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<p><b>Overcoming semi-permeable barriers, such as the skin, with ultradeformable mixed lipid vesicles, Transfersomes® liposomes or mixed lipid micelles.</b></p> <p>G.Cevc, A.Schätzlein, H. Richardsen, U. Vierl</p> <p><b>Langmuir, 19, 10753-10763 (2003).</b></p> <p>We studied lipid aggregate penetration through nano-porous, semi-permeable barriers by direct transport measurements in vitro and with the confocal laser scanning microscopy of the skin in vivo. We found that it is necessary to use mixed lipid bilayers with a low resistance to permeabilisation and high flexibility to overcome narrow, normally confining pores. Partial molecular demixing in the stressed vesicle bilayer serves both purposes. An aggregate comprising a suitable blend of amphipats (Transfersome® Tfs) is therefore extremely deformable and crosses easily even very narrow pores (<i>r<sub>Tfs®</sub></i> ≥ 10 <i>r<sub>pore</sub></i>, and possibly more). Each such vesicle then behaves as a responsive, self-optimizing, nano-robotic transport device. The mixed micelles with identical components or the simple vesicles (liposomes) with a similar size as that of unusually deformable vesicles do not share this quality. Liposomes only traverse barriers when <i>r<sub>lipos</sub></i> ≤ 1.5<i>r<sub>pore</sub></i>; they clog narrower pores, unless they get fragmented in/before the orifice. Mammalian skin is perforated by a very large number (10<sup>7</sup> cm<sup>-2</sup>) of very narrow (<i>r<sub>pore</sub></i> ~ 0.3 nm) inter-cellular hydrophilic pores. These can be widened into the barrier spanning, hydrophilic transcutaneous pathways (<i>r<sub>pathway</sub></i> ~ 20-30 nm) by ultradeformable vesicles. Mixed micelles or liposomes do not activate such pores as they are, respectively, too small or too un-deformable (<i>κ<sub>lipos</sub></i> > 107nbsp;<i>κ<sub>Tfs</sub></I>) and large (<i>r<sub>lipos</sub></i>/nm ≥ 45 >> 20) for the purpose. The outer 2/3 of the skin barrier also contain fewer but wider openings (<i>r<sub>pore</sub></i>≥ 3 µm), which encircle groups of cells in the stratum corneum. The resulting sparse, low-resistance inter-cluster pathway can accommodate various sufficiently small aggregates (<i>r<sub>a</sub></i> ≤ 2 µm), including liposomes and micelles. All the tested lipidic particles can therefore reach locally ~60 % of the skin barrier depth, on the average. Ultradeformable vesicles move through the skin most uniformly and to greatest relative depth, however. Locally or near the skin surface the distribution of different lipid aggregates which penetrate a barrier can be similar.</p> <p><a href="index.html"><----</a> | <a href="../.././index.html" target="_top" onmouseover="putstattext('What is special about IDEA?'); return true;">Home</a> | <a href="../../about-us/index.html" target="_top" onmouseover="putstattext('About IDEA history, people, external collaboratory and future plans.'); return true;">About us</a> | <a href="../../corporate_factsheet/index.html" target="_top" onmouseover="putstattext('Corporate Factsheet'); return true;">Corporate Factsheet</a> | <a href="../../science/index.html" target="_top" onmouseover="putstattext('Academic collaborations, publications, etc.'); return true;">Science</a> | Publications | <a href="../../product_opportunities/index.html" target="_top" onmouseover="putstattext('IDEA offers better compliance, local drug targeting and patent protection.'); return true;">Product opportunities</a> | <a href="../../financial/index.html" target="_top" onmouseover="putstattext('Investors and basic financial data.'); return true;">Finance</a> | <a href="../../press_releases/index.html" target="_top" onmouseover="putstattext('Original texts.'); return true;">Press releases</a> | <a href="../../latest_newsletter/index.html" target="_top" onmouseover="putstattext('IDEAS latest newsletter'); return true;">Latest newsletter</a> | <a href="../../press_clippings/index.html" target="_top" onmouseover="putstattext('IDEA in the press.'); return true;">Press clippings</a> | <a href="../../conferences/index.html" target="_top" onmouseover="putstattext('Here you will find many dates where you can meet us and where we can talk...'); return true;">Conferences</a> | <a href="../../career/index.html" target="_top" onmouseover="putstattext('We constantly seek best talents and dedication, offering much in return.'); return true;">Career</a> | <a href="../../contact/index.html" target="_top" onmouseover="putstattext('We would like to hear from you!'); return true;">Contact</a> | <a href="../../faq/index.html" target="_top" onmouseover="putstattext('Product bio/acceptability, liposome/Transfersome, ...'); return true;">Scientific FAQ</a> | <a href="../../glossary/index.html" target="_top" onmouseover="putstattext(''); return true;">Glossary</a> | <a href="../../sitemap/index.html" target="_top" onmouseover="putstattext('Get an impression on IDEA!'); return true;">Site Map</a> | <a href="../../search/index.html" target="_top" onmouseover="putstattext('Find documents based on keywords!'); return true;">Search</a> |  </p>