FRET-Paired Hydrogel Forming Silk-Elastin-Like Recombinamers by Recombinant Conjugation of Fluorescent Proteins

In the last decades, recombinant structural proteins have become very promising in addressing different issues like the lack of traceability of biomedical devices or the design of more sensitive biosensors. Among them, we find elastin-like recombinamers (ELRs), which can be designed to self-assemble into diverse structures, like hydrogels. Furthermore, they might be combined with other protein polymers, such as silk, to give silk-elastin-like recombinamers (SELRs), holding the properties of both proteins. In this work, due to their recombinant nature, we have fused two different fluorescent proteins (FPs), i.e. the green Aequorea coerulescens EGFP and the near-infrared eqFP650, to a SELR able to form irreversible hydrogels through physical cross-linking. These recombinamers showed an emission of fluorescence similar to the single FPs, and they were capable of forming hydrogels with different stiffness (G’ = 60-4000 Pa), by varying the concentration of the SELR-FPs. Moreover, the absorption spectrum of SELR-eqFP650 showed a peak greatly overlapping the emission spectrum of the SELR-