Colloids and Surfaces A: Physicochemical and Engineering Aspects, Aug 1, 2021
Abstract We have studied the properties of multicontinuous structures with cubic symmetry. They a... more Abstract We have studied the properties of multicontinuous structures with cubic symmetry. They are formed in many different systems such as diblock copolymers, lipid and surfactant mixtures. We have obtained new multicontinuous structures with different topology of two intertwined networks of channels within the framework of the Landau-Brazovskii functional with one scalar order parameter. We have analyzed the stability and classified different types of multicontinuous structures based on the topology and number of distinct continuous layers within the structure.
Journal of Physics: Condensed Matter, Aug 22, 2016
We have developed a theory for inhomogeneous systems that allows for incorporation of effects of ... more We have developed a theory for inhomogeneous systems that allows for incorporation of effects of mesoscopic fluctuations. A hierarchy of equations relating the correlation and direct correlation functions for the local excess φ(r) of the volume fraction of particles ζ has been obtained, and an approximation leading to a closed set of equations for the two-point functions has been introduced for the disordered inhomogeneous phase. We have solved numerically the self-consistent equations for one (1D) and three (3D) dimensional models with short-range attraction and long-rannge repulsion (SALR). Predictions for all the qualitative properties of the 1D model agree with the exact results, but only semi-quantitative agreement is obtained in the simplest version of the theory. The effects of fluctuations in the two considered 3D models are significantly different, despite very similar properties of these models in the mean-field approximation. In both cases we obtain the sequence of large-small-large compressibility for increasing ζ. The very small compressibility is accompanied by the oscillatory decay of correlations with the correlation length orders of magnitude larger than the size of particles. Only in one of the two considered models for decreasing temperature the small compressibility becomes very small and the large compressibility becomes very large, and eventually van der Waals loops appear. Further studies are necessary to determine the nature of the strongly inhomogeneous phase present for intermediate volume fractions in 3D.
Journal of Physics: Condensed Matter, Apr 26, 2016
We study effects of fluctuations on the mesoscopic length-scale on systems with mesoscopic inhomo... more We study effects of fluctuations on the mesoscopic length-scale on systems with mesoscopic inhomogeneities. Equations for the correlation function and for the average volume fraction are derived in the self-consistent Gaussian approximation. The equations are further simplified by postulating the expression for the structure factor consistent with scattering experiments for self-assembling systems. Predictions of the approximate theory are verified by a comparison with the exact results obtained earlier for the one-dimensional lattice model with first-neighbour attraction and thirdneighbour repulsion. We find qualitative agreement for the correlation function, the equation of state and the dependence of the chemical potential µ on the volume fraction ζ. Our results confirm also that strong inhomogeneities in the disordered phase are found only in the case of strong repulsion. The inhomogeneities are reflected in an oscillatory decay of the correlation function with a very large correlation length, three inflection points in the µ(ζ) curve and a compressibility that for increasing ζ takes very large, very small and again very large values.
Mechanical adaptions of cells, including stiffness variation, cytoskeleton remodeling, motion coo... more Mechanical adaptions of cells, including stiffness variation, cytoskeleton remodeling, motion coordination, and shape changing, are essential for tissue morphogenesis, wound healing, and malignant progression. In this paper, we take confluent monolayers of Madin-Darby canine kidney (MDCK) and mouse myoblast (C2C12) cells as model systems to probe how cells collectively adapt their mechanical features in response to a free tissue boundary. We show that the free boundary not only can trigger unjamming transition but also induces cell fluidization nearby the boundary. The Young's moduli of cells near the boundary are found to be much lower than those of interior cells. We demonstrate that the stiffness of cells in monolayers with a free tissue boundary exhibits negative dependence on the projected cell area, in contrast to previous studies where cells were found to stiffen as cellular area increases in a confluent MDCK monolayer without boundary. In addition, the free tissue boundary may activate cell remodeling, rendering volume enlargement and cell-specified cytoskeleton organization. Our study emphasizes the important role of geometrical boundary in regulating biomechanical properties of cell aggregates.
