Controlled release from liposomes

The second diffusion problem, desorption from oil-water multilaminates, is considered as a model for (a) controlled release from liposomes and lipid multilayers and (b) for transport through biological laminates such as stratum corneum. In contrast to nonsteady-state transport across multilaminates, desorption from laminates depends only on the outermost layers. 

Desorption from an oil-water multilaminate should be an accurate model for controlled release from liposomes and lipid multilayers and may be helpful to understand transport through naturally occurring biological laminates such as stratum corneum. Asymptotic solutions based upon simple assumptions about the concentration profile may also be used to understand the desorption properties. 

Paasonen, L., Laaksonen, T., Johans, C., Yliperttula, M., Kontturi, K., and Urtti, A. (2007). Gold nanoparticles enable selective light-induced contents release from liposomes. J Controlled Release 122 86-93. 

Chandaroy P, Sen A, Hui SW (2001) Temperature-controlled content release from liposomes encapsulating Plutonic F127. J Control Release 76 27-37... 

Other surface-active compounds self-assemble into bilayer structures (schematically illustrated in Fig. 10b), which normally spherilize into structures termed vesicles. When vesicles are formed from phospholipids, the term liposome is used to identify the structures, which also provide useful drug delivery systems [71]. Solutes may be dispersed into the lipid bilayer or into the aqueous interior, to be subsequently delivered through a variety of mechanisms. Liposomes have shown particular promise in their ability to act as modifiers for sustained or controlled release. 

Gabizon A, Goren D, Cohen R, Barenholz Y (1998) Development of liposomal anthracyclines from basics to clinical applications. Journal of Controlled Release 53 275-279. 

Polyelectrolytes have recently found application in the development of pH sensitive liposomal controlled release systems. This application arises from the fact that polyelectrolytes may be used both to stabilize liposomes, and to disrupt liposomes in a pH dependent manner. Although the use of liposomes in oral pharmaceutical compositions has been discussed [424], liposomes generally suffer from poor stability and are therefore prone to leakage of the entrapped active agents. To overcome this problem, several authors have stabilized the liposomes using polyelectrolytes. For example, Tirrell and coworkers have employed ionene [425], and polyethylene imine) [426] to stabilize liposomes. Similarly, Sato and coworkers have studied maleic acid copolymers [427], and Sumamoto and coworkers have studied liposomes [428] coated with polysaccharides. In related work, Kondo and coworkers have emphasized the use of carboxymethyl chitin to produce artificial red blood cells [429-435]. 

Abra, R.M., Mihalko, P.J., and Schreier, H. (1990). The effect of lipid composition upon the encapsulation and in vitro leakage of metaprotemol sulfate from 0.2 im diameter, extruded, multilamellar liposomes. J. Control. Release, 14, 71-78. 

FIGURE 13.5 (a) Visualization of a typical multilamellar ethosome containing 2% PL, 30% ethanol, and water by TEM (b) Entrapment of fluorescent probes by phopholipid vesicles as visualized by CSLM. Liposomes (a-c) or ethosomes (d-f) were prepared with one of three fluorescent probes rhodamine red (a, d), D-289 (b, e), or calceine (c, f). White represents the highest concentration of probe. (Reproduced from Touitou, E. et al., J. Control. Release, 65, 403, 2000. With permission from Elsevier.)... 

FIGURE 13.7 Reconstituted CLSM optical slices of the stratum corneum of the skin following skin delivery of FITC-Bac in vivo in SD rats. Comparison of skin permeation routes from systems containing 0.1% FITC-Bac following an 8 h skin exposure ethosomes vs. liposomes and hydroethanolic solution. (Reproduced from Godin, B. Touitou, E., J. Control. Release, 94, 365, 2004. With permission from Elsevier.)... 

Knepp, V.M., et al. 1988. Controlled drug release from a novel liposomal delivery system. 

Knepp, V.M., F.C. Szoka, and R.H. Guy. 1990. Controlled drug release from a novel liposome delivery system. II. Transdermal delivery characteristics. J Control Release 12 25. 

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