Microencapsulation microcapsule

The oxidative stability of seal blubber oil (SBO) is improved by microencapsulation. Microcapsules containing SBO prepared with p-cyclodextrins as the wall material are easily handled and incorporated into food formulations [61]. 

Microencapsulation is the coating of small solid particles, liquid droplets, or gas bubbles with a thin film of coating or shell material. In this article, the term microcapsule is used to describe particles with diameters between 1 and 1000 p.m. Particles smaller than 1 p.m are called nanoparticles particles greater than 1000 p.m can be called microgranules or macrocapsules. 

Microcapsules are used in a number of pharmaceutical, graphic arts, food, agrochemical, cosmetic, and adhesive products. Other specialty products also exist, thus the concept of microencapsulation has been accepted by a wide range of industries. In order to illustrate how microcapsules are used commercially, it is appropriate to describe a number of commercial microcapsule-based products and the role that microcapsules play in these products. 

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). 

New Developments. Creation of microencapsulation technology and appHcations of microcapsules are goals that many research and... 

Carbonless Copy Paper. In carbonless copy paper, also referred to as pressure-sensitive record sheet, an acid-sensitive dye precursor, such as crystal violet lactone or /V-hen2oy11eucomethy1ene blue, is microencapsulated with a high boiling solvent or oil within a cross-linked gelatin (76,83,84) or in synthetic mononuclear microcapsules. Microcapsules that have a starch binder are coated onto the back of the top sheet. This is referred to as a coated-back (CB) sheet. The sheet intended to receive the image is treated on the front (coated-front (CF)) with an acid. When the top sheet is mechanically impacted, the dye capsules mpture and the dye solution is transferred to the receiving sheet where the acid developer activates the dye. 

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... 

In addition, Montenegro et al., (2007) determined that the photosensitized RF-mediated degradation of vitamins A, D3, and RF itself in skimmed milk was strongly reduced by the addition of small amounts of lycopene-gum arabic-sucrose microcapsules, prepared by spray-drying. Under these conditions, the bulk properties of the skimmed milk were unmodified. The main photoprotection mechanism of the milk vitamins was the efficient quenching of the 3Rf by the protein moiety of GA. Small contributions (<5%) to the total photoprotection percentage was due to both inner filter effect and 1O2 quenching by the microencapsulated lycopene. 

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. 

A method of the preparation of polylactic acid microcapsules of controlled particle size and drug loading, J. Microencapsul.,... 

Lin, S. Y., Ho, L. T., Chiou, H. L., Microencapsulation and controlled release of insulin from polylactic acid microcapsules. Biomater. Med. Devices Artif. Organs. 86, 187, 1985. 

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)... 

At present there is no reason evident why poly(N-acylhydroxy-proline esters) should not be suitable for the formation of microcapsules or microspheres as well. For microencapsulated drug fonmula-tions the longer degradation times of poly(N-acylhydroxyproline esters) as compared to poly (lactic acid) could again be a distinctive advantage for long-term applications. 

Pressure-sensitive recording materials are obtained by dissolving a triphenylmethane leuco dye in a solvent composed of paraffin oils. The microcapsules are formed from a water-soluble106 or water-dispersible material.107,108 Leuco dyes dissolved in sunflower oil are microencapsulated in a solution containing a melamine-HCHO precondensate and coated on the back side of a paper sheet. Contact of the microcapsule-coated sheet with an acid-coated receptor sheet allows the color formation to occur. 

Chen, H Wu, J.-C. and Chen, H.-Y. (1995) Preparation of ethylcellulose microcapsules containing theophylline by using emulsion non-solvent addition method. Journal of Microencapsulation, 12, 137-147. 

Polyamide, collodion (cellulose nitrate), ethylcellulose, cellulose acetate butyrate or silicone polymers have been used for preparation of permanent microcapsules. This method offers a double specificity due to the presence of both the enzyme and a semipermeable membrane. Moreover, it allows simultaneous immobilization of many enzymes in a single step and the surface area for contacting the substrate and the catalyst is large. The need of high protein concentration and the restriction to low molecular weight substrates are the main limitations of enzyme microencapsulation. 

Sjovall J, Sjoqvist R, Huitfeldt B, Nyqvist H. Correlation between the bioavailability of microencapsulated bacampicillin hydrochloride in suspension and in vitro microcapsule dissolution. J Pharm Sci 1984 73 141—145. 

Dragan D, Carpov A. 1987. Microencapsulated organophosphorous insecticides. III. Some aspects on the volatilization of malathion and disulfoton from aqueous suspensions of microcapsules. Microencapsul 4 97-105. 

Various techniques have been developed for the preparation of microcapsules with diameters of 1-5000 pm one of these involves the method of interfacial polycondensa-tion.The following example describes the microencapsulation of a dyestuff, which has practical application in the manufacture of carbon-free copy paper. 

Voigt A, Lichtenfeld H, Sukhomkov GB, Zastrow H, Donath E, Baumler H, Mohwald H. Membrane filtration for microencapsulation and microcapsules fabrication by layer-by-layer polyelectrolyte adsorption. Ind Eng Chem Res 1999 38 4037-4043. 

Several other investigators have reported microencapsulation methods based upon polyelectrolyte complexes [289, 343]. For example, oppositely-charged polyelectrolytes (Amberlite IR120-P (cationic) and Amberlite IR-400 (anionic)) were recently used along with acacia and albumin to form complex coacervates for controlled release microcapsule formations [343]. Tsai and Levy [344,345] produced submicron microcapsules by interfacial crosslinking of aqueous polyethylene imine) and an organic solution of poly(2,6 dimethyl... 

Macro-coating is used mainly to stabilise fragrances or transform them from liquid to free-flowing solid powder. Microencapsulation or nanoencapsulation is the process of enclosing a substance inside a miniature capsule. These capsules are referred to as microcapsules or nanocapsules. The substance inside the capsule can be a gas, liquid or solid. The capsule wall can consist of various materials, such a wax, plastic or biopolymers like proteins or polysaccharides. 

The present study investigates a biodegradable polymer, poly(DL-lactic acid) (DL-PLA), as the microcapsule wall. Tablets of microcapsules prepared with this method should be capable of use as subcutaneous implants. Three different compression forces, 2, 5 and 10 kN, were used, with core wall ratios of 1 1 and 2 1. For comparison, the same proportions of drug and coating polymer were compressed without prior microencapsulation. 

The release of the drug phenobarbitone (PB) from tablets prepared using simple mixtures of DL-PLA and PB, as well as from the corresponding tablets from microencapsulated PB, is reported. These results are compared with release from the original microcapsules. 

Figure 2.3 Scanning electron micrographs of fish oil microcapsules which were microencapsulated with different concentrations of sugar beet pectin (A and D 1.1% B and C 2.2%) and different oil loads (A and C 50% B and D 20%). Reproduced from Dmsch (2007) with permission.

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