The shape transformations of lipid vesicles induced by the adhesion to a flat surface is investig... more The shape transformations of lipid vesicles induced by the adhesion to a flat surface is investigated. We perform the calculations within the framework of the Helfrich spontaneous curvature model. The calculations were performed for a few values of the reduced volume and the spontaneous curvature. The range of stability for different shapes (oblate, prolate, and stomatocyte) of adhered vesicles is determined. New physical phenomena such as budding induced by the adhesion of vesicles are reported.
Chiral active matter capable of self-rotation can form skyrmions, which spontaneously organize in... more Chiral active matter capable of self-rotation can form skyrmions, which spontaneously organize into lattices or undergo dynamic phase separation, dependent on the competition between the chiral and polar coherence length scales.
However, the actual broad range of v for which stable disk-like RBC shapes exist cannot be reprod... more However, the actual broad range of v for which stable disk-like RBC shapes exist cannot be reproduced using the existing theoretical approaches 4,7,12-15. Recent investigations 16,17 suggest that several key features of biological systems are dominated by geometry. Minimal models, which are capable of reproducing a rich variety of existing membrane structures, typically treat them as fluid structureless 2D curved thin films. A pioneering mesoscopic model was introduced by Helfrich 4,12 , where the variational parameter is the membrane curvature tensor C , represented by its invariants, namely, the Gaussian curvature K and the mean curvature H. The Helfrich model predicts three qualitatively different RBC shapes upon varying of the reduced volume v: (i) stomatocytes (Fig. 1a), (ii) oblate discocytes (Fig. 1b) and (iii) prolate shapes (Fig. 1d). These shapes are stable in different regimes of v values: (i)v < v 1 , (ii) ≤ ≤ v v v 1 2 , (iii) v > v 2 , where v 1 ~ 0.59 and v 2 ~ 0.65. Therefore, the window [v 1 , v 2 ] of stable discocyte shapes is relatively narrow with respect to experimental observations.
We have calculated the values of the critical packing fractions for the mixtures of symmetric non... more We have calculated the values of the critical packing fractions for the mixtures of symmetric nonadditive hard spheres at high densities for small values of the nonadditivity parameter. Calculations have been performed for solid−solid and fluid−fluid demixing transitions. A cluster algorithm for Monte Carlo simulations in a semigrand ensemble was used, and the waste recycling method was applied to improve the accuracy of the calculations. The finite size scaling analysis was employed to compute the critical packing fractions for infinite systems with high accuracy.
A mesoscopic theory for the primitive model of ionic systems is developed for arbitrary size, λ =... more A mesoscopic theory for the primitive model of ionic systems is developed for arbitrary size, λ = σ + /σ − , and charge, Z = e + /|e − |, asymmetry. Our theory is an extension of the theory we developed earlier for the restricted primitive model. The case of extreme asymmetries λ → ∞ and Z → ∞ is studied in some detail in a mean-field approximation. The phase diagram and correlation functions are obtained in the asymptotic regime λ → ∞ and Z → ∞, and for infinite dilution of the larger ions (volume fraction n p ∼ 1/Z or less). We find a coexistence between a very dilute 'gas' phase and a crystalline phase in which the macroions form a bcc structure with the lattice constant ≈ 3.6σ +. Such coexistence was observed experimentally in deionized aqueous solutions of highly charged colloidal particles.
The primitive model of ionic systems is investigated within a field-theoretic description for the... more The primitive model of ionic systems is investigated within a field-theoretic description for the whole range of size-, λ, and charge, Z, ratios of the two ionic species. Two order parameters (OP) are identified, and their relations to physically relevant quantities are described for various values of λ and Z. Instabilities of the disordered phase associated with the two OP's are determined in the mean-field approximation (MF). In MF a gas-liquid separation occurs for any Z and λ = 1. In addition, an instability with respect to various types of periodic ordering of the two kinds of ions is found. Depending on λ and Z, one or the other transition is metastable in different thermdynamic states. The instabilities found in MF represent weak ordering of the majority of the instantaneous states, and are identified with structural loci associated with pretransitional effects.
