Research

Permeability of lipid bilayers induced by polymers

Lipid bilayers emerge by self-organization of amphiphilic molecules and are the essential component of membranes of living cells. An important task of them is the selective exchange of substances between the cell and its environment. This becomes particularly interesting for delivering foreign molecules and RNA into the cell. In the classical view of cell biology static […]

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Selective bactericidal activity of nanopatterned superhydrophobic cicada Psaltoda claripennis wing surfaces

Appl Microbiol Biotechnol., 97 (20), 9257-9262 (2013)
Jafar Hasan, Hayden K. Webb, Vi Khanh Truong, Sergey Pogodin, Vladimir A. Baulin, Gregory S. Watson, Jolanta A. Watson, Russell J. Crawford, Elena P. Ivanova
The nanopattern on the surface of Clanger cicada (Psaltoda claripennis) wings represents the first example of a new class of biomaterials that can kill bacteria on contact […]

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IPEC Solver: Numerical simulation tool to study inter-polyelectrolyte complexation

Comp. Phys. Comm., 184 (9), 2221–2229 (2013)
B. Huang and V.A. Baulin

IPEC Solver is a Windows program designed to analyze the stability of core–shell inter-polyelectrolyte complexes formed by complexation of oppositely charged block copolymers. The two-dimensional size distribution of the complexes composed by different numbers of positively or negatively charged polyelectrolytes is calculated based on the […]

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Bacterial attachment on sub-nanometrically smooth titanium substrata

Biofouling, 29 (2), 163-170 (2013)
H.K. Webb, V. Boshkovikj, C.J. Fluke, V.K. Truong, J. Hasan, V.A. Baulin, R. Lapovok, Y. Estrin, R.J. Crawford and E.P. Ivanova
Despite the volume of work that has been conducted on the topic, the role of surface topography in mediating bacterial cell adhesion is not well understood. The primary reason for this lack of […]

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Size- and coating-dependent uptake of polymer-coated gold nanoparticles in primary human dermal microvascular endothelial cells

Christian Freese, Matthew I. Gibso, Harm-Anton Klok, Ronald E. Unger, C. James Kirkpatrick

Biomacromolecules, 13 (5), pp 1533–1543 (2012)

A library-orientated approach is used to gain understanding of the interactions of well-defined nanoparticles with primary human endothelial cells, which are a key component of the vasculature. Fifteen sequentially modified gold nanoparticles (AuNPs) based on three different core […]

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Interactions of silica nanoparticles with lung epithelial cells and the association to flotillins

Jennifer Kasper, Maria I. Hermanns, Christoph Bantz, Olga Koshkina, Thomas Lang, Michael Maskos, Christine Pohl, Ronald E. Unger, C. James Kirkpatrick

Arch. Toxicol., 6 (2012)

Amorphous silica nanoparticles (aSNPs) gain increasing popularity for industrial and therapeutic claims. The lung with its surface area of 100–140 m2 displays an ideal target for therapeutic approaches, but it represents also […]

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Uptake and cytotoxicity of citrate-coated gold nanospheres: Comparative studies on human endothelial and epithelial cells

Christian Freese, Chiara Uboldi, Matthew I Gibson, Ronald E Unger, Babette B Weksler, Ignacio A Romero, Pierre-Olivier Couraud, C J Kirkpatrick

Part Fibre Toxicol., 9, 23 (2012)

BACKGROUND:
The use of gold nanoparticles (AuNPs) for diagnostic applications and for drug and gene-delivery is currently under intensive investigation. For such applications, biocompatibility and the absence of cytotoxicity of AuNPs […]

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Diblock copolymer–selective nanoparticle mixtures in the lamellar phase confined between two parallel walls: a mean field model

Lenin S. Shagolsem, Jens-Uwe Sommer
Soft Matter, 8, 11328-11335 (2012)
We present a mean field model for a mixture of AB diblock-copolymers and A-block selective nanoparticles confined between two identical non-selective walls. A horizontally symmetric lamellar structure of the nanocomposite is considered where nanoparticles are allowed to segregate between the polymer–wall interfaces. For a fixed value of […]

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Mechanisms of Vesicle Spreading on Surfaces: Coarse-Grained Simulations

Marc Fuhrmans, Marcus Müller

Langmuir, 29 (13), pp 4335–4349 (2013)

Exposition of unilamellar vesicles to attractive surfaces is a frequently used way to create supported lipid bilayers. Although this approach is known to produce continuous supported bilayer coatings, the mechanism of their formation and its dependence on factors like surface interaction and roughness or membrane tension as […]

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Exploring thermodynamic stability of the stalk fusion-intermediate with three-dimensional self-consistent field theory calculations

Kostas Ch. Daoulas, Marcus Müller

Soft Matter, 9, 4097-4102 (2013)

