Rational Design of Amphiphilic Fluorinated Peptides: Evaluation of Self-Assembly Properties and Hydrogel Formation

Advanced peptide-based nanomaterials composed of self-assembling peptides (SAPs) gain an emerging interest in pharmaceutical and biomedical applications. The introduction of fluorine into peptides, in fact, offers unique opportunities to tune their biophysical properties and intermolecular interactions. In particular, the degree of fluorination plays a crucial role in peptide engineering as it can be used to control the intensity of fluorine-specific interactions. Here, we designed and explored a series of amphipathic self-assembling peptides by incorporating the fluorinated amino acids (2S)-4-monofluoroethylglycine (MfeGly), (2S)-4,4-difluoroethylglycine (DfeGly) and (2S)-4,4,4-trifluoroethylglycine (TfeGly) as main components. This approach enabled studying the impact of fluorination on secondary structure formation and peptide self-assembly on a structural basis. We show that the interplay between polarity and hydrophobicity, both induced by varying degrees of side chain fluorination, affects peptide folding and leads to the generation of peptide hydrogels composed of fluorinated aliphatic amino acids. Molecular simulations revealed the formation of electrostatically driven intra-chain and inter-chain contact pairs caused by side chain fluorination. Our study provides a systematic report about the distinct features of fluorinated oligomeric peptides with potential applications as peptide-based biomaterials.