We present the formation of oriented thin lipid films belonging to the primitive () bicontinuous ... more We present the formation of oriented thin lipid films belonging to the primitive () bicontinuous cubic phase, as characterized by grazing-incidence small angle X-ray scattering and atomic force microscopy. The phase shows high out-of-plane orientation with the (100) plane parallel to the substrate; this is consistent across a number of different lipid and surfactant systems. We demonstrate that the adopted orientation can be predicted using a theoretical framework, based on the most favorable facet in terms of curvature energy whilst assuming a closed bilayer. Significantly, the Primitive bicontinuous cubic phase is unique in that it contains straight water channels, with the [100] orientation presenting a square array at the surface with the straight channels running directly parallel and perpendicular to the interface. Moreover, by tuning the composition we show that we can tune the periodic pore-to-pore spacing (lattice parameter) of the structure with control over nanostructure dimensions. We present structures with lattice parameters between 13 and 23 nm. These structural features are important for applications including delivery of bioactive agents, and patterning and templating of inorganic nanomaterials. These findings represent a route to square arrays of nanofeatures with 2-3 times smaller periodicity (4-9 times higher per-area density) than those reported from block copolymer lithographic template systems.
Collective cell migration is extensively observed in embryo development and cancer invasion. Duri... more Collective cell migration is extensively observed in embryo development and cancer invasion. During these processes, the interactions between cells with distinct identities and fates are of importance for boundary formation and host defense against cancer. In this paper, we explore the collective dynamics of a two-dimensional cell mixing monolayer consisting of non-tumorigenic mammary epithelial cells and breast cancer cells. We show that the epithelial–cancerous cell mixing system displays unique sorting behaviors. The epithelial cells aggregate to form scattered clusters, which perform random motion with simultaneous translation and rotation, strikingly distinct from the classical persistent random walk of individual migratory cells. The motility of cancer cells is markedly promoted by the epithelial clusters, exhibiting remarkable contact enhancement of locomotion. A discrete model based on the Johnson–Kendall–Roberts contact mechanics is proposed to identify the influence of intercellular interactions, active migration forces and cell–substrate friction forces on the collective cell dynamics. These findings could advance our understanding of many biological processes, such as cancer metastasis and tissue morphogenesis. The epithelial–cancerous cell mixing system displays unique collective dynamics. The epithelial cells aggregate to form scattered clusters, which perform random motion with simultaneous translation and rotation, strikingly distinct from the classical persistent random walk of individual migratory cells. The interactions between the two cell types drive the evolution of collective migration dynamics and give rise to a behavior akin to the contact enhancement of locomotion. This study revealed the distinctive dynamic features and the underlying regulatory mechanisms arising from epithelial–cancerous interactions.
Systems with short-range attraction and long-range repulsion can form ordered microphases in bulk... more Systems with short-range attraction and long-range repulsion can form ordered microphases in bulk and under confinement. Using grand canonical Monte Carlo simulations, we study a colloidal system with competing interactions under confinement in narrow spherical shells at thermodynamic conditions at which the hexagonal phase of cylindrical clusters is stable in bulk. We observe spontaneous formation of different ordered structures. The results of the simulations are in a very good agreement with the predictions of a simple mathematical model based on the geometry and optimal packing of colloidal clusters. The results of the simulations and the explanation provided by a relatively simple geometric model may be helpful in manufacturing copolymer nanocapsules and may indicate possible ways of coiling DNA strands on spherical objects.
Self-assembled structures in cylinder-forming systems with competing interactions confined in nar... more Self-assembled structures in cylinder-forming systems with competing interactions confined in narrow spherical shells.