The prospects of compressible Self-Consistent Field (SCF) theory schemes for describing structures in amphiphilic membranes are illustrated by considering the thermodynamic stability of hourglass-shaped, hydrophobic connections (stalks) between apposed bilayers. The membranes are represented by a coarse-grained, solvent-free model. We represent the chain architecture […]

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Biophysical Model of Bacterial Cell Interactions with Nanopatterned Cicada Wing Surfaces

S. Pogodin, J. Hasan, V.A. Baulin, H.K. Webb, V.K. Truong, T.H.P. Nguyen, V. Boshkovikj, C.J. Fluke, G.S. Watson, J.A. Watson, R.J. Crawford and E.P. Ivanova

Biophys. J., 104 (4), 835-840 (2013)

The nanopattern on the surface of Clanger cicada (Psaltoda claripennis) wings represents the first example of a new class of biomaterials that can kill bacteria […]

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Nanoparticle-Induced Permeability of Lipid Membranes

Sergey Pogodin, Marco Werner, Jens-Uwe Sommer, Vladimir A. Baulin

ACS Nano, DOI: 10.1021/nn3028858 (2012)

Monte Carlo simulations using the bond fluctuation method with explicit solvent reveal the mechanism of enhanced permeability of lipid bilayers induced by the adsorption of nanoparticles with controlled hydrophobicity. Simulation results indicate an adsorption transition of nanoparticles on the bilayer in a […]

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Poly-ethylene glycol induced super-diffusivity in lipid bilayer membranes

Thibault Tabarin, Aaron Martin, Robert J. Forster and Tia E. Keyes

Soft Matter, 8, 8743-8751 (2012)

Fluorescence lifetime correlation spectroscopy (FLCS) has been used to probe the influence of PEG-8000 on the fluidity of fluorescently labeled planar supported lipid bilayers on ozone plasma treated glass. The lipid membrane compositions examined were; DOPC, DOPC/DOPS (80/20 mol/mol) […]

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Transition Path from Two Apposed Membranes to a Stalk Obtained by a Combination of Particle Simulations and String Method

Marcus Müller, Yuliya G. Smirnova, Giovanni Marelli, Marc Fuhrmans, and An-Chang Shi

Phys. Rev. Lett. 108, 228103 (2012)

The formation of an hourglass-shaped passage (stalk) connecting two apposed membranes is an essential initial step in membrane fusion. The most probable transition path from two separate membranes to a stalk, i.e., the minimum free-energy path (MFEP), is […]

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Line-Tension Controlled Mechanism for Influenza Fusion

Herre Jelger Risselada, Giovanni Marelli, Marc Fuhrmans, Yuliya G. Smirnova, Helmut Grubmüller, Siewert Jan Marrink, Marcus Müller

PLoS ONE 7(6): e38302 (2012)

Our molecular simulations reveal that wild-type influenza fusion peptides are able to stabilize a highly fusogenic pre-fusion structure, i.e. a peptide bundle formed by four or more trans-membrane arranged fusion peptides. We rationalize that the […]

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Homo-polymers with balanced hydrophobicity translocate through lipid bilayers and enhance local solvent permeability

Marco Werner, Jens-Uwe Sommer and Vladimir A. Baulin

Soft Matter, 8, 11708-11716 (2012)

Recent experimental studies indicate that polymeric structures with a well-adjusted balance of amphiphilic parts may translocate through self-assembled phospholipid bilayers and enhance the passive trans-membrane transport of smaller molecules. Using a coarse grained lattice Monte Carlo model with explicit solvent we investigate self-assembled lipid […]

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Natural Bactericidal Surfaces: Mechanical Rupture of Pseudomonas aeruginosa Cells by Cicada Wings

Elena P. Ivanova, Jafar Hasan, Hayden K. Webb, Vi Khanh Truong, Gregory S. Watson, Jolanta A. Watson, Vladimir A. Baulin, Sergey Pogodin, James Y. Wang, Mark J. Tobin, Christian Löbbe, Russell J. Crawford

Small, 8 (16), 2489 – 2494 (2012)

Natural superhydrophobic surfaces are often thought to have antibiofouling potential due to their self-cleaning properties. However, when […]

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Permeability of lipid bilayers induced by polymers

Lipid bilayers emerge by self-organization of amphiphilic molecules and are the essential component of membranes of living cells. An important task of them is the selective exchange of substances between the cell and its environment. This becomes particularly interesting for delivering foreign molecules and RNA into the cell. In the classical view of cell biology […]

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Polymer micelles as drug carriers

Block copolymer micelles are composed of polymer chains with sequences of hydrophilic and hydrophobic blocks. In a dilute aqueous solution, they form spherical or cylindrical nano-objects comprised of several chains with a hydrophobic core and extended hydrophilic corona. Lipophilic drugs can be dissolved in the core of these micelles, while the corona will assure solubility […]

