Thin films pharmaceutical applications

Membrane transport represents a major application of mass transport theory in the pharmaceutical sciences [4], Since convection is not generally involved, we will use Fick s first and second laws to find flux and concentration across membranes in this section. We begin with the discussion of steady diffusion across a thin film and a membrane with or without aqueous diffusion resistance, followed by steady diffusion across the skin, and conclude this section with unsteady membrane diffusion and membrane diffusion with reaction. 

The basic research in the future should be oriented towards novel materials for use in carbon dioxide as a solvent. These materials may have important applications in the synthesis of polymers, pharmaceuticals and other commodity chemicals, in the formation of thin films and foams, in coatings and extracts, and in the manufacture of microelectronic circuits. The full deployment of these applications would result in significant reductions in both volatile emissions and aqueous- and organic liquid wastes in manufacturing operations. 

Polypyrrole thin film doped with glucose oxidase (PPy-GOD) has been prepared on a glassy carbon electrode by the electrochemical polymerization of the pyrrole monomer in the solution of glucose oxidase enzyme in the absence of other supporting electrolytes. The cyclic voltammetry of the PPy-GOD film electrode shows electrochemical activity which is mainly due to the redox reaction of the PPy in the film. Both in situ Raman and in situ UV-visible spectroscopic results also show the formation of the PPy film, which can be oxidized and reduced by the application of the redox potential. A good catalytic response to the glucose and an electrochemical selectivity to some hydrophilic pharmaceutical drugs are seen at the PPy-GOD film electrode. 

The mechanism of dissolution was proposed by Nernst (1904) using a film-model theory. Under the influence of non-reactive chemical forces, a solid particle immersed in a liquid experiences two consecutive processes. The first of these is solvation of the solid at the solid-liquid interface, which causes the formation of a thin stagnant layer of saturated solution around the particle. The second step in the dissolution process consists of diffusion of dissolved molecules from this boundary layer into the bulk fluid. In principle, one may control the dissolution through manipulation of the saturated solution at the surface. For example, one might generate a thin layer of saturated solution at the solid surface by a surface reaction with a high energy barrier (Mooney et al., 1981), but this application is not commonly employed in pharmaceutical applications. 

The thin film of adhesive applied costs only a few pence per 1,000 labels, plus labour costs. Plain paper is most widely used for glass, but can be applied to metal, particularly in the form of a complete wrap around label. Application can be by hand, semiautomatic or fully automatic methods. Speeds of 1,000 or more per minute can be achieved. Pharmaceutical labelling usually ranges from 10 to 300 per minute. 

Major Applications Liquid crystals, thin films, sensors, 2 sol-gel matrix, waveguides, " host-guest chemistry, 5 display device, corrosion inhibitor, 7 glass coatings, paints, wound dressing materials,2o pharmaceuticals, dental materials,22 measuring nucleic acid ... 

Cells exploit bilayer structures to create anatomical boimdaries, eg in the case of cell membranes which are composed of lipids, proteins, and carbohydrates. During the early 1960s researchers demonstrated that certain classes of lipids, especially phospholipids, could be used to form protein- and carbohydrate-free model membranes. Methods were developed for the preparation of supported bilayer lipid membranes (1), and it was discovered that dried thin films of phospholipids spontaneously hydrate to yield lipid vesicles (2). Vesicles have since then been used as model systems for fluid interfaces and biomembranes (3). Practical applications involving vesicles are in the area of cosmetics and pharmaceutics. 

In contrast to PPSu which is a new polyester, PCL is well-known and extensively studied polymer. It is also biocompatible and has found many applications in pharmaceutical technology and medicine. Thus, it was also an interesting idea to explore miscibility and biodegradation behavior of blends made of these two very important polyesters. PCL/PPSu blends with concentrations 90/10, 80/20, 70/30 and 60/40 w/w were prepared by solutioncasting [47]. Proper amounts of both polymers were dissolved in chloroform as common solvent, at room temperature. Sonication was applied in order to achieve complete dissolution and fine mixing of the components. The blends in the form of thin films (200-250 pm) were set up after solvent evaporation at room temperature, under a gentle air stream. They were characterized by DSC, WAXD, HNMR, SEM, and Tensile testing. Finally, their enzymatic hydrolysis was studied. The PCL/PPSu blend system however proved to be only partially... 

PCTFE in thin film form is useful for protection against moisture and finds wide application in pharmaceutical blister packaging, electrolmnines-cent lamps and liquid crystal displays. Due to its chemieal stability, PCTFE is also used in chemical industry in the form of tubes, valves, chemical tank liners, 0-rings, seals and gaskets. Because of excellent electrical resistance and water repulsion properties, PCTFE finds applications also in preparation of flexible printed circuit boards, insulation of wires and cables. 

In this paper we report the electrochemical polymerization of the PPy-GOD film on the glassy carbon (GC) electrode in enzyme solution without other supporting electrolytes and the electrochemical behavior of the synthesized PPy-GOD film electrode. Because the GOD enzyme molecules were doped into the polymer, the film electrode showed a different cyclic voltammetric behavior from that of a polypyrrole film doped with small anions. The film electrode has a good catalytic behavior to glucose, which is dependent on the film thickness and pH. The interesting result observed is that the thin PPy-GOD film electrode shows selectivity to some hydrophilic pharmaceutical drugs which may result in a new analytical application of the enzyme electrode. 

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