Stabilizing Scaffold for Short Peptides Based on Knottins

Background: Bombesin (BBN) is a short peptide with a high affinity for receptors that are expressed on the surface of various types of cancer cells. However, a full length BBN molecule has low in vivo stability. Objective: In our study, we propose the use of peptide toxins, derived from animal and plant toxins, as scaffold molecules to enhance the bioavailability and stability of bombesin. These peptides possess a unique structure known as an inhibitory cystine knot. Methods: We synthesized structures in which short bombesin was incorporated into various domains of arthropod and plant toxins using solid-phase peptide synthesis. The stability under different conditions was assessed through high-performance liquid chromatography, and binding to cell cultures expressing the bombesin receptor was analyzed. Additionally, toxicity to cell cultures was evaluated using fluorescence microscopy. Results: The data obtained demonstrated that placing the short peptide between the first and second cysteine residues in arachnid toxins results in increased in vitro stability and bioavailability, as well as low cytotoxicity. Conclusion: Arachnid toxins with an inhibitory cystine knot can be considered as a scaffold for increasing the stability of therapeutic peptides.