Solvents displacement method

Ribeiro, H.S., Chu, B.S., Ichikawa, S., Nakajima, M. (2008). Preparation of nanodispersions containing P-carotene by solvent displacement method. Food Hydrocolloids, 22, 12-17. 

Swollen starch was prepared by heating a 15% aqueous dispersion with aata-tion for 1 hour at 65° C. Excess water was removed by filtration. The gelatinized starch was prepared in a like manner at 85° C. Where the inclusion method of adding the monomer was used, it was incorporated by the solvent displacement method originated by Hermans and De Leeuw (3). The water in the gelatinized starch was displaced with methanol and the methanol displaced with the monomer to be used. 

Scheme 3 A summary of the solvent-displacement method by which the particles in Figure 7 were prepared. See, for example, Ref. 71.

Figure 7 Ciclosporin A nanoparticles number average diameter 200 nm, prepared by a solvent displacement method (see Scheme 3). Source. From Ref. 72.

If the copolymer is water soluble, the easiest method for generating polymersomes is direct dissolution of the dry polymer in aqueous media. However, this method cannot be used for insoluble water amphiphilic block-copolymers, for which a solvent-free or a solvent displacement method must be used. With the solvent-free method, a homogeneous amphiphilic polymer film is first deposited on a solid surface, and then subsequently hydrated in an aqueous buffer solution to form supramolecular assemblies upon desorption from the support. This is the method of choice when working under organic solvent-free conditions is mandatory, as for example for the combination with biomolecules. " When applying the solvent displacement method, the copolymer is first dissolved in an appropriate solvent, and then slowly mixed with water the reduced solubility of the copolymer drives the self-assembly process and formation of supramolecular assemblies, such as polymersomes. The organic solvent is eventually extracted, but complete removal of solvent traces is not possible and traces of organic solvents could affect sensitive biomolecules. 

Whilst the solvent-free and solvent-displacement methods yield polymersomes with diameters ranging from nanometers up to a few micrometers, giant vesicles of tens of micrometers in diameter can be formed by electroformation or copolymer stabilized double emulsions methods. Electroformation of giant vesicles is triggered by an a.c. field that is applied across an amphiphilic polymer film to enhance water diffusion and film hydration. The double emulsion method consists on the formation of a leaflet of the inner membrane using one copolymer type as a stabilizer for a... 

C) the solvent displacement method, and (D) the double emulsion method for giant unilamellar vesicles. 

Nanocapsules act like a reservoir, which are called vesicular systems. They carry the active substance entrapped in the solid polymeric membrane or on their surfaces. The cavily inside contains either oil or water. A schematic diagram of Polymer Nanocapsules is shown in Fig. 9.2 [5], There are different methods that are used nowadays to prepare polymeric nanoparticles, such as nanoprecipitation (also termed as the solvent diffusion and solvent displacement method), solvent evaporation, dialysis, microemulsion, surfactant-free emulsion, salling-out, supercritical fluid technology, and interfacial polymerization [2]. Among these methods, nanoprecipitation is a fast and simple process, which does not require a pre-prepared polymer emulsion before the nanoparticle preparation. It produces a dispersion of nanoparticles by precipitation of preformed hydrophobic polymer solution. Under... 

F. 9.17 Solvent displacement method of nanoparticle formation based on the interfacial disturbances [7]... 

---