In this review paper, we theoretically explain the origin of electrostatic interactions between l... more In this review paper, we theoretically explain the origin of electrostatic interactions between lipid bilayers and charged solid surfaces using a statistical mechanics approach, where the orientational degree of freedom of lipid head groups and the orientational ordering of the water dipoles are considered. Within the modified Langevin Poisson–Boltzmann model of an electric double layer, we derived an analytical expression for the osmotic pressure between the planar zwitterionic lipid bilayer and charged solid planar surface. We also show that the electrostatic interaction between the zwitterionic lipid head groups of the proximal leaflet and the negatively charged solid surface is accompanied with a more perpendicular average orientation of the lipid head-groups. We further highlight the important role of the surfaces’ nanostructured topography in their interactions with biological material. As an example of nanostructured surfaces, we describe the synthesis of TiO2 nanotubular and...
Simulations show that periodic modulated phases formed from colloidal particles with competing in... more Simulations show that periodic modulated phases formed from colloidal particles with competing interactions become internally ordered at low temperature.
In this work, we explore the possibility of promoting the formation of ordered microphases by con... more In this work, we explore the possibility of promoting the formation of ordered microphases by confinement of colloids with competing interactions in ordered porous materials. For that aim, we consider three families of porous materials modeled as cubic primitive, diamond, and gyroid bicontinuous phases. The structure of the confined colloids is investigated by means of grand canonical Monte Carlo simulations in thermodynamic conditions at which either a cluster crystal or a cylindrical phase is stable in bulk. We find that by tuning the size of the unit cell of these porous materials, numerous novel ordered microphases can be produced, including cluster crystals arranged into close packed and open lattices as well as nonparallel cylindrical phases.
The adhesion of lipid vesicles to a rigid flat surface is investigated. We examine the influence ... more The adhesion of lipid vesicles to a rigid flat surface is investigated. We examine the influence of the membrane spontaneous curvature, adhesion strength, and the reduced volume on the stability and shape transformations of adhered vesicles. The minimal strength of the adhesion necessary to stabilize the shapes of adhered vesicles belonging to different shape classes is determined. It is shown that the budding of an adhered vesicle may be induced by the change of the adhesion strength. The importance of the free vesicle shape for its susceptibility to adhesion is discussed.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, Aug 1, 2021
Abstract We have studied the properties of multicontinuous structures with cubic symmetry. They a... more Abstract We have studied the properties of multicontinuous structures with cubic symmetry. They are formed in many different systems such as diblock copolymers, lipid and surfactant mixtures. We have obtained new multicontinuous structures with different topology of two intertwined networks of channels within the framework of the Landau-Brazovskii functional with one scalar order parameter. We have analyzed the stability and classified different types of multicontinuous structures based on the topology and number of distinct continuous layers within the structure.
Journal of Physics: Condensed Matter, Aug 22, 2016
We have developed a theory for inhomogeneous systems that allows for incorporation of effects of ... more We have developed a theory for inhomogeneous systems that allows for incorporation of effects of mesoscopic fluctuations. A hierarchy of equations relating the correlation and direct correlation functions for the local excess φ(r) of the volume fraction of particles ζ has been obtained, and an approximation leading to a closed set of equations for the two-point functions has been introduced for the disordered inhomogeneous phase. We have solved numerically the self-consistent equations for one (1D) and three (3D) dimensional models with short-range attraction and long-rannge repulsion (SALR). Predictions for all the qualitative properties of the 1D model agree with the exact results, but only semi-quantitative agreement is obtained in the simplest version of the theory. The effects of fluctuations in the two considered 3D models are significantly different, despite very similar properties of these models in the mean-field approximation. In both cases we obtain the sequence of large-small-large compressibility for increasing ζ. The very small compressibility is accompanied by the oscillatory decay of correlations with the correlation length orders of magnitude larger than the size of particles. Only in one of the two considered models for decreasing temperature the small compressibility becomes very small and the large compressibility becomes very large, and eventually van der Waals loops appear. Further studies are necessary to determine the nature of the strongly inhomogeneous phase present for intermediate volume fractions in 3D.
