Microparticles, polymeric polymerization methods

Kriwet, B. Walter, E. Kissel, T. Synthesis of bioadhesive polyfacrylic acid) nano- and microparticles using an inverse emulsion polymerization method for the entrapment of hydrophilic drug candidates. J. Control. Release 1998, 56 (1-3), 149-158. 

The distribution of Ab can also enhance the antigen-binding efficiency of the immunosorbent [24]. Microencapsulation of Abs inside polymeric microparticles is a method that provides high adsorption capacity and stability of... 

Spherical microparticles are more difficult to manufacture and can be prepared by several methods. One method prepares silica hydrogel beads by emulsification of a silica sol in an immiscible organic liquid [20,21,24,25]. To promote gelling a silica hydrosol, prepared as before, is dispersed into small droplets in a iater immiscible liquid and the temperature, pH, and/or electrolyte concentration adjusted to promote solidification. Over time the liquid droplets become increasingly viscous and solidify as a coherent assembly of particles in bead form. The hydrogel beads are then dehydrated to porous, spherical, silica beads. An alternative approach is based on the agglutination of a silica sol by coacervation [25-27], Urea and formaldehyde are polymerized at low pH in the presence of colloidal silica. Coacervatec liquid... 

The water-in-oil-in-water (w/o/w) emulsion method (Figure 11.4) is the predominant method used for encapsulation of biomacromolecules in these microparticles. Protein solution forms the internal water phase of the w/o/w emulsion. Loading efficiency of the microparticles has not been optimal using water or buffer as an internal phase, so water is sometimes substituted with polymeric liquids, such as low molecular weight polyethylene glycol. The primary emulsion is then added to a secondary liquid phase, forming the secondary emulsion. The solvent for the... 

Methods of preparing polymeric microparticles with tailored surface chemistries are of technological importance in a wide range of applications including drug delivery, biochemical diagnostics, and paint/coating products [34], Microparticle... 

Closely related to the polymeric surfactant stabilization of microparticle surfaces is the stabilization of surfaces by the segregation of one component of a blend. This powerful method of surface engineering involves the inherent thermodynamically driven enrichment of surfaces by the blend component possessing the lowest surface energy. 

The microparticle system has become an indispensable part of the controlled drug delivery fields for the past few decades since it can readily be adapted for various administration methods. In particular, biodegradable polymeric microparticles can provide a number of advantages over conventional parenteral formulations ... 

A technique based on the formation of a multiple emulsion with an external aqueous phase was developed for the encapsulation of water-soluble drugs in order to replace the external oil phase. Possible unwanted interactions between the oil and the emulsified wax such as swelling or dissolution of the wax, clean-up requirements of the final product, and recovery of the oil phase could be eliminated. In analogy to the encapsulation of water-soluble drugs within polymeric microparticles by a w/o/w-solvent evaporation method, a molten wax phase was used instead of an organic polmer solution. A heated aqueous solution of pseudoephedrine HCl was emulsified into the molten carnauba wax, followed by the emulsification of this w/o-emulsion into a heated external aqueous phase. The temperature of the internal and external aqueous phases had to be kept above the melting temperature of the wax in order to avoid premature... 

The combination of experimental evidence and computational modeling show conclusively that stable, homogeneously blended (bulk-immiscible) mixed-polymer composites can be formed in a single microparticle of variable size. To our knowledge, this represents a new method for suppressing phase-separation in polymer-blend systems without compatibilizers that allows formation of polymer composite micro- and nanoparticles with tunable properties such as dielectric constant. Conditions of rapid solvent evaporation (e.g. small (<10 pm) droplets or high vapor pressure solvents) and low polymer mobility must be satisfied in order to form homogeneous particles. While this work was obviously focused on polymeric systems, it should be pointed out that the... 

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