mRNA lipid nanoparticles (LNPs) are at the forefront of nucleic acid intracellular delivery, as exemplified by the recent emergency approval of two mRNA LNP-based COVID-19 vaccines. The success of an...
In recent years, there has been an
increasing interest in designing
delivery systems to enhance the efficacy of RNA-based therapeutics.
Here, we have synthesized copolymers comprised of dimethylaminoethyl
methacrylate (DMAEMA) or diethylaminoethyl methacrylate (DEAEMA) copolymerized
with alkyl methacrylate monomers ranging from 2 to 12 carbons, and
developed a high throughput workflow for rapid investigation of their
applicability for mRNA delivery. The structure activity relationship
revealed that the mRNA encapsulation efficiency is improved by increasing
the cationic density and use of shorter alkyl side chains (2–6
carbons). Minimal cytotoxicity was observed when using DEAEMA-co-BMA (EB) polyplexes up to 18 h after dosing, independent
of a poly(ethylene glycol) (PEG) first block. The lowest molecular
weight polymer (EB10,250) performed best, exhibiting greater transfection
than polyethyenimine (PEI) based upon the number of cells transfected
and mean intensity. Conventional investigations into the performance
of polymeric materials for mRNA delivery is quite tedious, consequently
limiting the number of materials and formulation conditions that can
be studied. The high throughput approach presented here can accelerate
the screening of polymeric systems and paves the way for expanding
this generalizable approach to assess various materials for mRNA delivery.
Block copolymers consisting of blocks of poly(amino acid)s (PAAs) derived from naturally occurring L-amino acids and biocompatibilizing poly(ethylene glycol) (PEG) are of interest for biomedical applications because of their compatibility, partial degradability, and, depending on their molecular architecture, unique self-assembly behavior. PEGylated PAAs were synthesized by α-methoxy-ω-amino PEG-initiated ring-opening polymerization, ROP, of the Ncarboxyanhydrides, NCAs, of L-leucine and L-glutamic acid γ-benzyl ester. The molecular weights of the resulting di-and triblock copolymers were well controlled with narrow polydispersities, and the block copolymers were obtained in high yields (>90 %). PEGylated PAA diblock copolymers with a copolymer block of PAAs were obtained when the amino acid NCAs were polymerized as a mixture and triblock copolymers with two PAA hompolymer blocks resulted from the successive addition of the respective NCAs. Dynamic light scattering indicated that these block copolymers self-assemble when exposed to a selective solvent into micelles with hydrodynamic radii between 7 and 10 nm, which aggregate into larger structures with radii ranging between 27 and 40 nm. The coexistence and sizes of the two types of particles were corroborated by small-angle neutron scattering analyses. A detailed analysis of the micelle core structures by transmission electron microscopy suggests that the cores of the micelles do not form perfect spheres and thereby enable their continued aggregation, which is further aided by the immiscibility and subsequent phase separation of poly(L-glutamic acid γ-benzyl ester) and poly(L-leucine) blocks that constitute the PAA block.
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