Rhodamine binds to silk fibroin and inhibits its self-aggregation

Silk Fibroin‐Based Films Enhance Rhodamine 6G Emission in the Solid State: A Chemical–Physical Analysis of their Interactions for the Design of Highly Emissive Biomaterials

“…Interestingly, when SF:RHD films were subjected to repeated alcohol spray treatment for at least 2 h, an aggregated β‐sheet structure was not observed, at variance with the behavior of pristine SF films. Altogether FTIR data clearly show that RHD inhibits the formation of intermolecular β‐sheet aggregates, consistent with our previous findings on the role of RHD in preserving, in solution, non aggregated SF …”

“…The fibroin extract was then rinsed three times in Milli‐Q water, dissolved in 9.3 m LiBr solution at room temperature, and set covered within a 60 °C oven for 4 h. The solution was then dialyzed in phosphate buffer 30 m m , pH 7.5 for 24 h. The dialyzed silk solution was then centrifuged for 10 min at 9000 rpm, and the supernatant was collected and stored at 4 °C. The final concentration of aqueous silk solution was 86 µ m , as determined by UV absorption using extinction coefficient ε 275nm = 1.064 cm −1 mg −1 mL . The films were obtained by slow evaporation of 400 µL SF solutions, deposited on polystyrene substrates, without and with different amounts of RHD 6G (Sigma‐Aldrich N°252433).…”

“…Pristine aqueous 400 µ m RHD, corresponding to the RHD concentration in the SF:RHD 1:5 sample, was employed based on previous results, showing that a stoichiometry of five was observed in solution for RHD binding to SF.…”

“…We have demonstrated that quenching effects, caused by the aggregation of pristine RHD in solution, can be efficiently reduced by encapsulating the monomeric RHD dye within a protein cavity, forming a water‐soluble host−guest complex . We have further shown that RHD, establishing specific interactions with SF in solution, is capable of inhibiting protein self‐association, thus controlling β‐conformational transition . Now, the aim of the present paper is to investigate the physical–chemical properties of cast films, obtained by slow evaporation of SF solutions in the presence of different concentrations of RHD.…”

“…[15] We have further shown that RHD, establishing specific interactions with SF in solution, is capable of inhibiting protein self-association, thus controlling β-conformational transition. [16] Now, the aim of the present paper is to investigate the physical-chemical properties of cast films, obtained by slow evaporation of SF solutions in the presence of different concentrations of RHD. Indeed SF films have been reported to display high transparency (approx.…”