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

Abstract

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.

Effect of Imposing Spatial Constraints on Low Molecular Weight Gels

“…18−21 For example, Huang et al and Almohammed et al demonstrated that it was possible to achieve distinct microstructures comprising completely different morphologies in materials produced from the same gelators by changes in temperature. 15,22,23 This was built upon by Chen et al and Dudukovic et al, who both demonstrated that microstructure morphology could be altered by varying solvent ratios within a solvent-switch gelation trigger (Figure 1a). 6,16 These studies support the aforementioned key idea that gelation within this class of materials is affected by a vast range of variables.…”

“…Changing the building blocks from which the gels are formed results in a different material. Potentially less intuitive is the ability to form materials from the same gelator through altering the preparation process, leading to gels presenting distinct mechanical, or other, properties. ,− It has been demonstrated that different gelation triggers as well as modifications to or variations within the same trigger can all lead to distinct materials being produced from the same starting gelators. ,,− ,− Often this is due to subtle changes to the underlying solid-like gelator network and the microstructure it presents. − For example, Huang et al and Almohammed et al demonstrated that it was possible to achieve distinct microstructures comprising completely different morphologies in materials produced from the same gelators by changes in temperature. ,, This was built upon by Chen et al and Dudukovic et al, who both demonstrated that microstructure morphology could be altered by varying solvent ratios within a solvent-switch gelation trigger (Figure a). , These studies support the aforementioned key idea that gelation within this class of materials is affected by a vast range of variables.…”