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Self-assembly of spherical interpolyelectrolyte complexes from oppositely charged polymers

V. A. Baulin and E. Trizac
Soft Matter, 8 (25), 6755 – 6766 (2012)
The formation of inter-polyelectrolyte complexes from the association of oppositely charged polymers in an electrolyte is studied. The charged polymers are linear oppositely charged polyelectrolytes, with possibly a neutral block. This leads to complexes with a charged core, and a more dilute corona […]

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Critical adsorption controls translocation of polymer chain through lipid bilayers and permeation of solvent

J.-U. Sommer, M. Werner and V. A. Baulin

Europhysics Letters, 98, 18003 (2012)

Monte Carlo simulations using an explicit solvent model indicate a new pathway for translocation of a polymer chain through a lipid bilayer. We consider a polymer chain composed of repeat units with a given hydrophobicity and a coarse-grained model of a lipid bilayer in […]

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Degradation versus self-assembly of block copolymer micelles

A. Muratov and V. A. Baulin

Langmuir, 28, 3071-3076 (2012)

The stability of micelles self-assembled from block co-polymers can be altered by the degradation of the blocks. Slow degradation shifts the equilibrium size distribution of block co-polymer micelles and changes their properties. The quasi-equilibrium scaling theory shows that the degradation of hydrophobic blocks in the core of […]

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Biomolecule Surface Patterning May Enhance Membrane Association

S. Pogodin, N. K. H. Slater and V. A. Baulin

ACS Nano, 6(2), 1308-1313 (2012)

Under dehydration conditions, amphipathic late embryogenesis abundant proteins fold spontaneously from a random conformation into α-helical structures, and this transition is promoted by the presence of membranes. To gain insight into the thermodynamics of membrane association, we model the resulting α-helical structures […]

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Anti-bacterial surfaces inspired by cicada and dragonfly wings

Many surfaces found in nature possess sophisticated topographical structures which provide them with exceptional properties. Nano-structured surface of lotus leafs efficiently repel water, microscopic brushes of gecko fingers drastically increase the contact with surfaces, topographical structures provides for enhanced anti-reflection surface properties in insects. Self-cleaning ability of bio-surfaces enables them to prevent contamination by particles […]

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Cyclodextrins and their applications

Cyclodextrins can complexate with polymers and thus can be grafted to surfaces. Grafted layers of sliding polymers are constructed from polymers threading through ring-like molecules grafted to a surface. Such grafting mode allows the polymer chains to freely slide inside the ring-like molecules, thus providing additional degree of freedom for grafted polymers.
A cyclic molecule of a cyclodextrin consist […]

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Translocation of nanoparticles, carbon nanotubes and polymers through bilayers

Cell membranes represent a serious protective barrier for external molecules, proteins, nanoparticles and drugs. This barrier is quite efficient in protecting the interior of the cells. However, large nanoscale objects, single-walled carbon nanotubes (SWNTs) have been found inside the cells both in direct and indirect biological experiments. Such experiments suggest that carbon nanotubes can efficiently […]

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Differential attraction and repulsion of Staphylococcus aureus and Pseudomonas aeruginosa on molecularly smooth titanium films

E. Ivanova, V. Khanh Truong , H. Webb , V.A. Baulin, J. Wang , N. Mohammodi, F. Wang, C. Fluke, R. Crawford

Langmuir, 27(18), 11710-11721 (2011)

Magnetron sputtering techniques were used to prepare molecularly smooth titanium thin films possessing an average roughness between 0.18 nm and 0.52 nm over 5 μm × 5 μm AFM scanning areas. Films […]

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Coupled concentration polarization and electroosmotic circulation near micro/nanointerfaces: Taylor–Aris model of hydrodynamic dispersion and limits of its applicability

A. Yaroshchuk, E. Zholkovskiy, S. Pogodin and V.A. Baulin
Langmuir, 27(18), 11710-11721 (2011)

Mismatches in electrokinetic properties between micro- and nanochannels give rise to superposition of electroosmotic and pressure-driven flows in the microchannels. Parabolic or similar flow profiles are known to cause the so-called hydrodynamic dispersion, which under certain conditions can be formally assimilated to an […]

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Equilibrium insertion of nanoscale objects into phospholipid bilayers

S. Pogodin and V.A. Baulin
Current Nanoscience, 7 (5), 721-726 (2011)

Certain membrane proteins, peptides, nanoparticles and nanotubes have rigid structure and fixed shape. They are often viewed as spheres and cylinders with certain surface properties. Single Chain Mean Field theory is used to model the equilibrium insertion of nanoscale spheres and rods into the phospholipid bilayer. […]

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Accurate critical micelle concentrations from a single chain mean field theory

