Thermally-controlled spherical peptide gel architectures prepared using the pH switch method

Self-assembling nanostructured peptide gels are promising materials for sensing, drug delivery, and energy harvesting. Of particular interest are short diphenylalanine (FF) peptides modified with 9-fluorenylmethyloxycarbonyl (Fmoc), which promotes the association of the peptide building blocks. Fmoc-FF gels generally form fibrous networks and while other structures have been demonstrated, further control of the gelation and resulting ordered three-dimensional structures potentially offers new possibilities in tissue engineering, sensing, and drug release applications. Herein, we report that the structure tunability of Fmoc-FF gels can be achieved by controlling the water content and the temperature. We further explore the incorporation of metal nanoparticles in the formation of the gel to enable optical sensing applications based on hybrid Fmoc-FF-nanoparticle microspheres. Finally, fluorescence lifetime imaging microscopy reveals a correlation between lifetime and reduced bandgap, in support of a semiconductor-induced charge transfer mechanism that might also increase the stability of an excited state of a probe molecule. The observations potentially further widen the use of these peptide materials in bioimaging and sensing applications.