Membrane lipid rafts (i.e., cholesterol/sphingolipids domains) exhibit functional roles in both healthy and pathological states of the nervous system. However, due to their highly dynamic nature, it remains a challenge to characterize the fundamental aspects of lipid rafts that are important for specific neuronal processes. An experimental approach is presented here that allows for the interfacing of living neurons with an experimentally accessible model membrane where lipid order in cellular rafts can be reproducibly mimicked. It is demonstrated that coexisting lipid microdomains in model membranes can regulate axonal guidance and establish stable presynaptic contacts when interfaced with neurons in vitro. Experimental evidence is provided where specific functional groups and lateral organizations are favored by neurons in establishing synaptic connections. The model membrane platform presented in this work provides an accessible and direct means to investigate how lipid rafts regulate synapse formation. This experimental platform can similarly be extended to explore a variety of other cellular events where lipid lateral organization is believed to be important.

Neuropeptides are small neuronal signaling molecules that act as neuromodulators for a variety of neural functions including analgesia, reproduction, social behavior, learning, and memory. One of the endogenous neuropeptidesMet-Enkephalin (Met-Enk), has been shown to display an inhibitory effect on cell proliferation and differentiation. Here, a novel lipid-modification approach is shown to create a small library of neuropeptides that will allow increased bioavailability and plasma stability after systemic administration. It is demonstrated, on an experimental model of human pancreatic adenocarcinoma, that lipid conjugation of Met-Enk enhances its tumor suppression efficacy compared to its nonlipidated counterparts, both in vitro and in vivo. More strikingly, the in vivo studies show that a combination therapy with a reduced concentration of Gemcitabine has suppressed the tumor growth considerably even three weeks after the last treatment.

Spherically supported bilayer lipid membranes (SS-BLMs) exhibiting co-existing membrane microdomains were created on spherical silica substrates. These 5 μm SiO2-core SS-BLMs are shown to interact dynamically when interfaced with living cells in culture, while keeping the membrane structure and lipid domains on the SS-BLM surface intact. Interactions between the SS-BLMs and cellular components are examined via correlating fluorescently labeled co-existing microdomains on the SS-BLMs, their chemical composition and biophysical properties with the consequent organization of cell membrane lipids, proteins, and other cellular components. This approach is demonstrated in a proof-of-concept experiment involving the dynamic organization of cellular cytoskeleton, monitored as a function of the lipid domains of the SS-BLMs. The compositional versatility of SS-BLMs provides a means to address the relationship between the phenomenon of lipid phase separation and the other contributors to cell membrane lateral heterogeneity.

To understand the molecular anatomy of myelin membranes, we performed a large‐scale, liquid chromatography‐coupled tandem mass spectrometry (LC‐MS/MS)‐based lipidome and proteome screen on freshly purified human and murine myelin fractions. We identified more than 700 lipid moieties and above 1,000 proteins in the two species, including 284 common lipids and 257 common proteins. This study establishes the first comprehensive map of myelin membrane components in human and mice. Although this study demonstrates many similarities between human and murine myelin, several components have been identified exclusively in each species. Future quantitative validation studies focused on interspecies differences will authenticate the myelin membrane anatomy. The combined lipidome and proteome map presented here can nevertheless be used as a reference library for myelin health and disease. © 2012 Wiley Periodicals, Inc.

The ultrastructural details of presynapses formed between artificial substrates of submicrometer silica beads and hippocampal neurons are visualized via cryo-electron microscopy (cryo-EM). The silica beads are derivatized by poly-d-lysine or lipid bilayers. Molecular features known to exist at presynapses are clearly present at these artificial synapses, as visualized by cryo-EM. Key synaptic features such as the membrane contact area at synaptic junctions, the presynaptic bouton containing presynaptic vesicles, as well as microtubular structures can be identified. This is the first report of the direct, label-free observation of ultrastructural details of artificial synapses.

