Abstract
The specific delivery of messenger RNA (mRNA) is an excellent alternative to plasmid DNA, due to the latter’s potential risk for random integration into the host genome. In this study, we propose the use of specially tailored polyplex nanomicelles for the intravenous delivery of mRNA into the brain of mice. In brief, along the backbone of a polyaspartamide polymer that is terminated with a 42k Polyethylene glycol chain (PEG), aminoethylene-repeating groups (two, three, and four units, respectively) were conjugated to side-chains to promote electrostatic interactions with mRNA. This structural configuration would ultimately condense into a polyplex nanomicelle ranging between 24 and 34 nm, as was confirmed by transmission electron microscopy (TEM) and dynamic light scattering (DLS) while the chemistry of the synthesis was validated through NMR analysis. Subsequently, we hypothesized an important correlation pertaining to the role of hydrogen bonding between the interaction of polyamine and mRNA in due course. As a proof of concept, we encapsulated the luciferase (Luc2) mRNA as a reporter gene through in vitro transcription (IVT) and subsequently infused the polyplex nanomicelles into mouse brains via an intracerebroventricular (ICV) injection to bypass the blood–brain barriers (BBB). Data revealed that PEGylated polyplex nanomicelles possessing four repeating units of aminoethylene groups had exhibited the best Luc2 mRNA delivery efficiency with no significant immune response registered.
Highlights
While the potency of messenger RNA (mRNA)-based therapeutics is highly undisputed, the mode of delivery is often the main hindering factor for its limited use [1,2]
To demonstrate the reduced systemic immune responses of mRNA in animal administration attributed from nanomicelle protection, we applied naked Luc2 mRNA or nanomicelle-protected Luc2
To further improve on the stability of the overall polymeric complex, polyethylene glycol (PEG) chain with a molecular weight of 42k Dalton was introduced to the C-terminus end of the polyaspartic frame
Summary
While the potency of mRNA-based therapeutics is highly undisputed, the mode of delivery is often the main hindering factor for its limited use [1,2]. By relying on the electrostatic interaction of positively charged amino (NH) moieties and the negatively charged ribonucleotides, mRNA can be condensed to form a polyplex configuration and be subsequently delivered into cellular targets What sets this strategy apart from other conventional linear polyionic complexes is the presentation of the short cationic NH tethers that extend from the side-chains of the polymer rather than incorporating them along the linear backbone of the polymer, and this was found to have substantially lower cytotoxicity compared with other chemical arrangements [11,12]. This report represents one of the early attempts to administer such PEG-based nanocomplex/mRNA hybrid vesicles for the treatment of brain disorders in animal models
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