Nowadays researchers can make synthetic messenger RNAs (mRNAs) that encode for any desired protein. Additionally, small interfering (si)RNAs have been rationally synthetized that specifically inhibit the expression of a selected protein. However, to translate the huge potential of these synthetic RNAs to real applications, efficient carriers that protect and delivery these RNAs inside the cytoplasm of cells are required. This need has resulted in a rush for efficient and patented carriers for siRNAs and especially synthetic mRNAs in recent years. In this project, we aim to further develop our recently discovered, and patented, cationic polymer transfection agents that showed higher efficacy during in vitro transfection of synthetic self-amplifying mRNAs than the current state-of-the-art. Preliminary in vivo transfection data revealed that these agents may also have high potential for in vivo use.