The development of gold nanorod plasmonic sol–gel polymer is presented and characterised with respect to its sensitivity to refractive index change. Structural characterisation of the polymer was conducted using Raman microscopy and energy dispersion spectroscopy while plasmonic function was investigated using UV/VIS spectroscopy. Refractive index sensitivities utilising the peak wavelength shift of the localised surface plasmon resonance were shown to be of the order of 2,338 nm per refractive index unit; in addition, peak absorbance was considered as an alternative measure. Furthermore, demonstration of sensitivity to biomolecule interaction has been shown as a model study. Strong photoluminescence was observed during Raman studies that restricts the potential use of the polymer as a surface-enhanced Raman substrate.

The difficulty in developing successful treatments to facilitate nerve regeneration has prompted a number of new in vitro experimental methods. We have recently shown that functional presynaptic boutons can be formed when neuronal cells are cocultured with surface-modified artificial substrates including poly(d-lysine)-coated beads and supported lipid bilayer-coated beads (Lucido(2009) J. Neurosci.29, 12449-12466; Gopalakrishnan(2010) ACS Chem. Neurosci.1, 86-94). We demonstrate here, using confocal microscopy combined with immunocytochemistry, that it is possible to isolate such in vitro presynaptic endings in an exclusive fashion onto glass substrates through a simple "sandwich/lift-off" technique (Perez(2006) Adv. Funct. Mater.16, 306-312). Isolated presynaptic complexes are capable of releasing and recycling neurotransmitter in response to an external chemical trigger. These bead-presynaptic complexes are facile to prepare and are readily dispersible in solution. They are thus compatible with many experimental methods whose focus is the study of the neuronal presynaptic compartment.

The formation of functional synapses on artificial substrates is a very important step in the development of engineered in vitro neural networks. Spherical supported bilayer lipid membranes (SS-BLMs) are used here as a novel substrate to demonstrate presynaptic vesicle accumulation at an in vitro synaptic junction. Confocal fluorescence microscopy, cryo-transmission electron microscopy (cryo-TEM), and fluorescence recovery after photobleaching (FRAP) experiments have been used to characterize the SS-BLMs. Conventional immunocytochemistry combined with confocal fluorescence microscopy was used to observe the formation of presynaptic vesicles at the neuron-SS-BLM contacts. These results indicate that lipid phases may play a role in the observed phenomenon, in addition to the chemical and electrostatic interactions between the neurons and SS-BLMs. The biocompatibility of lipid bilayers along with their membrane tunability makes the suggested approach a useful "toolkit" for many neuroengineering applications including artificial synapse formation and synaptogenesis in vivo.

CNS synapse assembly typically follows after stable contacts between “appropriate” axonal and dendritic membranes are made. We show that presynaptic boutons selectively form de novo following neuronal fiber adhesion to beads coated with poly-d-lysine (PDL), an artificial cationic polypeptide. As demonstrated by atomic force and live confocal microscopy, functional presynaptic boutons self-assemble as rapidly as 1 h after bead contact, and are found to contain a variety of proteins characteristic of presynaptic endings. Interestingly, presynaptic compartment assembly does not depend on the presence of a biological postsynaptic membrane surface. Rather, heparan sulfate proteoglycans, including syndecan-2, as well as others possibly adsorbed onto the bead matrix or expressed on the axon surface, are required for assembly to proceed by a mechanism dependent on the dynamic reorganization of F-actin. Our results indicate that certain (but not all) nonspecific cationic molecules like PDL, with presumably electrostatically mediated adhesive properties, can effectively bypass cognate and natural postsynaptic ligands to trigger presynaptic assembly in the absence of specific target recognition. In contrast, we find that postsynaptic compartment assembly depends on the prior presence of a mature presynaptic ending.

