Cyclization and thermal modulation of a β-hairpin peptide for efficient cellular delivery.

Herein, we report Cyc-SVS1, an exceptionally stable and highly efficient cyclic cell penetrating peptide whose sequence is derived from an amphiphilic peptide. Instead of self-assembling to form a gel network, the peptide undergoes a thermally induced folding transition forming a cyclic β-hairpin conformation at 37 °C that can engage cellular membranes effecting rapid cellular entry. This unique temperature-reversible transition allows modulation of peptide membrane binding and cellular entry via thermally controlled folding. Molecular simulations demonstrate the energetic importance of conformation for cyclic CPP membrane engagement. Cyc-SVS1 enables the efficient intracellular delivery of a diverse range of biomacromolecules-including GFP, single-stranded DNA, and plasmids-in cultured cells, underscoring its significant potential for biomedical applications. Finally, it's in vivo delivery efficacy was demonstrated through the successful delivery of siRNA targeting cyclin B1, resulting in the suppression of tumor growth in a HeLa cell xenograft tumor model.