Microspheres emulsions

Various coUoidal systems formed with block or graft copolymers, such as liposomes, microspheres, emulsions have been described for oral drug-delivery systems. Block and graft copolymers in their micellar form or as steric stabilizers for colloidal particles are well suited for oral and injectable drug formulations and diagnostic systems if they meet the requirement of biocompatibility and preferably of biodegradability [278,279]. 

Water-in-od emulsion explosives have been made as typified by a formulation containing 20% water, 12% oil, 2% microspheres, 1% emulsifier, and 65% ammonium nitrate. The micro droplets of an emulsion explosive offer the advantage of intimate contact between fuel and oxidizer, and tend to equal or outperform conventional water-based slurries. 

Soapless seeded emulsion copolymerization has been proposed as an alternative method for the preparation of uniform copolymer microspheres in the submicron-size range [115-117]. In this process, a small part of the total monomer-comonomer mixture is added into the water phase to start the copolymerization with a lower monomer phase-water ratio relative to the conventional direct process to prevent the coagulation and monodispersity defects. The functional comonomer concentration in the monomer-comonomer mixture is also kept below 10% (by mole). The water phase including the initiator is kept at the polymerization temperature during and after the addition of initial monomer mixture. The nucleation takes place by the precipitation of copolymer macromolecules, and initially formed copolymer nuclei collide and form larger particles. After particle formation with the initial lower organic phase-water ratio, an oligomer initiated in the continuous phase is... 

The soapless seeded emulsion copolymerization method was used for producing uniform microspheres prepared by the copolymerization of styrene with polar, functional monomers [115-117]. In this series, polysty-rene-polymethacrylic acid (PS/PMAAc), poly sty rene-polymethylmethacrylate-polymethacrylic acid (PS/ PMMA/PMAAc), polystyrene-polyhydroxyethylmeth-acrylate (PS/PHEMA), and polystyrene-polyacrylic acid (PS/PAAc) uniform copolymer microspheres were synthesized by applying a multistage soapless emulsion polymerization process. The composition and the average size of the uniform copolymer latices prepared by multistage soapless emulsion copolymerization are given in Table 11. 

The uniform polymeric microspheres in submicron-or micron-size range can also be prepared as seed particles by the soapless emulsion or dispersion polymerization of a hydrophobic monomer like styrene. The uniform seed particles are swollen with the organic phase including functional comonomer, monomer, and oil-soluble initiator at a low temperature in an aqueous... 

A solid emulsion is a suspension of a liquid or solid phase in a solid. For example, opals are solid emulsions formed when partly hydrated silica fills the interstices between close-packed microspheres of silica aggregates. Gelatin desserts are a type of solid emulsion called a gel, which is soft but holds its shape. Photographic emulsions are gels that also contain solid colloidal particles of light-sensitive materials such as silver bromide. Many liquid crystalline arrays can be considered colloids. Cell membranes form a two-dimensional colloidal structure (Fig. 8.44). 

The emulsion technique is convenient when the drug is particularly sensitive to certain parameters connected to the spray-drying. The emulsion technique may be associated to cross-Unking or other treatments of the microspheres. The following examples are self-explanatory. 

Microspheres were prepared from carboxymethyl chitosan and alginate by emulsion phase separation. The encapsulated bovine serum albumin was... 

The preparation of microspheres can be accomplished by either of two methods thermal denaturation, in which the microspheres are heated to between 95 and 170°C, and chemical crosslinking with glutaraldehyde in a water-in-oil emulsion. Well-defined microspheres can be easily prepared using these methods in large batches which are usually physically and chemically stable. Newer preparation methods for the preparation of albumin microspheres have been described by several authors (84-88). 

Juliano, R. L. (1988). Factors effecting the clearance kinetics and tissue distribution of liposomes, microspheres and emulsions,... 

Core-shell nanocomposite of Mg(OH)2/PMMA with an average particle size of ca. 500nm where Mg(OH)2 is the core and PMMA is the shell was successfidly prepared by the emulsion polymerization of MMA in the presence of surface modified Mj OH)2. The grapelike ( re-shell microspheres with PMMA nodules could he obtained as stable latex. 

An excellent carrier is needed to deliver a sufficient amount of prostaglandins to the diseased site. Liposomes have been studied for a long time as possible drug carriers. However, the clinical use of liposomes has delayed because of some difficulties in mass production, sterilization, stability and safety. Since 1980 we have attempted to use lipid microspheres (lipid emulsions) instead of liposomes as a better carrier for lipophilic drugs (7). 

It was found in animal and clinical studies that lipid microspheres accumulated particularly in arteriosclerotic and damaged vessel walls. Earlier studies (16,17) of lipid emulsions demonstrated also that lipid microspheres had an affinity to vascular walls, including capillaries, like chylomicrons. Shaw et al. reported that they had... 

P Couvreur, MJ Blanco-Prieto, F Puisieux, B Roques, E Fattal. Multiple emulsion technology for the design of microspheres containing peptides and olegopep-tides. Adv Drug Del Rev 28 85-96, 1997. 

Intralymphatic delivery (lymphotropic), as microspheres-in-oil emulsion for delivery of cytostatics 5-Fluorouracil... 

Fig. 10 Release of cromolyn sodium (sodium cromoglycate) from human serum albumin microspheres prepared using a water-oil emulsion technique with 5% glutaraldehyde as cross-linking agent. Dissolution medium pH 7 phosphate buffer. (From Ref. 98.)... 

Foamed cement slurries have been used to provide a low density cement slurry to reduce permeability damage to highly sensitive formations through reduced fluid loss (29). Glass microspheres have also been used to substantially reduce cement slurry density (30, 31). Other additives which reduce cement slurry density to a lesser extent include bentonite, fly ash, silicates, perlite, gilsonite, diatomaceous earth, and oil emulsions (see citations in reference 29). 

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