Elastic vesicles

FIGURE 13.3 The cumulative amount of ketorolac as a function of time from elastic and rigid vesicle formulations across human skin in vitro. Elastic vesicles were clearly more effective as compared with rigid vesicles in the enhancement of ketorolac transport across the skin. The cumulative amounts found after 1 and 4 h of elastic vesicle treatment (corresponding to the time periods chosen for this study), however, were still very low. (Reproduced from Honeywell-Nguyen, P.L. et al., J. Invest. Dermatol., 123, 902, 2004. With permission from Blackwell Publishing.)... 

Honeywell-Nguyen, P.L., and J.A. Bouwstra. 2003. The in vitro transport of pergolide from surfactant-based elastic vesicles through human skin A suggested mechanism of action. J Control Release 86 145. 

Honeywell-Nguyen, P.L., et al. 2003. The in vivo transport of elastic vesicles into human skin Effects of occlusion, volume and duration of application. J Control Release 90 243. 

Transfersomes are vesicles prepared from lipids and an edge activator that might be a single-chain lipid or surfactant. The edge activator renders the vesicles elastic. As a result of the hydration force in the skin, elastic vesicles can squeeze through SC lipid lamellar regions [47], Transfersomes were much more effective than conventional liposomes when applied nonocclusively with respect to mass flow of lipid across the skin. After 8 h of transfersome application... 

B. A. I. van den Bergh, J. Vroom, H. Gerritsen, H. E. Junginger, and J. Bouwstra. Interactions of elastic vesicles with human skin in vitro electron microscopy and two-photon excitation microscopy, Biochim. Biophys. Acta 7467 155-173... 

Recently, for the transdermal delivery of drugs using carrier systems, attention has been focused on the development of transformable [284,285] or elastic vesicles [12], These vesicles are liposomes that contain surfactants or in general edge activators in addition to phospholipids in their lipid membranes (Figure 10), a fact that... 

During recent years, the topical delivery of liposomes has been applied to different applications and in different disease models (188). Current efforts in this area concentrate around optimization procedures and new compositions. Recently, highly flexible liposomes called transferosomes that follow the trans-epidermal water activity gradient in the skin have been proposed. Diclofenac in transferosomes was effective when tested in mice, rats and pigs (189). The concept of increased deformability of transdermal liposomes is supported by the results of transdermal delivery of pergolide in liposomes, in which elastic vesicles have been shown to be more efficient (190).The combination of liposomes and iontophoresis for transdermal delivery yielded promising results (191, 192). 

Bouwstra JA, De Graaff A, Groenink W, Honeywell L (2002) Elastic vesicles interaction with human skin and drug transport. Cell Mol Biol Lett 7(2) 222-223... 

In the simplest model for analyzing the shape of elastic vesicles with thin fluid membranes, the bending energy is made proportional to the integrated curvatures over the closed membrane surface... 

Two papers have dealt with model membrane systems. Shintani and co-workers reported an NOE and MD simulation study of phospholipid aggregates in the form of micelles and vesicles. In the case of these systems, the usual approximation in the NOE analysis - separability of the information on distances and dynamics - are not applicable and the MD data provide an important support for the analysis of experimental data. Uchino et described characterization of rigid and elastic vesicles, loaded with the drug keterolac. Among other techniques, they applied T2 (really line-width) studies for suitable isolated proton spins in the drug. 

Fig. 32 Snapshots of vesicles in capillary flow, with bending rigidity K/k T = 20 and capillary radius / cap = 1-4/fo- a Fluid vesicle with discoidal shape at the mean fluid velocity v T/ffcap =41, both in side and top views, b Elastic vesicle (RBC model) with parachute shape at t m r/Rcap — 218 (with shear modulus nRl/ksT = 110). The blue arrows represent the velocity field of the solvent, c Elastic vesicle with shpper-like shape at v r/Rcap = 80 (with iiRl/k T = 110). The inside and outside of the membrane are depicted in red and green, respectively. The upper front quarter of the vesicle in (b) and the front half of the vesicle in (c) are removed to allow for a look into the interior, the black circles indicate the lines where the membrane has been cut in this procedure. Thick black lines indicate the walls of the cylindrical capillary. From [187]...

Fig. 33 Critical flow velocity Vm of the discocyte-to-parachute transition of elastic vesicles and of the discocyte-to-prolate transition of fluid vesicles, as a function of the bending rigidity for IdRl/ksT =110 (left), and of the shear modulus ju for k/UbT = 10 (right). From [187]...

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