Controlled release drug delivery systems membranes

Controlled-release drug delivery systems mimic nature. Molecules called lipids are found in fats and also form the membranes of living cells. A lipid molecule is similar in struc-... 

Stancell et. al. ( 0) reported the possible use of ultrathin films deposited onto relatively permeable substrates as permselective membranes. Ultrathin and highly crosslinked coatings effectively distinguish between molecules of different sizes and increase the permselectivity of the substrate film. Chang et. al. ( ) demonstrated that the permeability coefficient of silicone rubber to oxygen decreased noticeably after depositing a plasma-polymerized ethylene film on the surface. Colter, et. al. (92.93) found similar effects of plasma polymerized films as diffusion barriers in controlled-released drug delivery systems. 

Membranes can be thought of as special types of films that provide specific end use characteristics. Membrane technology has replaced some conventional techniques for separation, concentration or purification [78]. Applications include desalination, dialysis, blood oxygenators, controlled release drug delivery systems and gas separation. Processing of polymer films and membranes is well known to affect the morphology, which in turn affects the physical and mechanical properties. As is true for all films, membrane separation properties are based on both the chemical composition and the structure resulting from the process. Membranes are produced in two major forms, as flat films and as porous hollow fibers, both of which will be discussed in this section. 

Good, W. R., and Lee, P. I. Membrane-controlled reservoir drug delivery systems, in Medical Applications of Controlled Release, ed. R. S. Langer and D. L. Wise, Vol. I. Boca Raton, CRC Press, 1984, pp. 1-39. 

Figure 18.6 Schematic drawing illustrating drug release from membrane controlled drug delivery systems (membrane diffusion systems and osmeotic systems).

A.J. McHugh, The role of polymer membrane formation in sustained release drug delivery systems. Journal of Controlled Release, 109,211-221, 2005. 

The majority of controlled drug delivery systems now being marketed or under development are based on diffusion of the drug through a semipermeable membrane to achieve the requisite release rate. Diffusion control is particularly important to transdermal delivery, where biodegradation and dissolution are not viable mechanisms of controlling the release rate. Provided the process is Fickian, the rate of diffusion through the semipermeable polymer is determined by... 

Elchidana, P. A., and Deshpande, S. G. (1999), Microporous membrane drug delivery system for indomethacin, I. Controlled Release, 59,279-285. 

Fig. 27.5. Mesoporous silica nanoparticles as novel drug delivery systems, (a) Cocondensation method to form functionalized mesoporous silica structures in a surfactant template synthesis, (b) TEM image of mesoporous silica nanoparticles and sketch of a novel drug delivery particle which contains functionalized pores, closed by a gate, and is decorated with ligands for cell targeting, (c) Cell targeting by ligand-receptor interaction at the cell membrane, endosomal uptake and controlled release after pH change from early to late endosome...

Fig. 3 Release of drug from various shapes of pol5mer membrane permeation-controlled drug-delivery systems (A) sphere-type, (B) cylinder-type, and (C) sheet-type. In (D), the drug concentration gradients across the rate-controlling polymeric membrane and hydrodynamic diffusion layer exist in series. Both the polymer membrane, which is either porous or non-porous, and the diffusion layer have a controlled thickness and h, respectively).

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