Neuron-Targeted Copolymers with Sheddable Shielding Blocks Synthesized Using a Reducible, RAFT-ATRP Double-Head Agent

Abstract

Successful adaptation of in vitro optimized polymeric gene delivery systems for in vivo use remains a significant challenge. Most in vivo applications require particles that are sterically stabilized but doing so significantly compromises transfection efficiency of materials shown to be effective in vitro. In this communication, we present a multi-functional well-defined block copolymer that forms particles with the following properties: cell targeting, reversible shielding, endosomal release, and DNA condensation. We show that targeted and stabilized particles retain transfection efficiencies comparable to the non-stabilized formulations. The block copolymers are synthesized using a novel, double-head agent (CPADB-SS-iBuBr) that combines a RAFT CTA and an ATRP initiator through a disulfide linkage. Using this double-head agent, a well-defined cationic block copolymer P(OEGMA)15-SS-P(GMA-TEPA)50 containing a hydrophilic oligoethyleneglycol (OEG) block and a tetraethylenepentamine (TEPA)-grafted polycation block was synthesized. This material effectively condenses plasmid DNA into salt-stable particles that deshield under intracellular reducing conditions. In vitro transfection studies showed that the reversibly shielded polyplexes afforded up 10-fold higher transfection efficiencies compared to the analogous stably-shielded polymer in four different mammalian cell lines. To compensate for reduced cell uptake caused by the hydrophilic particle shell, a neuron-targeting peptide was further conjugated to the terminus of theP(OEGMA) block. Transfection of neuron-like, differentiated PC-12 cells demonstrated that combining both targeting and deshielding in stabilized particles yields formulations that are suitable for in vivo delivery without compromising in vitro transfection efficiency. These materials are therefore promising carriers for in vivo gene delivery applications.

Highly branched poly(β-amino ester)s for skin gene therapy

“…In contrast to the viral vectors, non-viral vectors (especially cationic polymers) hold greater promise for clinical application [6][7][8][9]. Effective and safe polymeric vectors with simplicity, scalability, low cost and ease of use are of high clinical significance [10][11][12].…”

Dual Responsive, Stabilized Nanoparticles for Efficient In Vivo Plasmid Delivery

“…[7] Polyplexes that detach the PEG shielding layer in response to signals in the biological microenvironments are an elegant solution to these issues. [8][9][10][11] Biodistribution studies with PEGylated polyplexes have revealed an additional complication: PEGylated polyplexes can exhibit poor stability and premature unpackaging in vivo, likely due to interactions with serum proteins and extracellular matrix components. [12][13][14] Hydrophobic modification of polycations has been explored as a potential solution.…”

Synthesis of multifunctional ABC stars with a reduction-labile arm by consecutive ROP, RAFT and ATRP processes

“…RAFT and ATRP systems have proven to be concurrent or compatible in some cases [48,49]. For instance, Wei et al [48] directly used a reducible RAFT-ATRP double-head agent for RAFT polymerization of oligo(ethylene glycol) monomethyl ether methacrylate (OEGMA) and ATRP of glycidyl methacrylate (GMA) to generate POEGMA-b-PGMA.…”

“…For instance, Wei et al [48] directly used a reducible RAFT-ATRP double-head agent for RAFT polymerization of oligo(ethylene glycol) monomethyl ether methacrylate (OEGMA) and ATRP of glycidyl methacrylate (GMA) to generate POEGMA-b-PGMA. However, the influence of dithiobenzoate on ATRP of tBA lacks systematic research thus far.…”