Microcapsule preparation

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. 

Levy, M. C. Andry, M. C. (1990). Microcapsules prepared through interfacial cross-linking of starch derivatives. International Journal of Pharmaceutics, Vol. 62,1, (July 1990), pp. (27-35), ISSN 0378-5173... 

Fig. 7.5 TEM image of microcapsules prepared theinsetcorrespondsto800nm. PLL/PGAlayers by LbL assembly of three bilayers of a PLL/PGA were assembled from a 0.05 M MES, pH 5.5 shell on catalase-loaded BMS spheres, following buffer. The MS spheres were dissolved usingHF/ removal ofthe BMS particle template (A). CLSM NH4F at pH 5. (Adapted from [82] with per-images of (PLL/PGA)3 microcapsules loaded mission of Wiley-VCH). with FITC-labeled catalase (B). The scale bar in...

In vitro dissolution at increasing pH allows a comparison to be made between the different microcapsules prepared with various core wall ratios. The drug dissolution from the microcapsules depends on the core coat ratio and the rate of drug release decreases with a decrease in core coat ratio. 

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. 

Enzyme micro-encapsulation is another alternative for sensor development, although in most cases preparation of the microcapsules may require extremely well-controlled conditions. Two procedures have usually been applied to microcapsule preparation, namely interfacial polymerization and liquid drying [80]. Polyamide, collodion (cellulose nitrate), ethylcellulose, cellulose acetate butyrate or silicone polymers have been employed for preparation of permanent micro capsules. One advantage of this method is the double specificity attributed to the presence of both the enzyme and the semipermeable membrane. It also allows the simultaneous immobilization of many enzymes in a single step, and the contact area between the substrate and the catalyst is large. However, the need for high protein concentration and the restriction to low molecular weight substrates are the important limitations to this approach. 

Raez, I., Dredan, J., Antal, I., and Gondar, E. (1997). Comparative evaluation of microcapsules prepared by fluidization atomization and melt coating process. Drug Develop. Industrial Pharma. 23, 583-587. 

Lee, S.J., and Rosenberg, M. (2000). Whey protein-based microcapsules prepared by double emulsification and heat gelation. Lebensm. Wiss. Technol. 33, 80-88. 

Bachtsi, A.R. Kiparissides, C. Synthesis and release studies of oil-containing poly(vinyl alcohol) microcapsules prepared by coacervation. J. Controlled Release 1996, 38 (1), 49-58. 

Whateley, T.L. Microcapsules preparation by interfacial polymerization and interfacial complexation and their application. In Microencapsulation Methods and Industrial Applications Benita, S., Ed. Dekker New York, U.S.A., 1996 Vol. 73, 349-375. 

Sah, H.K. Toddywala, R. Chien, Y.W. Biodegradable microcapsules prepared by a w/o/w technique effects of shear force to make a primary w/o emulsion on their morphology and protein release. J. Microencapsul. 1995, 12 (1), 59-69. 

Dibutyl sebacate is used in oral pharmaceutical formulations as a plasticizer for film coatings on tablets, beads, and granules, at concentrations of 10-30% by weight of polymer. It is also used as a plasticizer in controlled-release tablets and microcapsule preparations. 

Deasy PB, O Connell MJM. Correlation of surface characteristics with ease of production and in vitro release of sodium salicylate from various enteric coated microcapsules prepared by pan coating. ] Micoencapsul 1984 1(3) 217—227. 

Journal of Microencapsulation 18, No.6, Nov./Dec. 2001, p.801-9 MORPHOLOGY AND STRUCTURE OF MICROCAPSULES PREPARED BY INTERFACIAL POLYCONDENSATION OF METHYLENE BIS(PHENYL ISOCYANATE) WITH HEXAMETHYLENE DIAMINE Jabbari E... 

Ogawa, Y., et al. In vivo release profiles of leuprolide acetate from microcapsules prepared with polylactic acids or copoly(lactic/glycolic) acids and in vivo degradation of these polymers. Chem. Pharm. Bull. (Japan), 1988, 36, 2576-2581. 

