Polymeric Micelles with pH-Responsive Cross-Linked Core Enhance In Vivo mRNA Delivery

Abstract

Messenger RNA (mRNA) is emerging as a promising therapeutic modality for a variety of diseases. Because of the fragility and limited intracellular access of mRNA, the development of delivery technologies is essential for promoting the applicability of mRNA-based treatments. Among effective nanocarriers, polymeric micelles loading mRNA by polyion complex (PIC) formation with block catiomers have the potential to meet the delivery needs. Since PICs are relatively unstable in in vivo settings, herein, we constructed mRNA-loaded micelles having pH-responsive cross-linked cores by complexing mRNA with cis-aconitic anhydride-modified poly(ethylene glycol)-poly(l-lysine) (PEG-pLL(CAA)) block copolymers. The micelles were stable at physiological pH (pH 7.4) but achieved the complete release of the mRNA at endosomal pH (pH 5.5–4.5). The cross-linking also enhanced the stability of the micelles against disassembly from polyanions and protected the loaded mRNA from degradation by nucleases. Thus, the cross-linked micelles increased the delivery of mRNA to cancer cells, promoting protein expression both in vitro and in vivo. Our results highlight the potential of PEG-pLL(CAA)-based micelles for mRNA delivery.

Polymer‐Based mRNA Delivery Strategies for Advanced Therapies

“…Thus, the cross‐linked micelles showed improved fluc expression in vivo in CT 26 tumor‐bearing mice compared to non‐cross‐linked micelles and even to standard PEI‐based polyplexes (Figure 4c,d) (Table 3). [ 123 ] Besides cross‐linking of polymers, polymer/mRNA crosslinking may provide a prominent stabilizing effect on mRNA. Thus, an ATP‐responsive polymer/mRNA cross‐linked system was proposed for further core stabilization [ 112d ] (Table 3).…”

“…(a–d) Reproduced with permission. [ 123 ] Copyright 2022, MDPI. e) ATP‐responsive bridging between block copolymers and mRNA.…”

“…[117] Copyright 2023, Taylor & Francis. [123] Copyright 2022, MDPI. e) ATP-responsive bridging between block copolymers and mRNA.…”

“…d) Bioluminescence images 9 h postinjection following in vivo delivery of naked mRNA, PEG-pLL/m, PEG-pLL(CAA)/m in CT26 tumor-bearing mice. (a-d) Reproduced with permission [123]. Copyright 2022, MDPI.…”

Novel Vectors and Administrations for mRNA Delivery

“…[154] Yang et al constructed mRNA-loaded micelles with pH-responsive crosslinked cores by complexing mRNA with cis-aconitic anhydridemodified poly(ethylene glycol)-poly(l-lysine) block copolymers (Figure 11B). [155] Su et al developed biodegradable core-shell structured nanoparticles with a poly(𝛽-amino-ester) (PBAE) core enveloped by a phospholipid bilayer shell, and pH-responsive PBAE components can effectively promote the destruction of en-dosomes (Figure 11C). [156] To sum up, pH-responsive vectors can realize intelligent and controllable delivery of mRNA at three levels of organs, tissues, and subcellular compartments.…”