Spherical supported bilayer membranes (SS-BLMs) are very attractive candidates in modern bioanalytics and biorecognition studies. A uniform, facile method of preparing different SS-BLMs on silica beads is reported. Confocal fluorescence microscopy and cryo-TEM imaging have been used to characterize these SS-BLMs. Thermal analysis data and FRAP experiments show that the bilayer properties of the SS-BLM are consistent with those of lipid vesicles from which they are formed. The possibility of modulating the size, lipid type and functionality, and mechanical stability makes these rigid liposomes very attractive candidates in biosensors, drug screening, and gene delivery-related applications. This is especially true in work with native vesicle membranes derived from living cells because the existing methods can only accommodate anionic membranes to a limited extent.

The central goal of this thesis work is to fabricate novel, functional fluorescent nanostructures in confined systems offered by phospholipid membranes, which are known to have highly ordered, thermotropic and lyotropic structures. In separate approaches, we have used three different lipid systems: multilamellar planar lipid membranes, unilamellar vesicular membranes as well as lipid monolayers for the development of functional fluorescent nano-, micro- and meso-scopic structures. Techniques like fluorescence microscopy, single particle imaging, electron microscopy, electron diffraction were used to achieve fundamental understanding of the resulting structures. Multilayer stacks of phospholipid membranes have been used as an effective template for the growth of high aspect ratio fluorescent nanowires. The room temperature synthesis was achieved in the confined nanometer-sized interlamellar water space of lipid multilayers where supersaturating CdCl2 concentrations were induced by acidification leading to controlled unidirectional growth of nanowires. The possibility to render the nanowires fluorescent by doping with CdS quantum dots (QDs) and the light waveguiding along hundreds of micrometers together with the possibility of lateral manipulation make these nanowires attractive candidates for future optoelectronic applications. Novel organic-inorganic functional nanocontainers have been designed and tested by making use of vesicle forming lipid bilayers in combination with semiconductor QDs. Hydrophobic QDs can be integrated into bilayers of lipid vesicles and such lipid/QD hybrid vesicles are capable to fuse with live cells, thereby stain the cell's plasma membrane selectively with fluorescent QDs and transfer the vesicle's cargo into the cell. Modification of the membrane of such hybrid vesicles on the other hand, made them capable to enter the cytoplasm of live cells. Additionally, these hybrid vesicles were found extremely useful for long-term model membrane imaging studies. The results described in this thesis imply that cell and lipid membranes can integrate any kind of hydrophobic nanoparticle whose size matches the membrane thickness, opening novel possibilities to manipulate them as individuals or in ensemble with wide-ranging applications for nanobiotechnology. In a further step, the ability of phospholipid molecules to exhibit lamellar to non-lamellar transition using external stimuli enabled a directed self-assembly of QDs into mesoscale fluorescent structures. An easy and versatile method for the surface modification of TOPO coated CdSe QDs using 1,2-dipalmitoyl-sn-glycero-3-phosphatidic acid (DPPA) have been achieved. DPPA predominantly form non-lamellar phases when dispersed in water, for example, upon addition of Ca2+ or at a pH below 6 are known to form hexagonal II phases. This particular property of DPPA has been exploited to form mesoscale self-assemblies of QD based structures both in solution and in confined systems. Potential applications include the detection or removal of Ca2+ ions in attoliter volumes, the construction of functional devices where QDs are reversibly organized in different forms as well as use of fluorescently labeled DPPA molecules for cellular studies using fluorescence microscopy.

