Osmotic engine

This push-pull system has been applied to a system containing a liquid formulation (called L-OROS ). A liquid drug layer and an osmotic engine, or push layer, are encased in a hard gelatin capsule surrounded by a semipermeable membrane. However, there is a barrier layer separating the drug layer from the push layer in order to prevent any interaction between the two. A laser-drilled orifice is set in the top of the drug layer. 

The Duros implant pump is a modified version of the Alzet miniosmotic pump which additionally contains a piston to control drug flow, between the osmotic engine and the drag resorvoir (Figure 4.18). 

Fig. 7. When such device is in contact with a solution or wet environment, the surrounding water molecules will diffuse across the membrane to the osmotic engine, which will increase the pressure inside the osmotic compartment. Then the piston will move forward to induce the gradual release of the dmg inside the drug reservoir through the outlet orifice. The water permeating flux is the most important parameter of such drug delivery system as it ultimately determines drug release rate.

J. H. van t Hoff already showed the possibility of conversion of a certain amount of chemical free energy into mechanical work. He also suggested a system of osmotic cells with pistons which converts free energy directly to work. Of course van t Hoff s theoretical osmotic engine had no similarity with the processes taking place in living muscles, where the motility is generated not by a difference of osmotic pressure, but by a pertinent assembly system of macromolecular compounds (proteins), which contracts and expands as the consequence of a chemical reaction. 

Biocatalysts in nature tend to be optimized to perform best in aqueous environments, at neutral pH, temperatures below 40 °C, and at low osmotic pressure. These conditions are sometimes in conflict with the need of the chemist or process engineer to optimize a reaction with respect to space-time yield or high product concentration in order to facilitate downstream processing. Furthermore, enzymes and whole cells are often inhibited by products or substrates. This might be overcome by the use of continuously operated stirred tank reactors, fed-batch reactors, or reactors with in situ product removal [14, 15]. The addition of organic solvents to increase the solubility of substrates and/or products is a common practice [16]. 

Wyn Jones, R.G. (1980). An assessment of quarternary ammonium and related compounds as osmotic effectors in crop plants. In Genetic Engineering of Osmoregulation, ed. D.W. Rains, R.C. Valentine and A. Hollaender, pp. 155-70. New York Plenum Press. 

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Alvarez, C.A., Aguerre, R., Gomez, R., Vidales, S., Alzamora, S.M., and Gerschenson, L.N. 1995. Air dehydration of strawberries Effects of blanching and osmotic pretreatments on the kinetics of moisture transport. J. Food Engineer. 25, 167-178. 

Barranco, C.R., Balbuena, M.B., Garcia, P.G., and Garrido Fernandez, A. 2001. Management of spent brines or osmotic solutions. J. Food Engineer. 49, 237-246. 

Brambilla, A., Maffi, D., Bertolo, G., and Torreggiani, D. 2000. Effect of osmotic dehydration time on strawberry tissue structure. In ICEF 8, Eight International Congress on Engineering and Food, Book of Abstracts , p. 211. Puebla, Mexico. 

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Erie, U. and Shubert, H. 2001. Combined osmotic and microwave-vacuum dehydration of apples and strawberries. J. Food Engineer. 49, 193-199. 

Ferrando, M. and Spiess, W.E.L. 2001. Cellular response of plant tissue during the osmotic treatment with sucrose, maltose and trehalose solutions. J. Food Engineer. 49, 115-127. 

Fito, P. 1994. Modelling of vacuum osmotic dehydration of food. J. Food Engineer. 22, 313-328. 

Fito, P. and Chiralt, A. 1997. Osmotic dehydration An approach of the modelling of solid food-liquid operations. In Food Engineering 2000 (P. Fito, E. Ortega-Rodriguez, and G.V. Barbosa-C novas, eds), pp. 231-252. Chapman Hall, New York. 

Fito, P., Chiralt, A., Betoret, N., Gras, M., Chafer, M., Martinez-Monzo, J., Andres, A., and Vidal, D. 2001b. Vacuum impregnation and osmotic dehydration in matrix engineering Application in functional fresh food development. J. Food Engineer. 49, 175-183. 

Ishikawa, M. and Nara, H. 1993. Osmotic dehydration of food by semipermeable membrane coating. In Advances in Food Engineering (R.P. Singh and M.A. Wirakartakusuman, eds), pp. 73-77. CRC Press, London. 

Kayamak-Ertekin, F. and Sultanglu, M. 2000. Modelling of mass transfer during osmotic dehydration of apples. J. Food Engineer. 46, 243-250. 

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Lazarides, H.N., Gekas, V., and Mavroudis, N. 1997. Apparent mass diffusivities in fruit and vegetable tissues undergoing osmotic processing. J. Food Engineer. 31, 315-324. 

Lazarides, H.N., Katsanidis, E., and Nickolaidis, A. 1995. Mass transfer kinetics during osmotic preconcentration aiming at minimal solid uptake. J. Food Engineer. 25, 151-166. 

Lewicki, P.P. and Lukaszuk, A. 2000. Effect of osmotic dewatering on rheological properties of apple subjected to convective drying. J. Food Engineer. 45, 119-126. 

Lo Scalzo, R., Papadimitriu, C., Bertolo, G., Maestrelli, A., and Torreggiani, D. 2001. Influence of cultivar and osmotic dehydration time on aroma profiles of muskmelon (cucumis melo, cv reticulatus naud) spheres. J. Food Engineer. 49, 261-264. 

Maltini, E., Torreggiani, D., Fomi, E., and Lattuada, R. 1990. Osmotic properties of fruit juice concentrates. In Engineering and Food Physical Properties and Process Control (W.L.E. Spiess and H. Schubert, eds), Vol. 1, pp. 567-573. Elsevier Science, London. 

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