Attraction between negatively charged surfaces mediated by spherical counterions with quadrupolar charge distribution
08 Sep 2008-Journal of Chemical Physics (American Institute of Physics)-Vol. 129, Iss: 10, pp 105101-105101
TL;DR: For high enough charge densities of the interacting surfaces and large enough l, the interaction between surfaces turns repulsive as the distance between charges is reduced, and within a mean field approach an attractive interaction between like-charged surfaces originating from orientational ordering of quadrupolar counterions is obtained.
Abstract: We observed monoclonal antibody mediated coalescence of negatively charged giant unilamellar phospholipid vesicles upon close approach of the vesicles. This feature is described, using a mean field density functional theory and Monte Carlo simulations, as that of two interacting flat electrical double layers. Antibodies are considered as spherical counterions of finite dimensions with two equal effective charges spatially separated by a fixed distance l inside it. We calculate the equilibrium configuration of the system by minimizing the free energy. The results obtained by solving the integrodifferential equation and by performing the Monte Carlo simulation are in excellent agreement. For high enough charge densities of the interacting surfaces and large enough l, we obtain within a mean field approach an attractive interaction between like-charged surfaces originating from orientational ordering of quadrupolar counterions. As expected, the interaction between surfaces turns repulsive as the distance between charges is reduced.
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TL;DR: Perhaps the most spectacular and surprising one-dimensional structures and their unique biomedical applications for increased osseointegration, protein interaction and antibacterial properties are focused on.
Abstract: Titanium and titanium alloys exhibit a unique combination of strength and biocompatibility, which enables their use in medical applications and accounts for their extensive use as implant materials in the last 50 years. Currently, a large amount of research is being carried out in order to determine the optimal surface topography for use in bioapplications, and thus the emphasis is on nanotechnology for biomedical applications. It was recently shown that titanium implants with rough surface topography and free energy increase osteoblast adhesion, maturation and subsequent bone formation. Furthermore, the adhesion of different cell lines to the surface of titanium implants is influenced by the surface characteristics of titanium; namely topography, charge distribution and chemistry. The present review article focuses on the specific nanotopography of titanium, i.e. titanium dioxide (TiO2) nanotubes, using a simple electrochemical anodisation method of the metallic substrate and other processes such as the hydrothermal or sol-gel template. One key advantage of using TiO2 nanotubes in cell interactions is based on the fact that TiO2 nanotube morphology is correlated with cell adhesion, spreading, growth and differentiation of mesenchymal stem cells, which were shown to be maximally induced on smaller diameter nanotubes (15 nm), but hindered on larger diameter (100 nm) tubes, leading to cell death and apoptosis. Research has supported the significance of nanotopography (TiO2 nanotube diameter) in cell adhesion and cell growth, and suggests that the mechanics of focal adhesion formation are similar among different cell types. As such, the present review will focus on perhaps the most spectacular and surprising one-dimensional structures and their unique biomedical applications for increased osseointegration, protein interaction and antibacterial properties.
395 citations
TL;DR: It is suggested that osteoblasts are most strongly bound along the sharp convex edges or spikes of nanorough titanium surfaces where the magnitude of the negative surface charge density is the highest and it is plausible that nanorough regions of titanium surfaces with sharp edges and spikes promote the adhesion of osteoblast.
Abstract: This work considers the adhesion of cells to a nanorough titanium implant surface with sharp edges. The basic assumption was that the attraction between the negatively charged titanium surface and a negatively charged osteoblast is mediated by charged proteins with a distinctive quadrupolar internal charge distribution. Similarly, cation-mediated attraction between fibronectin molecules and the titanium surface is expected to be more efficient for a high surface charge density, resulting in facilitated integrin mediated osteoblast adhesion. We suggest that osteoblasts are most strongly bound along the sharp convex edges or spikes of nanorough titanium surfaces where the magnitude of the negative surface charge density is the highest. It is therefore plausible that nanorough regions of titanium surfaces with sharp edges and spikes promote the adhesion of osteoblasts.
168 citations
Cites background from "Attraction between negatively charg..."
...The origin of attractive interactions between two negatively charged surfaces lies in the electrostatic attraction between the positively charged domains on the tips of the titanium surface-bound proteins and the negative charges of the opposite osteoblast membrane (Figure 2B).(15,27) 15 nm...