Journal of Physics: Condensed Matter, Apr 26, 2016
We study effects of fluctuations on the mesoscopic length-scale on systems with mesoscopic inhomo... more We study effects of fluctuations on the mesoscopic length-scale on systems with mesoscopic inhomogeneities. Equations for the correlation function and for the average volume fraction are derived in the self-consistent Gaussian approximation. The equations are further simplified by postulating the expression for the structure factor consistent with scattering experiments for self-assembling systems. Predictions of the approximate theory are verified by a comparison with the exact results obtained earlier for the one-dimensional lattice model with first-neighbour attraction and thirdneighbour repulsion. We find qualitative agreement for the correlation function, the equation of state and the dependence of the chemical potential µ on the volume fraction ζ. Our results confirm also that strong inhomogeneities in the disordered phase are found only in the case of strong repulsion. The inhomogeneities are reflected in an oscillatory decay of the correlation function with a very large correlation length, three inflection points in the µ(ζ) curve and a compressibility that for increasing ζ takes very large, very small and again very large values.
Mechanical adaptions of cells, including stiffness variation, cytoskeleton remodeling, motion coo... more Mechanical adaptions of cells, including stiffness variation, cytoskeleton remodeling, motion coordination, and shape changing, are essential for tissue morphogenesis, wound healing, and malignant progression. In this paper, we take confluent monolayers of Madin-Darby canine kidney (MDCK) and mouse myoblast (C2C12) cells as model systems to probe how cells collectively adapt their mechanical features in response to a free tissue boundary. We show that the free boundary not only can trigger unjamming transition but also induces cell fluidization nearby the boundary. The Young's moduli of cells near the boundary are found to be much lower than those of interior cells. We demonstrate that the stiffness of cells in monolayers with a free tissue boundary exhibits negative dependence on the projected cell area, in contrast to previous studies where cells were found to stiffen as cellular area increases in a confluent MDCK monolayer without boundary. In addition, the free tissue boundary may activate cell remodeling, rendering volume enlargement and cell-specified cytoskeleton organization. Our study emphasizes the important role of geometrical boundary in regulating biomechanical properties of cell aggregates.
The shape transformations of lipid vesicles induced by the adhesion to a flat surface is investig... more The shape transformations of lipid vesicles induced by the adhesion to a flat surface is investigated. We perform the calculations within the framework of the Helfrich spontaneous curvature model. The calculations were performed for a few values of the reduced volume and the spontaneous curvature. The range of stability for different shapes (oblate, prolate, and stomatocyte) of adhered vesicles is determined. New physical phenomena such as budding induced by the adhesion of vesicles are reported.
Chiral active matter capable of self-rotation can form skyrmions, which spontaneously organize in... more Chiral active matter capable of self-rotation can form skyrmions, which spontaneously organize into lattices or undergo dynamic phase separation, dependent on the competition between the chiral and polar coherence length scales.
However, the actual broad range of v for which stable disk-like RBC shapes exist cannot be reprod... more However, the actual broad range of v for which stable disk-like RBC shapes exist cannot be reproduced using the existing theoretical approaches 4,7,12-15. Recent investigations 16,17 suggest that several key features of biological systems are dominated by geometry. Minimal models, which are capable of reproducing a rich variety of existing membrane structures, typically treat them as fluid structureless 2D curved thin films. A pioneering mesoscopic model was introduced by Helfrich 4,12 , where the variational parameter is the membrane curvature tensor C , represented by its invariants, namely, the Gaussian curvature K and the mean curvature H. The Helfrich model predicts three qualitatively different RBC shapes upon varying of the reduced volume v: (i) stomatocytes (Fig. 1a), (ii) oblate discocytes (Fig. 1b) and (iii) prolate shapes (Fig. 1d). These shapes are stable in different regimes of v values: (i)v < v 1 , (ii) ≤ ≤ v v v 1 2 , (iii) v > v 2 , where v 1 ~ 0.59 and v 2 ~ 0.65. Therefore, the window [v 1 , v 2 ] of stable discocyte shapes is relatively narrow with respect to experimental observations.