Angewandte Chemie International EditionVolume 45, Issue 33 p. 5478-5483 Communication Multifunctional Lipid/Quantum Dot Hybrid Nanocontainers for Controlled Targeting of Live Cells† Gopakumar Gopalakrishnan Dr., Gopakumar Gopalakrishnan Dr. Laboratoire de Chimie Physique des Polymères et Membranes, Institut des Sciences et Ingénierie Chimiques (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland, Fax: (+41) 21-693-6190Search for more papers by this authorChristophe Danelon Dr., Christophe Danelon Dr. Laboratoire de Chimie Physique des Polymères et Membranes, Institut des Sciences et Ingénierie Chimiques (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland, Fax: (+41) 21-693-6190Search for more papers by this authorPaulina Izewska, Paulina Izewska Laboratoire de Chimie Physique des Polymères et Membranes, Institut des Sciences et Ingénierie Chimiques (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland, Fax: (+41) 21-693-6190Search for more papers by this authorMichael Prummer Dr., Michael Prummer Dr. Laboratoire de Chimie Physique des Polymères et Membranes, Institut des Sciences et Ingénierie Chimiques (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland, Fax: (+41) 21-693-6190Search for more papers by this authorPierre-Yves Bolinger, Pierre-Yves Bolinger Laboratoire de Chimie Physique des Polymères et Membranes, Institut des Sciences et Ingénierie Chimiques (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland, Fax: (+41) 21-693-6190Search for more papers by this authorIsabelle Geissbühler Dr., Isabelle Geissbühler Dr. Laboratoire de Chimie Physique des Polymères et Membranes, Institut des Sciences et Ingénierie Chimiques (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland, Fax: (+41) 21-693-6190Search for more papers by this authorDavide Demurtas, Davide Demurtas Laboratoire d'Analyse Ultrastructurale (LAU), Université de Lausanne (UNIL), 1015 Lausanne, SwitzerlandSearch for more papers by this authorJacques Dubochet Prof. Dr., Jacques Dubochet Prof. Dr. Laboratoire d'Analyse Ultrastructurale (LAU), Université de Lausanne (UNIL), 1015 Lausanne, SwitzerlandSearch for more papers by this authorHorst Vogel Prof. Dr., Horst Vogel Prof. Dr. horst.vogel@epfl.ch Laboratoire de Chimie Physique des Polymères et Membranes, Institut des Sciences et Ingénierie Chimiques (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland, Fax: (+41) 21-693-6190Search for more papers by this author Gopakumar Gopalakrishnan Dr., Gopakumar Gopalakrishnan Dr. Laboratoire de Chimie Physique des Polymères et Membranes, Institut des Sciences et Ingénierie Chimiques (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland, Fax: (+41) 21-693-6190Search for more papers by this authorChristophe Danelon Dr., Christophe Danelon Dr. Laboratoire de Chimie Physique des Polymères et Membranes, Institut des Sciences et Ingénierie Chimiques (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland, Fax: (+41) 21-693-6190Search for more papers by this authorPaulina Izewska, Paulina Izewska Laboratoire de Chimie Physique des Polymères et Membranes, Institut des Sciences et Ingénierie Chimiques (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland, Fax: (+41) 21-693-6190Search for more papers by this authorMichael Prummer Dr., Michael Prummer Dr. Laboratoire de Chimie Physique des Polymères et Membranes, Institut des Sciences et Ingénierie Chimiques (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland, Fax: (+41) 21-693-6190Search for more papers by this authorPierre-Yves Bolinger, Pierre-Yves Bolinger Laboratoire de Chimie Physique des Polymères et Membranes, Institut des Sciences et Ingénierie Chimiques (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland, Fax: (+41) 21-693-6190Search for more papers by this authorIsabelle Geissbühler Dr., Isabelle Geissbühler Dr. Laboratoire de Chimie Physique des Polymères et Membranes, Institut des Sciences et Ingénierie Chimiques (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland, Fax: (+41) 21-693-6190Search for more papers by this authorDavide Demurtas, Davide Demurtas Laboratoire d'Analyse Ultrastructurale (LAU), Université de Lausanne (UNIL), 1015 Lausanne, SwitzerlandSearch for more papers by this authorJacques Dubochet Prof. Dr., Jacques Dubochet Prof. Dr. Laboratoire d'Analyse Ultrastructurale (LAU), Université de Lausanne (UNIL), 1015 Lausanne, SwitzerlandSearch for more papers by this authorHorst Vogel Prof. Dr., Horst Vogel Prof. Dr. horst.vogel@epfl.ch Laboratoire de Chimie Physique des Polymères et Membranes, Institut des Sciences et Ingénierie Chimiques (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland, Fax: (+41) 21-693-6190Search for more papers by this author First published: 11 August 2006 https://doi.org/10.1002/anie.200600545Citations: 196 † This work was supported by a grant (no. 4047-057562) from the NRP-47 program of the Swiss National Science Foundation and internal grants from the EPFL. We thank Marc Adrian (LAU, UNIL) for support with electron microscopy, and Ruud Hovius and Jean-Manuel Segura (LCPPM, EPFL) for helpful discussions. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Abstract Hydrophobic quantum dots can be incorporated into the bilayer membrane of lipid vesicles for selective delivery into either plasma membranes or the cytoplasm of living cells (see picture). The cell and lipid membranes can integrate any kind of hydrophobic nanoparticle whose size matches the membrane thickness, thus opening possibilities for their manipulation in nanobiotechnology applications. Citing Literature Supporting Information Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2006/z600545_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. Volume45, Issue33August 18, 2006Pages 5478-5483 RelatedInformation

