STRUCTURE OF SILK FIBROIN NANOPARTICLES: CHARACTERIZATION OF HYDROPHOBIC PATCHES

Nanoparticles are extensively used in various areas of industry. Among different nanoparticles, protein nanoparticles complexed with a wide range of drugs have a great potential for biomedical applications. Silk fibroin exhibits good biocompatibility properties and, therefore, is a good raw material for a wide variety of applications. In this study, structure and hydrophobic patch formation were studied in nanoparticles fabricated from silk fibroin. Far-UV circular dichroism spectroscopy and birefringence observed in a polarized microscope with Congo red staining indicate that fibroin nanoparticles are composed of small amyloid domains. Steady-state and time-resolved fluorescence of ANS revealed two hydrophobic patch formations. Decay-associated spectra of ANS bound to these patches show two species with lifetimes of about 4.2 ns and 14.8 ns. Dissociation constants for ANS complex formation for these patches are 8.3±0.4 M and 5.9±0.3 M, respectively. Acrylamide fluorescence quenching shows that solvent accessibility to native Trp residues is significantly decreased during fibroin nanoparticle formation. Data indicate that nanoparticles fabricated from fibroin are a good candidate for drug delivery applications.