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Supercritical CO2 was used as an antisolvent to form protein particles that exhibited minimal loss of activity upon reconstitution. Organic protein solutions were sprayed under a variety of operating conditions into the supercritical fluid, causing precipitation of dry, microparticulate (1-5 microns) protein powders. Three proteins were studied: trypsin, lysozyme, and insulin. Amide I band Raman spectra were used to estimate the alpha-helix and beta-sheet structural contents of native and precipitate powders of each protein. Analysis of the Raman spectral revealed minimal (lysozyme), intermediate (trypsin), and appreciable (insulin) changes in secondary structure with respect to the commercial starting materials. The perturbations in secondary structure suggest that the most significant event during supercritical fluid-induced precipitation involved the formation of beta-sheet structures with concomitant decreases of alpha-helix. Amide I band Raman and Fourier-transform infrared (FTIR) spectra indicate that higher operating temperatures and pressures lead to more extensive beta-sheet-mediated intermolecular interactions in the precipitates. Raman and FTIR spectra of redissolved precipitates are similar to those of aqueous commercial proteins, indicating that conformational changes were reversible upon reconstitution. These results suggest that protein precipitation in supercritical fluids can be used to form particles suitable for controlled release, direct aerosol delivery to the lungs, and long-term storage at ambient conditions.

ence electrodes. Films were inserted into a home-built sample holder, with an air-filled gas-phase volume of 0.326 cm 3 encapsulated between the electrode and the polymer film/glass substrate using a 20 mm diameter Viton O'-ring spacer. Six UVA 365 ± 25 nm fluorescent tubes (8W BLB, I = 5.96 mW cm ±2 ) arranged in a semicircle and placed 13 cm above the cell, facing the cell, were used as the irradiation source, resulting in a sample irradiance of 4.8 mW cm ±2 , similar to the intensity of UVA solar irradiance. A fan was used to prevent the cell from heating up due to the heat from the irradiation source. SEM images were obtained with a Philips XL-30 field-emission scanning electron microscope. Samples were coated with Au/Pd prior to observation. For TAS measurements, a PTI GL-3300 N 2 -laser (337 nm, 30 lJ cm ±2 , repetition rate of 0.8 Hz) was used as the excitation source [5]. X-ray diffraction analysis of the Degussa P25 and P90 materials showed that both materials consist of TiO 2 anatase and rutile particles, the anatase contents being 81 % and 90 % for P25 and P90, respectively. The crystal domain size of the anatase particles was estimated as 20 nm for TiO 2 P25 and 13 nm for TiO 2 P90.

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Mesoporous silica materials with pore structures such as 2D hexagonal close packed, bicontinuous cubic, lamellar, sponge, wormhole-like, and rectangular have been made by using surfactant templating sol-gel processes. However, there are still some "intermediate" phases, in particular mesh phases, that are formed by surfactants but which have not been made into analogous silica pore structures. Here, we describe the one-step synthesis of mesoporous silica with a mesh phase pore structure. The cationic fluorinated surfactant 1,1,2,2-tetrahydroperfluorodecylpyridinium chloride (HFDePC) is used as the template. Like many fluorinated surfactants, HFDePC forms intermediate phases in water (including a mesh phase) over a wider range of compositions than do hydrocarbon surfactants. The materials produced by this technique are novel elongated particles in which the layers of the mesh phase are oriented orthogonal to the main axis of the particles.