodamine 6G from the nanocapsules was also observed in HeLa cells by laser confocal microscopy.

Doxorubicin Delivery Using pH and Redox Dual-Responsive Hollow Nanocapsules with a Cationic Electrostatic Barrier

“…On the other hand, the increase in GSH concentration in the outer medium had no influence to DOX release from X-linked nanocapsules. There was a critical GSH concentration for the collapse of SS-bonded nanocapsules between 20 and 50 μM [ 20 ]. By increasing the GSH concentration to an intracellular level, which is over the critical GSH concentration, SS-bonded nanocapsules were destabilized through dissociation of the SS bonds between PLL tails, and then, DOX release from the nanocapsules was immediate.…”

“…Self-assembled PAMAM dendron-PLL polymer vesicles were prepared according to a previous report [ 18 , 19 , 20 ]. Briefly, PAMAM dendron-PLL was dissolved in a 50:50 ( v / v ) mixture of distilled water and methanol, and MeOH was then added dropwise with vigorous stirring to produce an 80 vol % methanol solution.…”

“…We have investigated self-assembled polymer vesicles of head-tail type polycations composed of a polyamidoamine dendron head and a poly( l -lysine) tail (PAMAM dendron-PLL) as a nanocarrier in the DDS field [ 14 , 15 , 16 , 17 ]. PAMAM dendron-PLL spontaneously forms polymer vesicles with a narrow size distribution through a coil-to-helix transition of PLL tails in a mixing solvent of water and methanol with high methanol content [ 18 ], and hollow nanocapsules were successfully prepared through the introduction of covalent or SS cross-linkages between primary amines in PLL tails in polymer vesicles [ 19 , 20 ]. The SS-bonded nanocapsules have pH and redox dual responses, in which nanocapsules respond to a decrease in pH from physiological to endosomal pH and an increase in glutathione levels.…”

“…With both features, the nanocapsules can escape from the endosome and release the entrapped molecules through destabilization of the nanocapsules in the cytosol. Importantly, the protonated SS-bonded PLL membrane in the nanocapsule functions as an electrostatic barrier against the cationic molecules entering the nanocapsules, and the entrapped cationic molecules in the nanocapsules cannot be released from the nanocapsules due to the presence of this electrostatic barrier [ 20 ]. Such properties of SS-bonded nanocapsules may be suitable for the delivery of doxorubicin (DOX), because DOX has a primary amine with a p K a of 8.3 [ 21 , 22 ] and is cationic at physiological pH (pH 7.4).…”

Neuroligin-2-derived peptide-covered polyamidoamine-based (PAMAM) dendrimers enhance pancreatic β-cells' proliferation and functions

“…Indeed, A. Harada reported the conjugation of PAMAM via a 2-iminothiolane linker to polylysine; however, the S-S bond was used for coupling by the authors and not the peptide-3-(alkylthio)pyrrolidine-2,5-dione moiety, as we used. 86 To prove that HSA-28 conjugates with the PAMAM dendrimers to a sufficient extent, we applied a nontraditional method for the conjugation chemistry technique: SDS-PAGE. Based on the positions of the molecular weight markers, the average size (50 kDa) and the covering efficiency (around 16%) of the modified PAMAM dendrimers were identified ( Fig.…”