Microparticle structure

Large control over the release rate by control of the microparticle structure. 

In the first step of the interfacial cross-linking polymerization, the polymer is dissolved into the solvent, which is the internal phase of the emulsion, and another phase with a nonsolvent to the polymer is produced then the aqueous phase is poured to the organic phase to produce the emulsion. Afterwards, a solution containing the cross-linking agent is added to the emulsion to form a rigid structure of the microparticles (Couvreur et al., 2002 Rao Geckeler, 2011). 

F Koosha, RH Muller, SS Davis, MC Davies. The surface chemical structure of poly (/J-hydroxybutyrate) microparticles produced by solvent evaporation process. J Control Rel 9 149, 1989. 

BD Barr-Howell, NA Peppas. Structural analysis of poly(2-hydroxyethyl methacrylate) microparticles. Eur Polym J 23 591-596, 1987. 

Similar structures using a silica-in-carbon core-shell structure have also been synthesized [76], which afford new possibilities for nanoencapsulation. Carbon can be removed by calcination, leaving silica, and (if the positions of silica and carbon are reversed) a carbon shell can be created using NH4OH solution to dissolve the silica. The formation of silica microparticles using silanol-functionalized polystyrene latexes proceeds along similar lines (Scheme 5.16) [77]. 

The pore size and distribution in the porous particles play essential roles in NPS synthesis. For example, only hollow capsules are obtained when MS spheres with only small mesopores (<3 nm) are used as the templates [69]. This suggests that the PE has difficulty infiltrating mesopores in this size range, and is primarily restricted to the surface of the spheres. The density and homogeneity of the pores in the sacrificial particles is also important to prepare intact NPSs. In a separate study, employing CaC03 microparticles with radial channel-like pore structures (surface area 8.8 m2 g 1) as sacrificial templates resulted in PE microcapsules that collapse when dried, which is in stark contrast to the free-standing NPSs described above [64]. 

The major strategies to enhance transmucosal peptide and other drug absorption include (a) coadministration with protease inhibitors, (b) the use of membrane permeation enhancers, (c) coadministration with a combination of absorption enhancers and protease inhibitors, (d) modification of peptide structure to improve metabolic stability or membrane permeation, and (e) use of nano- or microparticles [27], Some of these strategies have been investigated using the in situ rat model. 

We note that since Q involves the scattering coefficients, the radiation pressure force has resonance or near-resonance behavior. This first was observed and analyzed by Ashkin and Dziedzic (1977) in their study of microparticle levitation by radiation pressure. They made additional measurements (Ashkin and Dziedzic, 1981) of the laser power required to levitate a microdroplet, and Fig. 19 presents their data for a silicone droplet. The morphological resonance spectrum for the 180° backscattered light shows well-defined peaks at wavelengths corresponding to frequencies close to natural frequencies of the sphere. The laser power shows the same resonance structures in reverse, that is, when the scattered intensity is high the laser power required to levitate the droplet is low. 

Scanning electron microscopy (SEM) seems to have been used only scarcely for the characterization of solid lipid-based nanoparticles [104], This method, however, is routinely applied for the morphological investigation of solid hpid microparticles (e.g., to smdy their shape and surface structure also with respect to alterations in contact with release media) [24,38,39,41,42,80,105]. For investigation, the microparticles are usually dried, and their surface has to be coated with a conductive layer, commonly by sputtering with gold. Unlike TEM, in SEM the specimen is scanned point by point with the electron beam, and secondary electrons that are emitted by the sample surface on irradiation with the electron beam are detected. In this way, a three-dimensional impression of the structures in the sample, or of their surface, respectively, is obtained. 

Goschnick, J., J. Schuricht, and H. J. Ache, Depth-Structure of Airborne Microparticles Sampled Downwind from the City of Karlsruhe in the River Rhine Valley, Fresenius J. Anal. Chem.,... 

Solid state voltammetric methods can be used to obtain information on the composition of the materials used in works of art. Here, the methodology of the voltammetry of microparticles, developed by Scholz et al. [72, 73], will be presented. This methodology provides qualitative, quantitative, and structural information on sparingly soluble solid materials, as described in extensive reviews [74-77] and a precedent monograph [78], just requiring sample amounts in the ng-pg level. 

Fig. 1 A. shows the absorption and fluorescence spectra of 9AAHH in a PVA film. It can be seen that there exists an overlap between the two spectra. Fig. IB. shows the fluorescence spectra of 9AAHH doped single microparticles. Here the spectra contain ripple structures...

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