Coacervation technique

Xylan-based micro- and nanoparticles have been produced by simple coacervation (Garcia et al., 2001). In the study, sodium hydroxide and chloride acid or acetic acid were used as solvent and non-solvent, respectively. Also, xylan and surfactant concentrations and the molar ratio between sodium hydroxide and chloride acid were observed as parameters for the formation of micro- and nanoparticles by the simple coacervation technique (Garcia et al., 2001). Different xylan concentrations allowed the formation of micro- and nanoparticles. More precisely, microparticles were found for higher concentrations of xylan while nanopartides were produced for lower concentrations of the polymer solution. When the molar ratio between sodium hydroxide and chloride acid was greater than 1 1, the partides settled more rapidly at pH=7.0. Regarding the surfactant variations, an optimal concentration was found however, at higher ones a supernatant layer was observed after 30 days (Garda et al., 2001). 

Nasa SL, Yadav S. Microencapsulation of metoprolol tartrate using phase separation coacervation techniques. East Pharm 1989 32 133-134. 

Saihi, D., Vroman, I., Giraud, S., and Bourbigot, S. 2005. Microencapsulation of ammonium phosphate with a polyurethane shell—Part I Coacervation technique. React. Funct. Polym. 64 127-138. 

In summary, the feasibility of coacervation has been shown on industrial scale, although it is probably fair to say that this technology is only scarcely used in pharmaceutical industry. Primarily for its physicochemical complexity and limitations with respect to residuals or processing components, efforts have been made to replace the coacervation technique by simpler technologies. To what extend new applications of coacervation technologyin pharmaceutical industry will be successfully commercialized will largely depend on the market needs and patient benefits of these new... 

Bayomi MA, al-Suwayeh SA, el-Helw AM, Mesnad AF. Preparation of casein-chitosan microspheres containing diltiazem hydrochloride by an aqueous coacervation technique. Pharma Acta Helv 1998 73 187-192. 

Two main coacervation techniques can be considered aqueous, which can only be used to encapsulate water-insoluble materials (hydrophobic core materials presented in solid or liquid state), and organic in which the organic phase permits the encapsulation of hydro-soluble material, requiring the utilization of organic solvents (Martins, 2012). 

Similarly, in the solid in oil in oil (s/o/o) double emulsions, the internal solid phase and external oil phase are separated by an oil phase. The s/o/o emulsion can be prepared by dispersing solid particles in an organic solvent, for example, methylene chloride, and then mixed with a polymer solution. Alternatively, the dispersion of solids in organic solvent can be coated with a suitable polymer using a coacervation technique. 

Chitosan was shown to be a biocompatible [132] and biodegradable cationic polyelectrolyte that could be used to prepare capsules for pharmaceutical and biomedical fields [133,134]. The capsules can be prepared in different ways. The first method is the coacervation technique, where a solution of chitosan is blown into a nonsolvent and the polymer precipitates at the surface of the droplets, thereby forming capsules [135]. The second method is the coating process [136], where the oil phase containing the product is blown into the chitosan solution, causing the polymer to precipitate at the surface of the droplets. The surface properties of chitosan were used to produce capsules by crossHnking chitosan at the interface [137-139], but the formed capsules were often quite large (from 500 run to several micrometers) and the size distribution was wide. 

Dubin and Park [13] have utilized selective complexation of poly(l-alkyl-4-vinylpyridiniums) with mixtures of proteins to develop a convenient new method for isolation of proteins of interest. For example, they were able to cleanly separate bovine serum albumin (BSA) from ribonuclease (RNase) by a selective coacervation technique. The net negatively charged BSA forms a strong ionic complex with 2 and precipitates to leave only the RNase in solution. 

Ma J, Feng P, Ye C, Wang Y, Fan Y (2001) An improved interfacial coacervation technique to fabricate biodegradable nanocapsules of an aqueous peptide solution from polylactide and its block copolymers with poly (ethylene glycol). Colloid Polym Sci 279(4) 387-392... 

Shanmuganathan et al. improved this method [18]. Chitosan microspheres (CSM) were prepared by the W/0 emulsification process along with an ionic coacervation technique. The KOH solution in / -octanol was added into the w/o emulsion of chitosan drop by drop. Then the ionic gelation was initiated. After the reaction, the chitosan microspheres were removed and rinsed in demineralized water baths. The whole process was carried out at room temperature. 

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