Synthesis and mechanistic investigations of pH-responsive cationic poly(aminoester)s

Abstract

The synthesis and degradation mechanisms of a class of pH-sensitive, rapidly degrading cationic poly(aaminoester)s are described. These reactive, cationic polymers are stable at low pH in water, but undergo a fast and selective degradation at higher pH to liberate neutral diketopiperazines. Related materials incorporating oligo(a-amino ester)s have been shown to be effective gene delivery agents, as the charge-altering degradative behavior facilitates the delivery and release of mRNA and other nucleic acids in vitro and in vivo. Herein, we report detailed studies of the structural and environmental factors that lead to these rapid and selective degradation processes in aqueous buffers. At neutral pH, poly(aaminoester)s derived from N-hydroxyethylglycine degrade selectively by a mechanism involving sequential 1,5-and 1,6-O/N acyl shifts to generate bis(N-hydroxyethyl) diketopiperazine. A family of structurally related cationic poly(aminoester)s was generated to study the structural influences on the degradation mechanism, product distribution, and pH dependence of the rate of degradation. The kinetics and mechanism of the pH-induced degradations were investigated by 1 H NMR, model reactions, and kinetic simulations. These results indicate that polyesters bearing a-ammonium groups and appropriately positioned N-hydroxyethyl substituents are readily cleaved (by intramolecular attack) or hydrolyzed, representing dynamic "dual function" materials that are initially polycationic and transform with changing environment to neutral products. Fig. 1 Proposed mRNA binding and release by Charge-Altering Releasable Transporters (CARTs). Selective degradation of the polycationic poly(a-aminoester) block generates neutral diketopiperazines and hydrolyzed N-hydroxyethyl glycines.Fig. 2 Synthesis of azalactone monomers and polymers.

Fingolimod-Conjugated Charge-Altering Releasable Transporters Efficiently and Specifically Deliver mRNA to Lymphocytes In Vivo and In Vitro

“…CARTs spontaneously form NPs upon simple mixing with oligonucleotides or other polyanionic cargos, and CART/mRNA NPs were shown to be effective in pre-clinical studies of vaccines for cancer , and SARS-CoV2 . The modular and efficient synthesis of the CART amphiphiles (eq ) , enabled studies that showed that the nature of the pendant lipid could influence the types of cells that were transfected efficiently. CARTs containing unsaturated lipids exhibited up to 80% transfection of EGFP RNA to lymphocytes …”

Hypoxia/Temperature/pH Triple Stimuli–Responsive Block Copolymers: Synthesis, Self‐Assembly, and Controlled Drug Release

“…sites such as tumors, microenvironment acidification is caused, the application of amino and tertiary amines in the field of drug carriers are promising. [43][44][45] Lang and co-workers successfully grafted amine-terminated ploy(N-isopropylacrylamide) onto poly(2-oxepane-1,5-dione-co-ɛ-caprolactone) to achieve the selfassembled core-shell micelles with biodegradability, thermal response, and pH-response properties. [46] Chen et al successfully developed poly(ethylene glycol)-b-(poly(2-(diethylamino)ethyl methacrylate)-b-poly(hydroxyethyl methacrylate)-g-folic acid) 2 [PEG-b-(PDEAEMA-b-PHEMA-g-FA) 2 ] as a drug carrier, and achieved pH responsiveness owing to the protonation of the tertiary amino groups under acidic conditions.…”

Charge-altering releasable transporters enable phenotypic manipulation of natural killer cells for cancer immunotherapy

“…38,39 CARTs are multiblock oligomers consisting of $1 lipid block and a charge-altering block. [38][39][40][41][42][43][44][45] Differing from persistently charged nonviral vectors, CARTs are initially cationic to complex polyanionic nucleic acids but biodegrade under physiological conditions (pH 7.4) to neutral products, facilitating the release of the anionic cargo. 39,44 Here, we demonstrate that CARTs efficiently transfect resting primary human NK cells with messenger RNA (mRNA).…”