Hybrid vectors are a remarkable strategy to address the current challenges in gene delivery.

We discovered a new class of artificial peptidic transfection vectors based on an artificial anion-binding motif, the guanidiniocarbonylpyrrole (GCP) cation. This new type of vector is surprisingly smaller than traditional systems, and our previous work suggested that the GCP group was important for promoting critical endosomal escape. We now present here a systematic comparison of similar DNA ligands featuring our GCP oxo-anion-binding motif with DNA ligands only consisting of naturally occurring amino acids. Structure-activity studies showed that the artificial binding motif clearly outperformed natural amino acids such as histidine, lysine, and arginine. It improved the ability to shuttle foreign genetic material into cells, yet successfully mediated endosomal escape. Also, plasmids that were complexed by our artificial ligands were stabilized against cytosolic degradation to some extent. This resulted in the successful expression of plasmid information (comparable to gold standards such as polyethyleneimine). Hence, our study clearly demonstrates the importance of the tailor-made GCP anion-binding site for efficient gene transfection.

The cover feature shows that three‐armed cationic peptide ligands are efficient gene transfection vectors. However, only when they contain an artificial oxoanion binding site, the GCP group, in their arms. Ligands with arginine, lysine or histidine instead show no transfection. In our paper we analyse the reason for this behaviour. More information can be found in the full paper by C. Schmuck et al. on page 2268 in Issue 22, 2017 (DOI: 10.1002/cbic.201700433).