Interactions of betainium and imidazolium-based ionic liquids with peptide amphiphiles and their implications in the formation of nanohybrid composite gels

Abstract

Ionic liquids (ILs) have been gaining widespread attention due to their plethora of applications. In particular, increasing studies are being carried out to enhance the biological applications of ILs. In this work, a newly synthesized peptide amphiphile comprised of tert-butyl (6-amino-1-((6-aminohexyl) amino)-1-oxohexan-2-yl) carbamate (TAOC) was conjugated with the peptide segment derived from laminin, YIGSR, and self-assembled to form nanofibers. The formed nanofibers were then blended with two separate ionic liquids, betainium bis(trifluoromethylsulfonyl)imide [Hbet][NTf2] and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C4mim][NTf2] to form nanohybrids. To the nanohybrids, collagen (Type IV) was incorporated to further enhance biocompatibility. Our results indicated that the imidazolium-based nanohybrids formed globular assemblies and displayed higher thermal stability and mechanical strength compared to [Hbet][NTf2]-based nanocomposites. The binding interactions with the ionic liquids were probed by FTIR spectroscopy, DSC, TGA as well as predictive COSMO-RS studies, which indicated the key role of hydrogen bonding and hydrophobic interactions. Cell studies with neural cortical cells revealed that in both cases, the nanohybrids reduced cytotoxicity compared to the neat ionic liquids. Furthermore, axonal growths were observed. Such ionic liquid infused peptide nanohybrids, particularly the imidazolium-based nanohybrid gels may have potential for biological applications.