Divergent Supramolecular Gelation of Backbone Modified Short Hybrid δ-Peptides

The ordered supramolecular assemblies of short peptides have been recently gaining momentum due to their widespread applications in biology and materials sciences. In contrast to the α-peptides, limited success has been achieved from the backbone modified peptides. The proteolytic stability and conformational flexibility of the backbone modified peptides composed of β-, γ-, and δ-amino acids can be explored to design ordered supramolecular gels and self-assembled materials. In this article, we are reporting the divergent supramolecular gels from a new class of short hybrid dipeptides composed of conformationally flexible new β(O)-δ⁵-amino acids. The hybrid dipeptide composed of β³- and β(O)-δ⁵-Phe showed the formation of transparent gels from the aromatic solvents, while the dipeptide composed of β(O)-δ⁵-Phe showed the thixotropic gel in phosphate buffered saline (PBS). In contrast, no organic or hydrogels were observed from the dipeptides composed of alternating α- and β(O)-δ⁵-Phe as well as γ⁴ and β(O)-δ⁵-Phe. The organogelation property displayed by the β³,β(O)-δ⁵-Phe dipeptide was further explored to recover the oil spills from the oil-water mixture. The thixotropic hydrogels displayed by the β(O)-δ⁵, β(O)-δ⁵-Phe dipeptide was further utilized as matrix along with cell culture medium to grow the cells in 2D-cell culture. Replacing the backbone -CH₂- with "O" in the δ-Phe leads to the drastic change in the supramolecular behavior of δ-peptides. Overall, the short dipeptides from different backbone modified amino acids showed the divergent gelation properties and these properties can be further explored to design new functional biomaterials.