pH‐Responsive Multi‐PEGylated Dual Cationic Nanoparticles Enable Charge Modulations for Safe Gene Delivery

Abstract

In gene therapy, the cytotoxicity of many polycations is undesirable and has been attributed to nonspecific membrane destabilizing effects and intracellular polyplex-mediated toxicity. To help prolong the pharmacokinetic profile of nonviral vehicles for gene delivery, the cationic surface charge of current systems is typically shielded through the conjugation of polyethylene glycol (PEG) chains to the particle surface. However, the design of an intelligent polycation with environment-sensing charge modulations is essential to minimize cytotoxicity and enhance gene expression. We have designed a novel di-cationic block copolymer, poly(aspartate-hydrazide)-block-poly(L-lysine), capable of pH-mediated endosomal membrane disruption based on charge interactions, which has negligible toxicity elsewhere to the cell. The poly(L-lysine) segment, with a high pK(a) value of approximately 9.4, preferentially forms a poly-ion complex with the negative phosphate groups of pDNA, whereas the pH-responsive poly(aspartate-hydrazide) segment, with the comparatively lower pK(a) approximately 5.0, is characterized by a substantial fraction of unprotonated amino groups at physiological pH. As a consequence, complexation between such a polymer and pDNA leads to the formation of a two-layered nanoparticle. In particular, the nanoparticle possesses an unprotonated pH-responsive segment to serve as both a scaffold for acid-labile linkages of various moieties such as aldehyde-PEG and to transition from neutral to charged for disrupting endosomal membranes, and safely enhancing gene expression. Our system supports an endosomal escape mechanism based on charge interactions rather than the proton-sponge effect, and may be an important step towards engineering new classes of intelligent nonviral vectors.

Histamine-functionalized copolymer micelles as a drug delivery system in 2D and 3D models of breast cancer

“…37, 38 Therefore, efforts have been directed toward the design of non-toxic nanocarriers with pH-responsive charge properties. Kataoka et al have developed various polymer-based nanocarriers for pDNA 3, 39, 40 and siRNA 41, 42 delivery. For example, the Kataoka group have recently reported a pH-reversible polymer platform based on maleic acid amide (MAA) for endosomal escape of siRNA by switching from negatively to positively charged MAA residues when the compound is exposed to an acidic environment.…”

Chemically Programmed Polymers for Targeted DNA and siRNA Transfection

“…In this way the cationic charges of the polyplex are exposed at the polyplex surface for endosomal membrane destabilization, and hence release from the endosome, further enhancing transfection activity. Acid labile polymer-PEG linkages such as acetals [49,50], acetone-bis-(N-maleimidoethyl)ketal linkers [51], ortho esters [52], and hydrazones [53,54] were introduced and transfection tests have confirmed the increased nucleic acid activity compared to stable PEG conjugations.…”

Scope of nanotechnology in ovarian cancer therapeutics

“…The leaky vasculature promotes the uptake of nanoformulations by the tumors, which become entrapped inside, and due to impaired and poor lymphatic drainage, promotes Enhanced Permeation and Retention (EPR) index. In addition, the size and charge of nanoparticles dictates the passive targeting to the tumors [25-28]. In comparison, the active targeting mode utilizes the conjugation of nanoparticles to immunogens (antibodies or targeting moieties).…”