Native chemical ligation directed peptide self assembly

Abstract

This study reports the design and synthesis of peptide gels using an oxo-ester-mediated native chemical ligation (NCL) strategy. The approach involves chemo-selective coupling of N-terminal cysteine-containing peptides with C-terminal fluorophenyl esters—specifically, 4-(trifluoromethyl)phenol and 2,3,4,5,6-pentafluorophenol which were successfully incorporated into peptide segments. The ligation reactions proceeded efficiently in aqueous conditions, without requiring external thiol catalysts or protecting groups. Confocal laser scanning microscopy (CLSM) revealed that the resulting ligated peptides formed entangled nanofibrous networks, creating continuous gel matrices stabilized by covalent and non-covalent interactions such as hydrogen bonding and hydrophobic effects. Rheological analysis confirmed desirable viscoelastic properties, including shear-thinning and thixotropic behavior, with excellent recovery under cyclic stress—highlighting their suitability for injectable and dynamic biomedical applications. Spectroscopic analyses provided further insight into the assembly process—FTIR and circular dichroism (CD) confirmed β-sheet-rich hydrogen-bonded structures, fluorescence spectroscopy demonstrated the importance of hydrophobic interactions, and NMR verified the chemical integrity of the ligated peptides. Overall, this work establishes oxo-ester-mediated NCL as a versatile platform for constructing peptide-based nanomaterials. The combination of synthetic control, spontaneous self-assembly, and tunable mechanical properties offer significant potential for the development of next-generation biomaterials for therapeutic, regenerative, and diagnostic applications.