Co-delivery of different species of protein-encoding polynucleotides, e.g., messenger RNA
(mRNA) and plasmid DNA (pDNA), using the same nanocarrier is an interesting topic that remains
scarcely researched in the field of nucleic acid delivery. The current study hence aims to explore the
possibility of the simultaneous delivery of mRNA (mCherry) and pDNA (pAmCyan) using a single
nanocarrier. The latter is based on gelatin type A, a biocompatible, and biodegradable biopolymer of
broad pharmaceutical application. A core-shell nanostructure is designed with a thermally stabilized
gelatin–pDNA coacervate in its center. Thermal stabilization enhances the core’s colloidal stability
and pDNA shielding effect against nucleases as confirmed by nanoparticle tracking analysis and gel
electrophoresis, respectively. The stabilized, pDNA-loaded core is coated with the cationic peptide
protamine sulfate to enable additional surface-loading with mRNA. The dual-loaded core-shell
system transfects murine dendritic cell line DC2.4 with both fluorescent reporter mRNA and pDNA
simultaneously, showing a transfection efficiency of 61.4 ± 21.6% for mRNA and 37.6 ± 19.45% for
pDNA, 48 h post-treatment, whereas established commercial, experimental, and clinical transfection
reagents fail. Hence, the unique co-transfectional capacity and the negligible cytotoxicity of the
reported system may hold prospects for vaccination among other downstream applications