Die Synthese nanoskopischer optischer Fasern aus CdCl 2 ⋅4 H 2 O mithilfe multilamellarer Lipidmembranen als Template beschreiben H. Vogel et al. in ihrer Zuschrift auf S. 5037 ff. Das Titelbild zeigt im Hintergrund einen Rasterelektronenmikrograph der Nanodrähte und von links nach rechts die Synthesestufen und die Lichtwellenleitung der Nanodrähte. Das Zentrum eines Nanodrahts wird bei 488 nm angeregt (grüner Laser), und orangefarbenes Licht wird am anderen Ende emittiert.

High-aspect-ratio, monocrystalline cadmium chloride nanowires doped with fluorescent CdS nanoparticles have been synthesized using planar lipid membranes as templates (see picture). Cd2+ ions bound to the lipid bilayers (a) are released at low pH to the nanometer-sized, interlamellar water films (b) where the sudden increase in concentration leads to the formation of nanowires (c) that show excellent light-waveguiding properties. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2005/z500386_s.html or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Nanoscopic optical fibers of CdCl2⋅4 H2O have been synthesized using multilamellar lipid membranes as templates. The cover picture shows a scanning electron micrograph of the nanowires in the background and, from left to right, the synthetic route and the optical waveguiding properties of the nanowires. The center of the nanowire is excited at 488 nm (green laser), and orange light is emitted from the other end. For more details, see the Communication by H. Vogel and co‐workers on page 4957 ff.

Copper and copper (I) oxide nanoparticles protected by self-assembled monolayers of thiol, carboxyl, and amine functionalities [X(CH(2))(n)-CH(3), where X can be -COOH, -NH(2), or -SH] have been prepared by the controlled reduction of aqueous copper salts using Brust synthesis. The optical absorption spectrum (lambda(max)=289 nm) is found to be invariant with the nature of the capping molecule while the particle shape and distribution are found to depend strongly on it. A comparison of the protection efficiency for different capping agents such as dodecanethiol (DDT), tridecylamine (TDA), and lauric acid (LA) suggests that although zerovalent Cu is initially formed for dodecanethiol, all other cases allow oxidation to Cu(2)O nanoparticles. Despite the variation in particle size and relative stability, nanoparticles have been found to form oxides after a few days, especially for the case of LA and TDA surface capping. For all the samples studied, the size has been found to be 4-8 nm by high-resolution transmission electron microscopy. The protective ability is found to be better for dodecanethiol SAM (similar to the case of Au and Ag nanoparticles), while the order of capping efficiency varies as Cu-DDT>Cu-TDA>Cu-LA. In the present study we also demonstrate a reversible metal-insulator transition (MIT) in capped nanoparticles of Cu using temperature-dependent electrical resistivity measurement. However, the LA-capped sample does not show any such transition, possibly due to the oxide formation.