Aqueous solutions, microparticles

The steroid-loaded formulations are prepared by a patented solvent evaporation process (45,46). Basically, the wall-forming polymer and the steix>id are added to a volatile, water-immiscible solvent. The dispersion or solution is added to an aqueous solution to form an oil-in-water emulsion. The volatile solvent is then removed to afford solid microparticles. The microparticles are usually subd vided with sieves to isolate fractions of the desired diameters. It is i nper-ative that a reliable and reproducible microencapsulation procedure be used to fabricate long-acting formulations. 

Crosslinked polyacrylamide latexes encapsulating microparticles of silica and alumina have also been prepared by this method [179], Three steps are involved a) formation of a stable colloidal dispersion of the inorganic particles in an aqueous solution containing acrylamide, crosslinker, dispersant, and initiator b) HIPE preparation with this aqueous solution as the dispersed phase and c) polymerisation. The latex particles are polyhedral in shape, shown clearly by excellent scanning electron micrographs, and have sizes of between 1 and 5 pm. 

Chitosan is a polymer produced from hydrolysis of natural chitin. Chitosan is not readily soluble in aqueous solutions, but can be solubilized and is thus considered with other water soluble polymers. In the hydrophobic form, chitosan has been treated in a similar manner to other hydrophobic polymers with microparticles produced by emulsion and phase separation techniques. Microparticles can be taken up by the gastrointestinal lining in a manner similar to that discussed for other hydrophobic microparticles. 

Moreover, the use of MIP microparticles with quantum dots (QDs) as signal transducers for the detection of nitroaromatic explosives has been very recently presented [71]. LOD for aqueous solutions was 30.1 pM and 40.7 pM for DNT and TNT, respectively. Although the LODs of the presented system are 100 times lower than those for other already developed TNT sensitive systems, this example presents a new interesting approach in the MIPs technology. If the colloidal stability and size distribution of the microparticles were improved, this example would present a reasonable approach to MIP chemosensor preparation. 

Paraffin impregnated graphite electrode (PIGE) - electrode prepared from graphite rods by impregnation with melted paraffin under vacuum. These electrodes are not permeated by aqueous solutions and can be used for solution studies, as well as for immobilizing microparticles and microdroplets to study their electrochemistry. See also - carbon, - voltammetry of immobilized microparticles. 

Sarkari, M. Darrat, I. Knuston, B. CO2 and fluorinated solvent-based technologies for protein microparticle precipitation from aqueous solutions. Biotechnol. Prog. 2003, iP, 448-454. 

A technique based on the formation of a multiple emulsion with an external aqueous phase was developed for the encapsulation of water-soluble drugs in order to replace the external oil phase. Possible unwanted interactions between the oil and the emulsified wax such as swelling or dissolution of the wax, clean-up requirements of the final product, and recovery of the oil phase could be eliminated. In analogy to the encapsulation of water-soluble drugs within polymeric microparticles by a w/o/w-solvent evaporation method, a molten wax phase was used instead of an organic polmer solution. A heated aqueous solution of pseudoephedrine HCl was emulsified into the molten carnauba wax, followed by the emulsification of this w/o-emulsion into a heated external aqueous phase. The temperature of the internal and external aqueous phases had to be kept above the melting temperature of the wax in order to avoid premature... 

Glassy carbon felt electrodes modified by electrodeposited poly(pyrrole-viologen) films containing electroprecipitated microparticles of precious metals like Pt, Pd, Rh or Ru have been shown to be suitable for the electrocatalytical hydrogenation of several organic substrates including benzonitrile, in acidic aqueous solution. Pd exhibited the highest current efficiency and yields for benzylamine formation when compared with Pt and Rh. 

Gel microparticles are formed from the concept of gelation as an encapsulation technology. Gelation is based on the formation of a solution, dispersion, or the emulsification of the core material in an aqueous solution containing a hydrophilic polymer (hydrocolloid) capable of forming a gel under an external action, either physical or chemical. 

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