75bar). 2.5. Scanning Electron Microscopy The morphological characteristics of SF microparticles and cross-sections of Gelatin/SF blends, both before and after treatment with dehydrating solvents and before and after drug release experiments, were examined by scanning electron microscopy (SEM). Samples of dried films were prepared

for SEM imaging Inhibitors,research,lifescience,medical by flash freezing in liquid nitrogen and immediately fracturing with a sharp blade to produce cross-sections. The samples were then coated with a ~8nm layer of Au/Pt mist using a sputter coater. A Hitachi S3200 variable pressure scanning electron microscope equipped with an E-T secondary electron detector was used to examine the samples at an accelerating voltage of 5kV and a working distance of 15mm. 2.6. Dynamic Light Scattering Particle size measurements for silk microparticles were also performed using dynamic light scattering (DLS). A Nicomp ZW380 (Particle Sizing systems, Inc. Ca) particle sizer at fixed angle (90°) and 632.8nm was employed for size Inhibitors,research,lifescience,medical distribution measurements. The SF microparticles were suspended in an oil matrix at a 1:100 dilution before measurements. 2.7. Infrared Spectroscopy FTIR spectra of silk fibroin blend films were collected using a Nicolet 510P spectrometer equipped with the NLG919 mouse attenuated total reflectance (ATR) accessory. These films were cast on the surface of polystyrene weigh boats directly from Inhibitors,research,lifescience,medical solution.

Each spectrum for samples was acquired in transmittance mode with a spectral range of 4000–400cm−1. FTIR spectra of the SF-containing microparticles were collected using a Perkin-Elmer Spectrum BX FTIR spectrophotometer and NIC380 Avatar OMNI Sampler apparatus. KBr pellets, containing ~0.7% (w/w) of spray-dried powder were prepared using a Carver Pellet Press with 18,000 lbs applied load. Thin Inhibitors,research,lifescience,medical films for Inhibitors,research,lifescience,medical comparison were obtained by casting of SF solution on the surface of polystyrene weigh boats and were analyzed by FTIR. 2.8. In Vitro Drug Release Studies The naproxen release from the films, matrixes, and spray-dried microparticles was

studied using Distek Evolution 6100 dissolution system. Two sets of conditions were used: one-stage method with apparatus 2 (paddle) at 50rpm in 500mL of pH 7.4 phosphate buffer at 37°C and three-stage method with three pH buffers—simulated gastric fluid (pH 1.2), simulated intestinal fluid (pH 4.8) and pH 7.4 buffer. The samples (1.5mL) at each predetermined time point were analyzed by HPLC according to naproxen sodium, USP method. The Astemizole detector wavelength was set at 272nm and the injection volume was 10μL. The HPLC column used was Inertsil ODS-3 4.6 × 250mm, 5μm with the column temperature maintained at 25°C. The mobile phase was a binary mixture of potassium phosphate buffer:acetonitrile (3:2) at pH 3.0 pumped at flow rate of 1.5mL/min. 3. Results 3.1. Silk Fibroin Processing Raw silk consists of fibroin that is bound together by hydrophilic gum-like protein, the sericin.