Formulations microencapsulated

Carotenoid-containing granular Emulsification and formulation microencapsulation... 

By virtue of their unique formulation, microencapsulated pesticides have significantly lower dermal and oral toxiclties than the corresponding emulslflable concentrate formulations. Microencapsulated methyl parathion (MMP) was Introduced commercially in 1974 In 1976 and thereafter reports of bee kills allegedly caused by this product were published, primarily In the news media and non-refereed journals. Claims were subsequently made that MMP Is carried back to the hive and Is uniquely hazardous because the size of the microcapsules Is In the range of many pollens. 

Although expensive, pre-applied threadlockers avoid the necessity of handling liquid anaerobics on a production line. Attempts have been made to formulate microencapsulated systems that would be truly pre-applied adhesives for face-face bonding, but the necessity of thoroughly mixing the monomers and catalysts has never been successfully overcome (except in the case of threaded fasteners). 

Slow release formulations incorporate nonpersistent compounds, eg, methyl parathion, insect growth regulators, and sex pheromones, in a variety of granular, laminated, microencapsulated, and hoUow-ftber preparations. 

The number of microencapsulated commercial oral formulations available and the volume of these formulations sold annuaUy is comparatively smaU. This may reflect the difficulty of developing new dmg formulations and bringing them successfully to market or the fact that existing microencapsulation techniques have had difficulty economically producing mictocapsules that meet the strict performance requirements of the pharmaceutical industry. One appHcation that is a particularly active area of development is mictocapsules or microspheres for oral deUvery of vaccines (45,46). 

Microencapsulation has much hidden potential for the food industry which promises to be tapped in the future (62). An interesting discussion of the problems that have been encountered while attempting to develop microcapsule formulations for commercial use in food products has been presented (65) and a review provides a number of references to food encapsulation studies (66). 

The encapsulation of herbicides has received much attention. Encapsulated alachlor is a high volume herbicide product generally sold as a Hquid formulation, although a dry granule version is also available. The capsules, produced by interfacial polymeri2ation (11), are reported to be spherical with a diameter of 2—15 p.m (75). Two thiocarbamate herbicides, EPTC and vemolate [1929-77-7], were encapsulated by interfacial polymeri2ation because they are volatile compounds. When appHed in unencapsulated form, they must be incorporated in the soil within two hours in order to provide effective weed control. When appHed as a microencapsulated formulation, the rate of volatili2ation is lower and soil incorporation can be delayed 24 hours (76). 

Another important apphcation for 4-/ f2 -octylphenol is ia the production of phenoHc resias. Novolak resias based oa 4-/ f2 -octylpheaol are widely used ia the tire iadustry as tackifiers. The tackiaess of these resias biads the many parts of an automobile tire prior to final vulcanization. A specialty use for novolak resias based oa 4-/ f2 -octylpheaol is the productioa of a ziacated resia, which is formulated as a dispersioa ia water and coated onto paper ia combination with eacapsulated leuco dyes to yield carbonless copy paper (see Microencapsulation). Pressure from writing bursts the encapsulated leuco dye, which is converted from its colorless form to its colored form by the ncated resin (53). Novolak resias based oa 4-/ f2 -octylpheaol are also used ia the productioa of specialty printing inks. 

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. 

Microencapsulation is usually attempted because a proposed ingredient is too reactive or too sensitive to withstand exposure to other ingredients nr tQ the environment. For example, the very energetic oxidizer nitronium perchlorate (NP) cannot be mixed directly into a proplnt or expl formulation because of its extreme reactivity. It is actually a solid anhydride between nitric and perchloric acids, and even traces of moisture hydrolyze the surface layers to free coned nitric... 

Palmer JS. 1978. Toxicologic evaluation of a microencapsulated formulation of methyl parathion applied dermally to cattle. Am J Vet Res 39 429-431. 

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. 

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). 

Fig. 10). A phase separation microencapsulation technique was used to formulate nafarelin acetate in 50 50, 69 31, and 45 55 DL-lactide/glycolide copolymers (120). 

Encapsulated scale inhibitors have been developed. This type of scale inhibitor allows chemical release over an extended period [865,1452], Microencapsulated formulations may contain a gelatin coating with a multipurpose cocktail, such as [1006,1007] ... 

J. L. Cleland and A. J. Jones, Stable formulations of recombinant human growth hormone and interferon-y for microencapsulation in biodegradable microspheres, Phar. Res, 13(10), 1464 (1996). 

Nayak B, Panda AK, Ray P et al (2009) Formulation, characterization and evaluation of rotavirus encapsulated PLA and PLGA particles for oral vaccination. J Microencapsul 26 154-165... 

Formulations of chlorpyrifos include emulsifiable concentrates, wettable powders, granules, pellets, microencapsulates, and impregnated materials. Suggested diluents for concentrates include water and petroleum distillates, such as kerosene and diesel oil. Carrier compounds include synthetic clays with alkyl/aryl sulfonates as wetting agents (Table 14.1). Little information is available to assess the influence of various use formulations on toxicity, dispersal, decomposition, and bioavailability. Chemical and other properties of chlorpyrifos are summarized in Table 14.2 and Figure 14.1. 

Sol-gel microencapsulation in silica particles shares the versatility of the sol-gel molecular encapsulation process, with further unique advantages. Sol-gel controlled release formulations are often more stable, potent and tolerable than currently available formulations. The benefits of microencapsulation can be customized to deliver the maximum set of benefits for each active ingredient. Overall, these new and stable combinations of active pharmaceutical ingredients (APIs) result in improved efficacy and usability. 

Photodegradation. Schaefer and Dupras (39) reported that emulsifiable formulations of methoprene at 0.1 ppm in water showed a rapid photodissipation in sunlight, whereas the commercial, microencapsulated formulation remained biologically active in water for several days under similar conditions. Aqueous solutions of methoprene undergo very rapid (t, <1 hr) photoequilibration to a mixture (,ui l) of 2E, 4E 2Z, 4E isomers (26, 39). 

Wakerly, Z., Fell, J.T., Attwood, D., and Parkins, D., Peetin/ethyl eellulose film-eoating formulations for colonic drug delivery, Pharm. Res., 13 1210-1212 (1996). Lorenzo-Lamosa, M.L., Remunan-Lopez, C., Vila-Jato, J.L., and Alonso, M.J., Design of microencapsulated chitosan microspheres for colonic drug delivery, J. Contr. Rel, 52 109-118 (1998). 

Demirel M. et al.. Formulation and in vitro-in vivo evaluation of piribedil solid lipid micro- and nanoparticles, J. Microencapsulation, 18, 359, 2001. 

Sugar-coated products have been marketed that contain KCl in a wax matrix (Slow-K and Kaon-Ct) and are purportedly slow- and controlled-release preparations. Available evidence indicates that these slow-release forms of KCl are occasionally capable of causing local tissue damage and therefore prol5ably should be used with caution for K+ supplementation. Solutions of potassium gluconate, like the tablets, also have been associated with intestinal ulceration. Microencapsulated KCl preparations Micro-K, K-Dur) that are neither enteric coated nor contained within a wax matrix appear to be superior to the wax matrix formulation. 

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