A. Gezae Daful, V.A. Baulin, J. Bonet i Avalos and A.D. Mackie
J. Phys. Chem. B, 115, 3434–3443 (2011)
A single chain mean field theory is used to quantitatively describe the micellization process of the nonionic polyethylene oxide alkyl ether, CnEm class of surfactants at 25 °C. An explicit but simple microscopic model with only three […]

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Surface patterning of carbon nanotubes can enhance their penetration through a phospholipid bilayer

S. Pogodin, N.K.H. Slater and V.A. Baulin
ACS Nano, 5 (2), 1141–1146 (2011)

Nanotube patterning may occur naturally upon the spontaneous self-assembly of biomolecules onto the surface of single-walled carbon nanotubes (SWNTs). It results in periodically alternating bands of surface properties, ranging from relatively hydrophilic to hydrophobic, along the axis of the nanotube. Single-chain mean field (SCMF) […]

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Aggregation of amphiphilic polymers in the presence of adhesive small colloidal particles

V.A. Baulin, A. Johner and J. Bonet Avalos
J. Chem. Phys., 133, 174905 (2010)
The interaction of amphiphilic polymers with small colloids, capable to reversibly stick onto the chains, is studied. Adhesive small colloids in solution are able to dynamically bind two polymer segments. This association leads to topological changes in the polymer network configurations, such as […]

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Coarse-grained models of phospholipid membranes within the single chain mean field theory

S. Pogodin and V.A. Baulin
Soft Matter, 6, 2216 – 2226 (2010)
The single chain mean field theory is used to simulate the equilibrium structure of phospholipid membranes at the molecular level. Three levels of coarse-graining of DMPC phospholipid surfactants are present: the detailed 44-beads double tails model, the 10-beads double tails model and the minimal 3-beads […]

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Can a carbon nanotube pierce through a phospholipid bilayer?

S. Pogodin and V.A. Baulin
ACS Nano, 4 (9), 5293–5300 (2010)
Great efficiency to penetrate into living cells is attributed to carbon nanotubes due to a number of direct and indirect observations of carbon nanotubes inside the cells. However, a direct evidence of physical translocation of nanotubes through phospholipid bilayers and the exact microscopic mechanism of their […]

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Collision induced spatial organization of microtubules

V.A. Baulin, C.M. Marques, F. Thalmann
Biophysical Chemistry, 128(2-3), 231 – 244 (2007)
The dynamic behavior of microtubules in solution can be strongly modified by interactions with walls or other structures. We examine here a microtubule growth model where the increase in size of the plus-end is perturbed by collisions with other microtubules. We show that […]

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Micellization of Sliding Polymer Surfactants

V.A. Baulin, N.-K. Lee, A. Johner, C.M. Marques
Macromolecules, 39(2), 871 – 876 (2006)
Following up a recent paper on grafted sliding polymer layers [Macromolecules 2005, 38, 1434−1441], we investigated the influence of the sliding degree of freedom on the self-assembly of sliding polymeric surfactants that can be obtained by complexation of polymers with cyclodextrins. In contrast […]

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Sliding grafted polymer layers

V.A. Baulin, A. Johner, C.M. Marques
Macromolecules, 38(4), 1434 – 1441 (2005)
We study theoretically the structure of sliding grafted polymer layers, or SGP layers. These interfacial structures are built by attaching each polymer to the substrate with a ringlike molecule such as cyclodextrins. Such a topological grafting mode allows the chains to freely slide along the […]

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Self-assembled aggregates in the gravitational field: Growth and nematic order

V. A. Baulin
J. Chem. Phys., 119, 2874 (2003)
The influence of the gravitational field on the reversible process of assembly and disassembly of linear aggregates is the focus of this paper. Even the earth gravitational field can affect the equilibrium properties of heavy biological aggregates such as microtubules or actin filaments. The gravity gives rise to […]

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Self-consistent field theory of brushes of neutral water-soluble polymers

V.A. Baulin, E.B. Zhulina, A. Halperin
J. Chem. Phys., 119, 2874 (2003)
The self-consistent field theory of brushes of neutral water-soluble polymers described by two-state models is formulated in terms of the effective Flory interaction parameter χeff(T,ϕ) that depends on both temperature, T, and the monomer volume fraction, ϕ. The concentration profiles, distribution of free ends and […]

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Signatures of a concentration dependent Flory chi parameter: swelling and collapse of coils and brushes

V. A. Baulin and A. Halperin
Macromolecules, 35, 6432 – 6438 (2002)
The quality of solvents of polymers is often described in terms of the Flory χ parameter typically assumed to depend only on the temperature, T. In certain polymer-solvent systems fitting the experimental data enforces the replacement of (χT) by a concentration-dependent χeff. In turn, this modifies […]

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