Solvent removal microencapsulation

A variety of methods have been reported for producing microspheres including phase separation by polymer/polymer incompatibility and coacerva-tion [81] solvent evaporation or solvent removal [82] hot-melt microencapsulation spray drying interfacial polymerization and supercritical fluidprocessing teehniques (such as the gas antisolvent spray precipitation process [83] or rapid expansion of supercritical fluids [84]). The characteristics of the most important of these methods have been reviewed [85, 86]. 

Mathiowitz E, Saltzman M, Domb A. Polyanhydride microspheres as drug carriers. II Microencapsulation by solvent removal. J Appl Polym Sci 1988 35 755-774. 

Microencapsulation processes based on tlie solvent removal method have been reviewed in few book chapters and review articles "-" however, the current chapter presents classical expertize and essential old results, in addition to an up-to-date findings pertaining to this method, and the potential use of produced microparticles in the delivery of drugs to human. 

Obeidat WM. Recent patents review in microencapsulation of pharmaceuticals using the emulsion solvent removal methods. Recent Patents on Drug Delivery and Formulation. November 2009 3(3) 178-192. PubMed PMID 19925442. 

Bogataj M, Mrhar A, Kristi A, KozjekF. EudragitEmicrospheres containing bacampicillin Preparation by solvent removal methods. Journal of Microencapsulation. July-September 1991 8(3) 401-406. PubMed PMID 1941447. 

Generally, a continuous phase that is a nonsolvent for the microencapsulated bioactive compound is favorable. For lipophilic compounds, aqueous solutions may be comfortably chosen while the use of hydrophobic, organic liquids is preferred as coutinuous phase for the encapsulation of hydrophilic compounds. The ideal rate of solvent removal depends on a variety of factors like the type of matrix material, drug and solvent as weU as the desired release profile of the microspheres. 

Mathiowitz, E., Saltzman, W., Domb, A., Dor, P., Langer, R., 1988. Polyanhydride micro-spheres as drug carriers. II. Microencapsulation by solvent removal. Journal of Applied Polymer Science 35, 755—774. 

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. 

Spray drying. Microencapsulation by spray drying is an ideal method for poorly water-soluble drugs. The drug is dispersed in polymer (coating) solution, and then this dispersion is atomized into an airstream. The air, usually heated, supplies the latent heat of vaporization required to remove the solvent and forms the microencapsulated product. This technique is employed most commonly when microcapsules are intended for oral use because the resulting microspheres are porous in nature, and large batch sizes are required.89... 

Methods of coacervation, physical adsorption, precipitation by a nonsolvent or solvent evaporation are used for microencapsulation. A developed surface may be prepared by removing solvent from a vitrified polymer by sublimation at low temperature under vacuum. 

For microencapsulation of inorganic nanoparticles, preparation methods like in situ polymerization may be used [102]. However, these methods often require toxic organic solvents and surfactants. Furthermore, the removal of residual surfactants or solvents is needed, since they cause faults in the product An environmentally benign solvent like supercritical carbon dioxide can be used to encapsulate inorganic nanoparticles. But its use is limited because of the low... 

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