Controlled Release: A Quantitative Treatment by Professor Liang-tseng Fan, Dr. Satish Kumar Singh (auth.)

By Professor Liang-tseng Fan, Dr. Satish Kumar Singh (auth.)

The notion of managed free up has attracted expanding cognizance during the last 20 years, with the functions of this expertise proliferating in assorted fields in­ cluding medication, agriculture and biotechnology. examine and developmental efforts with regards to managed free up are multiplying in either and academia. the cause of this extraordinary progress is apparent. using various biologically energetic brokers, similar to medications, fertilizers and insecticides, has develop into a vital part of contemporary society. in addition to using those reagents has advanced an understanding that their out of control software virtually unavoidably induces destructive results at the future health of people and their surrounding environments. To put off or reduce those damaging results necessitates the managed liberate of those chemical substances. furthermore, the managed unlock of drugs, no longer frequently thought of poisonous or unsafe, e.g., a few catalysts and meals, can improve their effectiveness. The quantity and diversity of managed unencumber platforms, differing of their actual and chemical make-up, are expanding quickly. Proliferation commonly calls for correlation, generalization and unification; it calls for either the improvement of underlying theories in their habit and the mechanistic interpretation in their functionality. This, in flip, calls for a statistical and mathematical (quantitative) therapy of the medical info and technical information relating them. A quantitative therapy may also facilitate the formula of tactics for computer-aided layout of those structures via a priori prediction in their according to­ formance for quite a few layout parameters.

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Controlled Release: A Quantitative Treatment

The concept that of managed unencumber has attracted expanding awareness during the last 20 years, with the functions of this expertise proliferating in varied fields in­ cluding drugs, agriculture and biotechnology. study and developmental efforts relating to managed unencumber are multiplying in either and academia.

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5 Q. 2 "e0> 0 ~ ::J (5 '"e n- Paraf fins 0 0> 0 163 u" (f) 40 60 80 100 140 120 160 180 Molar volume of penetrant Fig. 18. , 1960) pH K lEI c o e 3 e. • >. =c o 0 e 2 I. 94 7. 0 Concentration in aqueous phase (16 3M) Fig. 19. Dependence of the solubility of p-toluene sulfonic acid in nylon films on the concentration of acid in, and pH of, the aqueous phase (Wibrant and Sundelof, 1983) d) Active agent loading and other design factors. Apart from the factors discussed in the preceding subsections, which are in the most part fixed, once the choice of the polymer-active agent system has been made, there exist some additional parameters that can affect the release characteristics but which can be altered independent of the choice of the system.

Nn;l" 4C! +- n I L - - sin co m;O 2m +I mrx . 40 a) and the amount released by time t is Mt - A = DIII(C ml C m2 ) t - b 4C*b + ---Tn 1 co L m;O 2b ~ C ml cos "n +""'2 L... , [1- exp (-D m" n t/c')-)] + 1)2 n 2 t/b 2 ]}. 40 b) A is the total area of exchange surface. 44) are equivalent to the solution obtained by the steady state analysis, Eq. 30) for Cm2 = 0; however, a similar reduction is possible with Cm2 #- o. , Crank, 1975). The more general case where the initial concentration profile is a function of position in the membrane has also been briefly considered by Crank (1975).

10. 2 a 100 b 120 140 160 I Hour pretreatment 180 200 temp (OC) The thermal history of polymer affects its transport properties. An example is portrayed in Fig. 10 (a, b) (Byron and Dalby, 1987), for poly(vinyl alcohol) films preheated at various temperatures for different durations. , 1983, 1984). Another pretreatment effect besides thermal history is the molecular orientation of polymer chains and their directions relative to the direction of diffusive flow. The rate of penetration parallel to the orientation axis is less than the rate in a randomly oriented sample, which is, in turn, less than the rate perpendicular to the orientation axis.

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