Micro-capsules

BASF encapsulates different paraffins with a special process and sells the micro capsules under the brand name Micronal as fluid dispersion or as dried powder (Figure 118). 

Figure 117. Microscope image of an opened micro capsule (picture BASF/Germany)...

Capsules, controlled-release 600 mg potassium chloride equivalent to 8 mEq potassium. Microencapsulated particles (Rx) Micro-K Extencaps (Robins)... 

Containment Behind a Barrier Cells can be immobilized within micro-capsules that have either a permanent or nonpermanent semipermeable membrane. The advantage of encapsulation techniques is the large surface area for contact of substrate and cells. The semipermeable membrane also selectively passes only low-molecular weight components. 

The variety of materials which can be incorporated into polyelectrolyte multilayers makes them attractive to use as biosensors [431], Polyelectrolyte multilayers can also be formed on curved surfaces of small particles [432], After adsorption, the core particle can be chemically dissolved and a hollow polyelectrolyte capsule remains. These capsules are selectively permeable for small molecules like water or certain dyes. The permeability can be tuned externally by varying the ion strength, pH, temperature and solvent nature [433 135], Therefore, it has been suggested to use them as selective membranes for separation, as well as a possible drug delivery system. The adjustment of their size and permeability allows us to exploit them as micro- or nanocontainers for chemical synthesis and crystallization. 

Graham, D.Y., J.L. Smith, and A.A. Bouvet. 1990. What happens to tablets and capsules in the stomach Endoscopic comparison of disintegration and dispersion characteristics of two micro-encapsulated potassium formulations. J Pharm Sci 79 420. 

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. 

Transplantation of islets of Langerhans as a means of treating insulin-dependent diabetes mellitus has become an important field of interest [217-219]. However, tissue rejection and relapse of the initial autoimmune process have limited the success of this treatment. Immunoisolation of islets in semipermeable microcapsules has been proposed to prevent their immune destruction [220, 221]. Nevertheless, a pericapsular cellular reaction eventually develops around micro-encapsulated islets, inducing graft failure [222]. Since empty microcapsules elicit a similar reaction [223], the reaction is not related to the presence of islets within the capsule but is, at least partially, caused by the capsule itself. Consequently, microcapsule biocompatibility appears to constitute a major impediment to the successful microencapsulated islet transplantation. 

In Section II of this review, we describe the theoretical background and in Section III we give examples of practical applications to determine the micro-capsule structure by using a combination of different scattering techniques. We also touch on recent topics, such as scanning near field microscopy. 

Traditionally used in the meat industry sausage casing and meat preservation eariy proposed in patents disclosures (Harvard and Harmony 1869) various pharmaceutical and other food industry applications ingredients micro-encapsulation, tablets and capsules (Gennadios et al. 1994)... 

These additives can also be placed into microcapsules with a thin polymer skin. For example, they are filled with natural aromas and applied to the textile from a water dispersion in combination with a polyurethane or silicone binder. The ratio of micro bubbles to binder determines the efficiency and permanence of the finish. Good results after 4-12 washing cycles are reported. The encapsulated materials are released during wearing as the micro bubbles burst from rubbing caused by body movement or by diffusion through the thin layer of the capsules. A market available encapsulation in micro bubbles, built from chitosan, is described by Hampe. The incorporation and controlled release of fragrance compounds is also provided by the sol-gel nano-technique described in Section 18.4. 

Thu, B. Bruheim, P. Espevic, T. Smidsr0d, O. Soon-Shiong, P. Skjak-Braek, G. Alignate polycation micro-capsules. 1. Interaction between alginate and polycation. Biomaterials 1996, 17 (10), 1031-1040. 

Many solid-dosage forms of potassium chloride exist including tablets prepared by direct compression and granulation effervescent tablets coated, sustained-release tablets " sustained-release wax matrix tablets micro-capsules pellets and osmotic pump formulations. ... 

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