Capsule membrane shapes

Similar to studies on the porosity of capsule membranes using series of tracer molecules of different size, one may use molecules of similar size which differ in a single other parameter like polarity, shape, flexibility, etc., to yield additional information about the membrane structure. As all these observations are performed in the state of equilibrium distribution, there are no restrictions in terms of the overall duration of the measurement. Overall, systematic studies on the membrane permeability could elucidate a variety of details on the capsule structure and the possible release properties. 

Membrane shape. Flat sheet, hollow fiber, and hollow capsule. 

Table 2 indicates that the most suitable capsular membranes comprised semi-or non-transparent systems. Generally, the multicomponent blending resulted in smooth capsules with the exception of the alginate/spermine-polymethylene-co-guanidine systems which were either irregularly shaped or mosaic. There was no correlation observed between the capsule turbidity and permeability. 

The products can have a variety of shapes, such as spherical, oblong or irregular, can be monolithic or aggregates, and can have single or multiple walls. In Fig. 20.1 some typical morphologies of capsules are shown. The capsules consist of the coated or entrapped materials referred to as active, core material, fill, internal phase or payload (such as aroma chemicals). The coating or matrix material is called wall, membrane, carrier, shell or capsule. 

The ORO 5 Push-Stick technology is designed to deliver high doses of poorly water-soluble or slowly dissolving drugs at a controlled rate [50,52], The basic system consists of two layers, typically in a capsule-shaped tablet surrounded by a semipermeable membrane however, the system... 

The types of systems that can be produced using micelle formation include spheres, shells, capsules, vesicles, clusters, and particles of various shapes and sizes, such as spheres, rods, planar structures, and layered structures. Further processing can be undertaken to add rate-controlling polymer membranes to the outer shell and to incorporate different molecules to the surface (e.g., for receptor recognition). 

The snail-shaped cochlea, located in the temporal bone of the skull, contains a bony labyrinth and a membranous labyrinth. The bony labyrinth consists of the otic capsule (the external shell) and the modiolus (the internal axis). The membranous labyrinth, coiled inside the bony labyrinth, consists of three adjacent tubes the scala vestibuli, the scala media, and the scala tympani (O Figure 4-1). The scala vestibuli and the scala media are separated by Reissner s membrane the scala media and the scala tympani are separated by the basilar membrane and part of the osseous spiral lamina. The scala vestibuli and the scala tympani are filled with perilymph, a fluid whose ionic composition is similar to that of cerebrospinal fluid. The fluid sealed inside the scala media, the endolymph, contains a high concentration of potassium. 

A method by which small portions of liquids, particulate solids, or gases are enclosed by a shell (membrane, capsule) to form a dry, free flowing product often with spherical particle shape. The capsule shell may provide specific product characteristics (e.g. dispersibility, solubility). 

Figure 1 (A) Carrier-bound immobilized enzymes of defined size and shape. Insoluble carriers vary in iheir geometric parameters. Different shapes and types of enzyme carrier are illustrated (a) bead, (b) fiber, (c) capsule, (d) film, and (e) membrane. (B) Methods used for immobilizing enzymes onto a spherical solid support matrix 1, physical absorption 2, covalent binding 3, electrostatic binding 4, intermolecular cross-linking 5, gel entrapment 6, chelation and/or metal binding. E, enzyme M, metal.

Physical Methods. Physical methods are divided into two general approaches. The pesticide is entrapped within a physical structure either at a molecular or micro-domain level or the pesticide in the form of a reservoir is enclosed within a polymeric envelope (2). In the first approach, the pesticide is mixed with the polymer (or other material with high energy density) to form a monohthic structure or matrix. Release is normally through diffusion through the matrix or dissolution and erosion of the matrix. In the second approach, structures are based upon a reservoir of the pesticide enclosed by the polymer, from nano-scale up to centimeter-sized devices. The shapes of these devices are varied and include spherical, such as microcapsules, and laminar or layered structures with the reservoir bounded by permeable membranes. These membranes provide a permeable barrier which controls the release rate. Other mechanisms of release include capsule rupture and erosion of the membrane. 

A variety of molds are available to encapsulate samples for embedding. BEEM type capsules are useful for small pieces of materials that can be placed in the tip which then provides pretrimmed specimen blocks. Gelatin capsules are rounded in shape and thus must be trimmed, but they have the advantage that they can be removed by soaking in water. Other shapes are good for specific sample forms. Flat embedding molds are excellent for films and membranes. 

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