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. Author manuscript; available in PMC: 2009 Sep 3.
Published in final edited form as: Biomaterials. 2008 May;29(13):2015–2024. doi: 10.1016/j.biomaterials.2007.12.049

Figure 1. Two photon excited fluorescence spectra of silk biomaterials.

Figure 1

The spectral features of TPEF fluorescence resulting from 800 nm excitation of silk biomaterials are sensitive to silk II content and protein hydration. (A) The TPEF spectrum of an aqueous 8% silk solution becomes increasingly blue shifted during gelation induced by addition of HCL. Spectra at 6 and 12 hours of gelation overlap significantly. (A, Inset) A blue shift is also observed in the spectra of HFIP-processed films following b sheet induction by methanol treatment. (B) The main structural changes that are thought to contribute to the observed blue shift in panel (A) are depicted schematically. (C) A blue shift in the TPEF emission spectra is observed with decreased protein hydration. (D) The structural changes that are expected to accompany the level of exposure to a polar water environment are depicted for the transition from silk solution to silk film and from hydrated to dehydrated scaffold. (E) FTIR spectra reveal β sheet content. (F) Fluorescence intensity ratios of silk biomaterials.