We have calculated the values of the critical packing fractions for the mixtures of symmetric non... more We have calculated the values of the critical packing fractions for the mixtures of symmetric nonadditive hard spheres at high densities for small values of the nonadditivity parameter. Calculations have been performed for solid−solid and fluid−fluid demixing transitions. A cluster algorithm for Monte Carlo simulations in a semigrand ensemble was used, and the waste recycling method was applied to improve the accuracy of the calculations. The finite size scaling analysis was employed to compute the critical packing fractions for infinite systems with high accuracy.
A mesoscopic theory for the primitive model of ionic systems is developed for arbitrary size, λ =... more A mesoscopic theory for the primitive model of ionic systems is developed for arbitrary size, λ = σ + /σ − , and charge, Z = e + /|e − |, asymmetry. Our theory is an extension of the theory we developed earlier for the restricted primitive model. The case of extreme asymmetries λ → ∞ and Z → ∞ is studied in some detail in a mean-field approximation. The phase diagram and correlation functions are obtained in the asymptotic regime λ → ∞ and Z → ∞, and for infinite dilution of the larger ions (volume fraction n p ∼ 1/Z or less). We find a coexistence between a very dilute 'gas' phase and a crystalline phase in which the macroions form a bcc structure with the lattice constant ≈ 3.6σ +. Such coexistence was observed experimentally in deionized aqueous solutions of highly charged colloidal particles.
The primitive model of ionic systems is investigated within a field-theoretic description for the... more The primitive model of ionic systems is investigated within a field-theoretic description for the whole range of size-, λ, and charge, Z, ratios of the two ionic species. Two order parameters (OP) are identified, and their relations to physically relevant quantities are described for various values of λ and Z. Instabilities of the disordered phase associated with the two OP's are determined in the mean-field approximation (MF). In MF a gas-liquid separation occurs for any Z and λ = 1. In addition, an instability with respect to various types of periodic ordering of the two kinds of ions is found. Depending on λ and Z, one or the other transition is metastable in different thermdynamic states. The instabilities found in MF represent weak ordering of the majority of the instantaneous states, and are identified with structural loci associated with pretransitional effects.
We present the formation of oriented thin lipid films belonging to the primitive () bicontinuous ... more We present the formation of oriented thin lipid films belonging to the primitive () bicontinuous cubic phase, as characterized by grazing-incidence small angle X-ray scattering and atomic force microscopy. The phase shows high out-of-plane orientation with the (100) plane parallel to the substrate; this is consistent across a number of different lipid and surfactant systems. We demonstrate that the adopted orientation can be predicted using a theoretical framework, based on the most favorable facet in terms of curvature energy whilst assuming a closed bilayer. Significantly, the Primitive bicontinuous cubic phase is unique in that it contains straight water channels, with the [100] orientation presenting a square array at the surface with the straight channels running directly parallel and perpendicular to the interface. Moreover, by tuning the composition we show that we can tune the periodic pore-to-pore spacing (lattice parameter) of the structure with control over nanostructure dimensions. We present structures with lattice parameters between 13 and 23 nm. These structural features are important for applications including delivery of bioactive agents, and patterning and templating of inorganic nanomaterials. These findings represent a route to square arrays of nanofeatures with 2-3 times smaller periodicity (4-9 times higher per-area density) than those reported from block copolymer lithographic template systems.
