Thermally Induced Structural Transition of Peptide Nanofibers into Nanoparticles with Enhanced Fluorescence Properties

A heating treatment method for the synthesis of fluorescent nanoparticles using simple N-(9-fluorenylmethoxycarbonyl) (Fmoc)-protected tripeptides is reported. Two pairs of Fmoc-protected tripeptides (Fmoc-FR₁ R₂ , R₁ =F or W, R₂ =H or Y) were designed by changing the amino acid sequences of the peptides. The peptides can self-assemble into nanofibers at lower temperatures, which will spontaneously transform into fluorescent nanoparticles under heating treatment. Moreover, the fluorescence properties of the self-assembled structures can be affected by changing amino acids in the middle of the tripeptide. Specifically, tryptophan (W) can promote fluorescence of the assemblies incubated at high temperatures. Thus, the temperatures and amino sequences of the Fmoc-protected tripeptides have significant effects on the fluorescence of the assembled nanostructures. The results provide a design principle for self-assembled fluorescent peptide nanostructures with potential biomedical applications.