Double-emulsion solvent-evaporation technique

The encapsulation of bioactive agents, such as proteins or peptides, presents a special problem due to the delicacy of their structural conformation. Their biological activity may be irreversibly disturbed even by small changes of pH, temperature, or ionic concentration [192,200]. Spray-drying and double emulsion solvent evaporation techniques (w/o/w) have been suggested for the incorporation of proteins with retention of their bioactivity [99,192,202,198]. 

When formulating lipophilic materials, techniques often involve the use of organic solvents, interfaces with aqueous solutions, and high-shear forces [6], One of the most often used techniques to encapsulate proteins is the water/oil/water (w/o/w) double-emulsion solvent evaporation technique, in which an aqueous protein solution is emulsified into an organic solution of the matrix material. This primary emulsion is added to an outer aqueous phase in which particles start to harden as the organic solvent evaporates. Alternatively, the solid protein can be added directly to the organic solution in a solid/oil/water (s/o/w) emulsion method [23],... 

B. Double-emulsion-Solvent-evaporation Techniques for Preparation of Microspheres... 

It is known that the preparation of mierospheres by using 0/W emulsions is not an effieient method for die entrapment of water-soluble drugs as the eompounds rapidly dissolve in the aqueous eontinuous phase and are lost It has been widely aeeepted that the problem of inefficient eneapsulation of water-soluble dmgs ean be overcome by using the double-emulsion solvent-evaporation technique. Water-insoluble drugs are usually satisfactorily encapsulated by the 0/W emulsion teehnique (64, 65). 

The double-emulsion-solvent-evaporation technique is commonly used to prepare biodegradable hydro-phobic microspheres containing hydrophilic Pharmaceuticals, proteins, and polypeptides for sustained-release applications (66,70-78). In most cases the microspheres are in the range size 10-100 pm. However, recently, Blaneo-Prieto et al. (71) managed to reduce the microcapsule sizes to less than 5 pm. 

N. Zydowicz, E. Nzimba-Ganyanad, N. Zydowicz, PMMA microcapsules containing water-soluble dyes obtained by double emulsion/solvent evaporation technique, Polym. Bull. 2002, 47,457-463. 

E. Pindn-Segundo, M.G. Nava-Arzaluz, D. Lechuga-Ballesteros. Pharmaceutical polymeric nanoparticles prepared by the double emulsion-solvent evaporation technique. Recent Pat DrugDeliv Formul. 6 (3) 224-235,2012. 

An interesting investigation was made to indicate that PHB can form a new biodegradable adsorption material. Poly-3-hydroxybutyrate (PHB) was used as a new material to prepare a biomimetic adsorbent by a modified double emulsion solvent evaporation technique. The enrichment capacities of the adsorbent for toxic liposoluble organic compounds were evaluated by chlorobenzene (CB) and o-nitrochlorobenzene (u-NCB) with the adsorption isotherms, enrichment factor (EF) and enrichment kinetics. ... 

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