Purpose: mRNA has recently emerged as a potent therapeutics and requires safe and effective delivery carriers, particularly prone to address its issues of poor stability and escape from endosomes. In this context, we designed poly(D,L-lactide) (PLA)-based micelles with N-succinimidyl (NS) ester decorated hydrophilic hairy corona to trap/couple a cationic fusogenic peptide and further complex mRNA.
Methods: Two strategies were investigated, namely (i) sequential immobilization of peptide and mRNA onto the micelles (layer-by-layer, LbL) or (ii) direct immobilization of peptide-mRNA pre-complex (PC) on the micelles. After characterization by means of size, surface charge, peptide/mRNA coupling/complexation and mRNA serum stability, carrier cytotoxicity and transfection capacity were evaluated with dendritic cells (DCs) using both GFP and luciferase mRNAs.
Results: Whatever the approach used, the micellar assemblies afforded full protection of mRNA in serum while the peptide-mRNA complex yielded complete mRNA degradation. In addition, the micellar assemblies allowed to significantly reduce the toxicity observed with the peptide-mRNA complex. They successfully transfected hard-to transfect DCs, with a superior efficiency for the LbL made ones (whatever mRNAs studied) showing the impact of the elaboration process on the carrier properties.
Conclusions: These results show the relevance and potential of this new PLA/peptide based micelle platform to improve mRNA stability and delivery, while offering the possibility of further multifunctionality through PLA core encapsulation.
Keywords: Micelles; cationic fusogenic peptide; mRNA delivery; polylactide.