Microencapsulation by Coacervation

Tirkkonen et al. [38] developed an automatically controlled equipment for pilot processing of microcapsules formed by coacervation. It is possible to adjust the size of a batch of microcapsules manufactured by this equipment between 500 g and 5 kg [38]. 

The release of santosol oil from crosslinked PVA microcapsules prepared by coacervation, is shown to be mainly controlled by the crosslinking density of the PVA membrane and the size of the microcapsules [39]. As santosol oil used for encapsulation has very low solubiHty in water, release rate studies are carried out in water containing the surfactant SDS. It has been observed that, by increasing the 

Complex coacervation is similar to simple coacervation where another complimentary polyelectrolyte is used. Gelatin and gum arabic is a well-estabHshed system for microencapsulation by complex coacervation. Mayya et al. have reported a two-layer encapsulation of paraffin oil, based on a primary layer of interface active polyelectrolyte-surfactant complex, followed by a second layer of the conjugate polyelectrolyte-polyelectrolyte complex [41]. The procedure involves the dispersion of paraffin oil in 1% gelatin solution (pH adjusted to 6.5) containing SDS having concentration less than its CMC, followed by drop-wise addition of the solution of the other polyelectrolyte (1% gum arabic) into the dispersion. The pH is then ad- 

The commonly used complex coacervation processes of microencapsulation have several drawbacks, including a need for constant attention and the adjustment of stirring conditions, solution viscosity, pH, and temperature. The process also often produces significant amounts of agglomerated microcapsules. A European 

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Dobetti L, Pantaleo V. Hydrod5mamics in microencapsulation by coacervation. American Association of Pharmaceutical Scientists, Annual Meeting and Exposition, Indianapolis, IN, October 29-November 2, 2000. 

Nibant, N., Grandfils, C., Jerome, R., Teyssie, P., 1995. Microencapsulation by coacervation of poly(lactide-co-glycoUde) IV. Effect of the processing parameters on coacervation and encapsulation. Journal of Controlled Release 35, 117—125. 

Employing Polymer-Polymer Incompatibility FOR Oil Microencapsulation by Coacervation... 

Microencapsulation by coacervation is a common method for microcapsules production. It can be achieved by employing different methods, where the most common one is formation of an insoluble complex of two oppositely charged polymers and its subsequent deposition at surface of dispersed particles (e.g. emulsified oil droplets). In this way, microcapsules with coacervate shell are formed. Composition and microstructure of the coacervate shell are key to determine properties and application of microcapsules. 

In this chapter, novel method for microencapsulation by coacervation is presented. The method employs polymer-polymer incompatibility taking place in a ternary system composed of sodium carboxymethyl cellulose (NaCMC), hydroxypropylmethyl cellulose (HPMC), and sodium dodecylsulfate (SDS). In the ternary system, various interactions between HPMC-NaCMC, HPMC-SDS and NaCMC-(HPMC-SDS) take place. The interactions were investigated by carrying out detailed conductometric, tensiometric, turbidimetric, viscosimetric, and rheological study. The interactions may result in coacervate formation as a result of incompatibility between NaCMC molecules and HPMC/SDS complex, where the ternary system phase separates in HPMC/SDS complex rich coacervate and NaCMC rich equilibrium solution. By tuning the interactions in the ternary system coacervate of controlled rheological properties was obtained. Thus obtained coacervate was deposited at the surface of dispersed oil droplets in emulsion, and oil-content microcapsules with a coacervate shell of different properties were obtained. Formation mechanism and stability of the coacervate shell, as well as stability of emulsions depend on HPMC-NaCMC-SDS interaction. Emulsions stabilized with coacervate of different properties were spray dried and powder of microcapsules was obtained. Dispersion properties of microcapsules, and microencapsulation efficiency were investigated and found to depend on both properties of deposited coacervate and the encapsulated oil type. 

Qv, X. Y., Zeng, Z. P. Jiang, J. G. (2011). Preparation of lutein microencapsulation by complex coacervation method and its physicochemical properties and stability. Food Hydrocolloids, Vol. 25, 6, (August 2011), pp. (1596-1603), ISSN 0268-005X... 

Thomasin, C. Merkle, H.P. Gander, B. Physico-chemical parameters governing protein microencapsulation into biodegradable polyesters by coacervation. Int. J. Pharm. 1997, 147, 173-186. 

Pahnieri, G.F. Lauri, D. Martelli, S. Wehrle, P. Methoxy-butropate microencapsulation by gelatin-acacia complex coacervation. Drug Dev. Ind. Pharm. 1999, 25 (4), 399-407. 

Arneodo, C.J.F. Microencapsulation by complex coacervation at ambient temperature. FR 2732240 Al,... 

Siddiqui, O. and H. Taylor, Physical factors affecting microencapsulation by simple coacervation of gelatin. J. Pharm. Pharmacol., 35(2) (1983) 70-73. 

Martins, I. M. D. (2012). Microencapsulation of thyme oil by coacervation Production, characterization and release evaluation. PhD thesis. Faculdade de Engenharia da Universidade do Porto, Porto, Portugal. 

J. Korus, Microencapsulation of flavours in starch matrix by coacervation method, Polish Journal of Food and Nutrition Sciences, 10/51(1), 17-23 (2001). 

Coacervation n. The separation of a polymer solution into two or more liquid phases, one of which is a polymer-rich liquid. The term was introduced to distinguish this phenomenon from the precipitation of a polymer solute in solid form. The process is used in microencapsulation by emulsifying or dispersing the material to be encapsulated with a solution of the polymer. By changing the temperature or concentration of the mixture, or by adding another polymer or solvent, a phase separation may be induced and the polymeric portion forms a thin coating on the external surfaces of the particles. After further treatment to solidify the polymeric wall, the capsules can be isolated in powder form by filtration. It is an intermediate stage between sol and gel formation. 

Korus, J., Microencapsulation of flavors in starch matrix by coacervation method, Polish J. FoodNutr. Sci., 10, 1, p. 17, 2001. 

Phase separation microencapsulation procedures are suitable for entrapping water-soluble agents in lactide/glycolide excipients. Generally, the phase separation process involves coacervation of the polymer from an organic solvent by addition of a nonsolvent such as silicone oil. This process has proven useful for microencapsulation of water-soluble peptides and macromolecules (48). 

Several other investigators have reported microencapsulation methods based upon polyelectrolyte complexes [289, 343]. For example, oppositely-charged polyelectrolytes (Amberlite IR120-P (cationic) and Amberlite IR-400 (anionic)) were recently used along with acacia and albumin to form complex coacervates for controlled release microcapsule formations [343]. Tsai and Levy [344,345] produced submicron microcapsules by interfacial crosslinking of aqueous polyethylene imine) and an organic solution of poly(2,6 dimethyl... 

Xing, F., Cheng, G., Yang, B., Ma, F. (2004). Microencapsulation of capsaicin by the complex coacervation of gelatin, acacia and tannins. Journal of Applied Polymer Science, 91,2669-2675. 

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