Fig. 3.

Non-viral carrier system for delivery of modified mRNA. Since mRNAs are large, hydrophilic, negatively charged molecules, entering the cell is challenging. Therefore, various carrier systems have been developed to improve cellular uptake and protecting the mRNA from degradation. Lipid-based delivery represents the most commonly applied technique to facilitate cellular entry. In addition, positively charged peptides can be used for complexation of mRNA, enabling access to the cell via an endocytotic mechanism. Similarly, polymers like polyethylenimine, polylactide-co-glycolide, polyamidoamine have been utilized to encapsulate mRNA molecules before cellular transfection. Novel delivery concepts aim to exploit the benefits of existing carrier systems by a combination of nanoparticles, lipids and proteins leading to hybrid nanoparticles.