An improvement of medical materials on the base of biopolymers by encapsulating different dmgs opens up the wide prospects in applications of new devices with pharmacological activity. The design of injection systems for sustained dmg delivery in the forms of microspheres or microcapsules prepared on the base of biodegradable polymers is extremely ehallenging in the modem pharmaeology. 

Drusch S, Berg S (2008) Extractable oil in microcapsules prepared by spray-drying Localisation, determination and impact on oxidative stability. Food Chemistry 109 17-24. doi 10.1016/j.foodchem.2007.12.016. 

Y. Senuma, C. Lowe, Y. Zweifel, J. G. Hilbom, and I. Marison. Alginate hydrogel micro-spheres and microcapsules prepared by spinning disk atomization. Biotechnology and Bioengineering, 67(5) 616-622, 2000. 

Microencapsulation with complex coacervation has many advantages. It can produce capsules with a payload as high as 95%. The wall of the microcapsules is non-water soluble when it is either cross-linked with chemicals or treated with heat. This is a significant advantage over the microcapsules prepared with other technologies, such as spray drying or fluid bed coating by which the microcapsule wall produced is often water soluble. The microcapsules produced have excellent oxidation stability at low relative humidity, and core release can be initiated by different mechanisms. 

Figure 15.2 is a microscope image of the polyurea microcapsule prepared through a similar process. 

In most cases, anionic water-soluble polymers such as poly(styrene-maleic anhydride), polyacrylic acid, etc., are apphed. These kinds of emulsifiers can influence the microcapsule preparation, mean particle size, and particle size distribution. By emulsification, an electric double layer generates on the dispersed phase. Then the electrostatic interactions between the protonated amino resin prepolymer and the negatively charged orgaific phase can act as a driving force, which enable the wall material polycondensate on the surface of the oil droplets but not throughout the whole water phase. ... 

Zhang, B. Fei, X. Eu, Y. Yu, M. Zhao, H. Self-bonded double-waUed essence microcapsule preparation and application. CN 103230766, 2013. 

In 2010, Wang s and Fang s teams in China independently showed that PCM with enhanced thermal conductivity and phase-change performance can be successfully fabricated by sol-gel microencapsulation of wax such as n-octadecane and paraffin in silica microspheres obtained from TEOS polycondensation. The thermal conductivity of the microencapsulated n-octadecane is also significantly enhanced due to the presence of the high thermally conductive silica shell. However, the silica microcapsules prepared from TEOS only have poor mechanical properties, with the brittle shell of the microencapsulated PCM easily cracking. 

Capsules were porous on its surface (Figure 19.7a). On the other hand, cross-section of the microcapsules with vanillin showed that microcapsules prepared by using pure water as precipitation bath had macrovoids in their wall. This feature can be observed in Figure 19.7b). Fundamentals of the precipitation technique provide a suitable explanation for this phenomenon, as it has been explained before. When affinity between solvent and nonsolvent is high, as it is the case of DMF and water, a fast demixing of the solution will take place. Fast demixing has been observed to favor the apparition of macrovoids. 

Ritthidej, G.C. Tiyaboonchai, W. Formulation and drug entrapment of microcapsules prepared from chitosan-carboxymethylcellulose complex coacervation. Thai. J. Pharm. Sci. 1997, 21 (1), 137-144. 

The literature studies reported different factors affecting microcapsules preparation, such as concentration of alginate, hardening bath, gelation time, as weU as concentration of probiotic bacteria. 

On the other hand, literature studies report that the survivability and stability of probiotic bacteria loaded into chitosan-coated alginate microcapsules are largely dependent on the molecular weight of chitosan. ° Thus, the microcapsules prepared with high molecular weight chitosan provided a higher survival rate (46%) compared with the microcapsules made with low molecular weight chitosan (36%). ... 

FIGURE 36.13 Optical photomicrographs of proanthocyanidin microcapsules (a) prepared at pH 9.8, (b) prepared at pH 11 (same magnification). (Reprinted from/ t. /. Pharm., 171(2), Andry, M.-C., Vezin, H., Dumistracel, L, Bernier, J.L., and Levy, M.-C., Proanthocyanidin microcapsules Preparation, properties and free radical scavenging activity, 217-226. Copyright 1998, with permission from Elsevier.)... 

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