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Combinatorial optimization of PEG architecture and hydrophobic content improves siRNA polyplex stability, pharmacokinetics, and potency in vivo

Author:
Werfel, Thomas A., Jackson, Meredith A., Kavanaugh, Taylor E., Kirkbride, Kellye C., Miteva, Martina, Giorgio, Todd D., Duvall, Craig
Source:
Journal of Controlled Release 2017
ISSN:
0168-3659
Subject:
biocompatibility, blood circulation, chemical bonding, gene silencing, genes, hydrophobicity, intravenous injection, luciferase, models, nanomedicine, pH, pharmacokinetics, polyethylene glycol, renal clearance, small interfering RNA
Abstract:
A rationally-designed library of ternary siRNA polyplexes was developed and screened for gene silencing efficacy in vitro and in vivo with the goal of overcoming both cell-level and systemic delivery barriers. [2-(dimethylamino)ethyl methacrylate] (DMAEMA) was homopolymerized or colpolymerized (50mol% each) with butyl methacrylate (BMA) from a reversible addition – fragmentation chain transfer (RAFT) chain transfer agent, with and without pre-conjugation to polyethylene glycol (PEG). Both single block polymers were tested as core-forming units, and both PEGylated, diblock polymers were screened as corona-forming units. Ternary siRNA polyplexes were assembled with varied amounts and ratios of core-forming polymers to PEGylated corona-forming polymers. The impact of polymer composition/ratio, hydrophobe (BMA) placement, and surface PEGylation density was correlated to important outcomes such as polyplex size, stability, pH-dependent membrane disruptive activity, biocompatibility, and gene silencing efficiency. The lead formulation, DB4-PDB12, was optimally PEGylated not only to ensure colloidal stability (no change in size by DLS between 0 and 24h) and neutral surface charge (0.139mV) but also to maintain higher cell uptake (>90% positive cells) than the most densely PEGylated particles. The DB4-PDB12 polyplexes also incorporated BMA in both the polyplex core- and corona-forming polymers, resulting in robust endosomolysis and in vitro siRNA silencing (~85% protein level knockdown) of the model gene luciferase across multiple cell types. Further, the DB4-PDB12 polyplexes exhibited greater stability, increased blood circulation time, reduced renal clearance, increased tumor biodistribution, and greater silencing of luciferase compared to our previously-optimized, binary parent formulation following intravenous (i.v.) delivery. This polyplex library approach enabled concomitant optimization of the composition and ratio of core- and corona-forming polymers (indirectly tuning PEGylation density) and identification of a ternary nanomedicine optimized to overcome important siRNA delivery barriers in vitro and in vivo.
Agid:
5663687