Polymers microencapsulation

Hydrogels and amphiphilic membranes Poly(carbophosphazenes) and poly(thiophosphazenes) New condensation syntheses NLO and high refractive index polymers Microencapsulation of mammalian cells (PCPP) Polyphosphazene polymer blends and IPN s Borazine derivatives Poly(phosphazophosphazenes)... 

Morris, W. Steinhoff, M.C. Russell, P.K. Potential of polymer microencapsulation technology for vaccine innovation. Vaccine 1994, 12, 5-11. 

Polymer-microencapsulated scandium and osmium catalysts have recently been developed by Kobayashi and coworkers [ 119-121]. This protocol has been... 

Ghosh SK (ed) (2006) Functional coatings by polymer microencapsulation. Wiley, New York Goodman WA (Ed) (2005) Optical materials and structures technologies II 1-2 August 2005, San Diego, California, USA. SPIE - The International Society for Optical Engineering... 

Scandium(III) trifluoromethanesulfonate (Sc(OTf)3) is extensively used in organic synthesis to catalyze a wide variety of carbon-carbon bond-forming reactions in aqueous media. The polymer microencapsulated triflate ME catalysts are recoverable and reusable, often reduce metal leaching, and have activity similar to that of their homogeneous counterparts [128]. 

E. Bourgeat-Lami and E. Duguet, in Eunctional Coatings by Polymer Microencapsulation, ed. S. K. Ghosh, Wiley-VCH, Weinheim, 2006, p. 85. 

Coa.cerva.tlon, A phenomenon associated with coUoids wherein dispersed particles separate from solution to form a second Hquid phase is termed coacervation. Gelatin solutions form coacervates with the addition of salt such as sodium sulfate [7757-82-6] especially at pH below the isoionic point. In addition, gelatin solutions coacervate with solutions of oppositely charged polymers or macromolecules such as acacia. This property is useful for microencapsulation and photographic apphcations (56—61). 

Several parenteral microencapsulated products have been commercialized the cote materials ate polypeptides with hormonal activity. Poly(lactide— glycohde) copolymers ate the sheU materials used. The capsules ate produced by solvent evaporation, polymer-polymer phase separation, or spray-dry encapsulation processes. They release their cote material over a 30 day period in vivo, although not at a constant rate. 

It is sometimes possible to add properties in Hquid formulations that provide additional functions. Examples in development or in commercial use as of 1993 include microencapsulation (qv) of enzymes for protection against bleach when dispersed in a Hquid detergent addition of certain polymers to protect the enzyme after it has been added to Hquid detergents (32), or to boost activity in the final appHcation addition of surfactants or wetting agents. 

With the development of the polymer field in medicine, great attention has been paid to particulate forms of drugs [82], The most widespread methods for the preparation of particulate drugs are microencapsulation and microgranulation, i.e., the inclusion of BAS into spherical shapes of predetermined dimensions. One form of particulate drugs is microcapsules or artificial cells as they were called by... 

Microspheres and microcapsules of lactide/glycolide polymers have received the most attention in recent years. Generally, three microencapsulation methods have been employed to afford controlled release formulations suitable for parenteral injection (1) solvent evaporation, (2) phase separation, and (3) fluidized bed coating. Each of these processes requires lactide/glycolide polymer soluble in an organic solvent. 

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). 

There are literally dozens of patents and literature references addressing the microencapsulation of bioactive agents in polymers. 

Aseptic processing is particularly useful with microencapsulated products, which almost always involve solutions of the polymer in organic solvents. Occasionally, bioactive molecules sensitive to... 

The steroid-loaded formulations are prepared by a patented solvent evaporation process (45,46). Basically, the wall-forming polymer and the steix>id are added to a volatile, water-immiscible solvent. The dispersion or solution is added to an aqueous solution to form an oil-in-water emulsion. The volatile solvent is then removed to afford solid microparticles. The microparticles are usually subd vided with sieves to isolate fractions of the desired diameters. It is i nper-ative that a reliable and reproducible microencapsulation procedure be used to fabricate long-acting formulations. 

The steroid microsphere systems are probably the most successful drug delivery formulations thus far ba.sed on lactide/glycolide polymers. Several of these products appear to be on track for human and animal applications in the 1990s. The success of these formulations is due to the known safety of the polymer, the reproducibility of the microencapsulation process, reliability in the treatment procedure, and in vivo drug release performance (80). 

A human contraceptive vaccine based on lactide polymers is currently being developed. The antigen is a 37-amino-acid peptide of B-HCG conjugated to diphtheria toxoid. The antigen is administered wtih microencapsulated muramyl dipeptide as an adjuvant. Studies in rabbits have shown 9-12 months of elevated antibody liter following... 

Microencapsulation with PCL using the solvent evaporation method can be experimentally difficult. For example, PCL was the only polymer of five that failed to yield spherically shaped microcapsules using this technique (82). The insecticide Abate has been incorporated into PCL (21% loading) by the solvent separation method in a comparative study, PCL afforded good-quality microspheres although poly (methyl methacrylate) microcapsules were smoother and had fewer defects (83). 

Chloropromazine (8—34 wt% loading) has been microencapsulated in PCL-cellulose propionate blends by the emulsion solvent evaporation method (61). Phase separation for some ratios of the two polymers was detectable by SEM. The release rate from microcapsules in the size range of 180-250 pm in vitro (Fig. 11) was directly proportional to the PCL content of the blend, the half-life (50% drug release)... 

The second general method, IMPR, for the preparation of polymer supported metal catalysts is much less popular. In spite of this, microencapsulation of palladium in a polyurea matrix, generated by interfacial polymerization of isocyanate oligomers in the presence of palladium acetate [128], proved to be very effective in the production of the EnCat catalysts (Scheme 3). In this case, the formation of the polymer matrix implies only hydrolysis-condensation processes, and is therefore much more compatible with the presence of a transition metal compound. That is why palladium(II) survives the microencapsulation reaction... 

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