A simple epoxide modification strategy to construct amino-functional poly(2-oxazoline) mRNA delivery vectors

Messenger RNA (mRNA) delivery vectors are pivotal in the realm of vaccines and gene therapy. While polymer-based delivery vectors have garnered growing interest owing to their tunable structures and favorable biocompatibility, achieving high delivery efficiency remains a critical challenge. Poly(2-oxazoline) (POx) emerges as a promising candidate in biomedicine, yet its exploration in mRNA delivery is nascent. Herein, we engineered poly[2-(5-aminopentyl)-2-oxazoline]-based (PAmOx) polymers as efficient mRNA delivery vectors through a straightforward one-step ring-opening reaction between the amino group on the PAmOx and the epoxide molecules. We conducted a systematic examination of how the degree of polymerization and the nature of grafted epoxide molecules influence mRNA delivery efficiency. <i>In vitro</i> experiments demonstrated that DP50-PE6, synthesized <i>via</i> a ring-opening reaction between 1,2-epoxydecane (E6) and PAmOx₅₀, enhanced mRNA transfection efficiency by a staggering 3.3 × 10⁵-fold compared with the parent PAmOx₅₀. Consistent with the <i>in vitro</i> findings, <i>in vivo</i> intramuscular administration of the DP50-PE6/mRNA complex exhibited robust expression at the site of injection (1.8 × 10⁶ p/sec/cm²/sr) and remained detectable for two days. Notably, following intravenous administration, the DP50-PE6/mRNA complex exhibited selective protein expression in the spleen which accounted for approximately 85.1% of the total expression observed across major organs. Further research revealed that the DP50-PE6/mOVA complex, when combined with anti-PD1, effectively inhibited tumor growth in the B16-OVA melanoma model, achieving a tumor suppression rate over 90%. These findings underscore the immense potential of POx-based vectors in mRNA delivery, setting the stage for the evolution of POx-inspired nucleic acid delivery vectors.