Collective cell migration is extensively observed in embryo development and cancer invasion. Duri... more Collective cell migration is extensively observed in embryo development and cancer invasion. During these processes, the interactions between cells with distinct identities and fates are of importance for boundary formation and host defense against cancer. In this paper, we explore the collective dynamics of a two-dimensional cell mixing monolayer consisting of non-tumorigenic mammary epithelial cells and breast cancer cells. We show that the epithelial–cancerous cell mixing system displays unique sorting behaviors. The epithelial cells aggregate to form scattered clusters, which perform random motion with simultaneous translation and rotation, strikingly distinct from the classical persistent random walk of individual migratory cells. The motility of cancer cells is markedly promoted by the epithelial clusters, exhibiting remarkable contact enhancement of locomotion. A discrete model based on the Johnson–Kendall–Roberts contact mechanics is proposed to identify the influence of intercellular interactions, active migration forces and cell–substrate friction forces on the collective cell dynamics. These findings could advance our understanding of many biological processes, such as cancer metastasis and tissue morphogenesis. The epithelial–cancerous cell mixing system displays unique collective dynamics. The epithelial cells aggregate to form scattered clusters, which perform random motion with simultaneous translation and rotation, strikingly distinct from the classical persistent random walk of individual migratory cells. The interactions between the two cell types drive the evolution of collective migration dynamics and give rise to a behavior akin to the contact enhancement of locomotion. This study revealed the distinctive dynamic features and the underlying regulatory mechanisms arising from epithelial–cancerous interactions.
Systems with short-range attraction and long-range repulsion can form ordered microphases in bulk... more Systems with short-range attraction and long-range repulsion can form ordered microphases in bulk and under confinement. Using grand canonical Monte Carlo simulations, we study a colloidal system with competing interactions under confinement in narrow spherical shells at thermodynamic conditions at which the hexagonal phase of cylindrical clusters is stable in bulk. We observe spontaneous formation of different ordered structures. The results of the simulations are in a very good agreement with the predictions of a simple mathematical model based on the geometry and optimal packing of colloidal clusters. The results of the simulations and the explanation provided by a relatively simple geometric model may be helpful in manufacturing copolymer nanocapsules and may indicate possible ways of coiling DNA strands on spherical objects.
Self-assembled structures in cylinder-forming systems with competing interactions confined in nar... more Self-assembled structures in cylinder-forming systems with competing interactions confined in narrow spherical shells.
In this review paper, we theoretically explain the origin of electrostatic interactions between l... more In this review paper, we theoretically explain the origin of electrostatic interactions between lipid bilayers and charged solid surfaces using a statistical mechanics approach, where the orientational degree of freedom of lipid head groups and the orientational ordering of the water dipoles are considered. Within the modified Langevin Poisson–Boltzmann model of an electric double layer, we derived an analytical expression for the osmotic pressure between the planar zwitterionic lipid bilayer and charged solid planar surface. We also show that the electrostatic interaction between the zwitterionic lipid head groups of the proximal leaflet and the negatively charged solid surface is accompanied with a more perpendicular average orientation of the lipid head-groups. We further highlight the important role of the surfaces’ nanostructured topography in their interactions with biological material. As an example of nanostructured surfaces, we describe the synthesis of TiO2 nanotubular and...
Simulations show that periodic modulated phases formed from colloidal particles with competing in... more Simulations show that periodic modulated phases formed from colloidal particles with competing interactions become internally ordered at low temperature.
In this work, we explore the possibility of promoting the formation of ordered microphases by con... more In this work, we explore the possibility of promoting the formation of ordered microphases by confinement of colloids with competing interactions in ordered porous materials. For that aim, we consider three families of porous materials modeled as cubic primitive, diamond, and gyroid bicontinuous phases. The structure of the confined colloids is investigated by means of grand canonical Monte Carlo simulations in thermodynamic conditions at which either a cluster crystal or a cylindrical phase is stable in bulk. We find that by tuning the size of the unit cell of these porous materials, numerous novel ordered microphases can be produced, including cluster crystals arranged into close packed and open lattices as well as nonparallel cylindrical phases.
The adhesion of lipid vesicles to a rigid flat surface is investigated. We examine the influence ... more The adhesion of lipid vesicles to a rigid flat surface is investigated. We examine the influence of the membrane spontaneous curvature, adhesion strength, and the reduced volume on the stability and shape transformations of adhered vesicles. The minimal strength of the adhesion necessary to stabilize the shapes of adhered vesicles belonging to different shape classes is determined. It is shown that the budding of an adhered vesicle may be induced by the change of the adhesion strength. The importance of the free vesicle shape for its susceptibility to adhesion is discussed.
Uploads
Papers by Wojciech Gozdz