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...The corresponding attractive force is also called the bridging force.(15,27) The origin of attractive interactions between two negatively charged surfaces lies in the electrostatic attraction between the positively charged domains on the tips of the titanium surface-bound proteins and the negative charges of the opposite osteoblast membrane (Figure 2B)....
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...A typical example of such a bridging protein with positively charged tips is β 2-GPI protein which may induce strong attraction between negatively charged surfaces.(27,28) In accordance with the above suggested mechanism of protein-mediated interaction between negatively charged osteoblasts and a negatively charged titanium surface, many studies in the past indicated that increased negative surface potential of the titanium implant promotes osteoblast adhesion and consequently new bone formation....
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...Note that a nonzero quadrupolar internal charge distribution of the protein does not exclude the possibility that the protein carries net zero or negative total charge (see also).(27,28) In order to assess the influence of geometrically structured titanium profiles on the surface charge density and electric field at the implant surface, we concentrated on estimation of the electric field at their most convex part....
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TL;DR: The influence of a finite volume of ions and orientational ordering of water Langevin dipoles on the dielectric permittivity profile in the vicinity of charged surface is studied theoretically via a numerical solution of the modified Poisson-Boltzmann equation.
73 citations
TL;DR: It is suggested that the synergy between these two processes is responsible for successful osteointegration along the titanium surface implant.
Abstract: Due to oxidation and adsorption of chloride and hydroxyl anions, the surface of titanium (Ti) implants is negatively charged. A possible mechanism of the attractive interaction between the negatively charged Ti surface and the negatively charged osteoblasts is described theoretically. It is shown that adhesion of positively charged proteins with internal charge distribution may give rise to attractive interaction between the Ti surface and the osteoblast membrane. A dynamic model of the osteoblast attachment is presented in order to study the impact of geometrically structured Ti surfaces on the osteoblasts attachment. It is indicated that membrane-bound protein complexes (PCs) may increase the membrane protrusion growth between the osteoblast and the grooves on titanium (Ti) surface and thereby facilitate the adhesion of osteoblasts to the Ti surface. On the other hand, strong local adhesion due to electrostatic forces may locally trap the osteoblast membrane and hinder the further spreading of osteointe...
72 citations
Cites methods from "Attraction between negatively charg..."
...The hard-core interactions between the proteins and the charged surfaces of implant are taken into account by means of the distance of the closest approach (Urbanija et al. 2008; Perutkova, Frank et al. 2010)....
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TL;DR: It is demonstrated that nontrivial interactions between steric effect and electrical-double-layer (EDL) overlap phenomena may augment the effective extent of EDL overlap in narrow fluidic confinements to a significant extent by virtue of rendering the channel centerline potential tending to the ζ potential in a limiting sense as the stericEffect progressively intensifies.
Abstract: In this paper, we demonstrate that nontrivial interactions between steric effect and electrical-double-layer (EDL) overlap phenomena may augment the effective extent of EDL overlap in narrow fluidic confinements to a significant extent by virtue of rendering the channel centerline potential tending to the ζ potential in a limiting sense as the steric effect progressively intensifies. Such a behavior may result in a virtually uniform (undiminished) magnitude of the EDL potential across the entire channel height and may cause lowering of the total charge within the EDL.
66 citations
References
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TL;DR: The ternary system NaA (AOT)-CaA2-SH2O (A = di-2-ethylhexylsulfosuccinate) has been studied through SH and STNa NMR measurements.
Abstract: The ternary system NaA (AOT)-CaA2-SH2O (A = di-2-ethylhexylsulfosuccinate) has been studied through SH and STNa NMR measurements. The phase diagram at 300 K has been determined and the SH and STNa quadrupolar splittings are measured for the lamellar liquid-crystalline phase. It is shown that the thermodynamic properties of the phase equilibria combined with the molecular information obtained from the NMR spectra provide crucial information on electrostatic interactions in the system. The experimental observations are interpreted in light of recent theoretical work on double-layer and hydration forces in lamellar liquid-crystalline systems. Very good agreement between theory and experiment is found. In particular it is demonstrated that (I) two lamellar liquid-crystalline phases coexist, (ii) attractive double-layer forces appear at high CaA2 content, and (iii) CaS ions are repelled by the lamellar surface at short distances supporting the suggestion that image changes are responsible for the swelling of the lamellar liquid-crystalline phase at low water content. 35 references, 6 figures, 1 table.
97 citations
TL;DR: This work demonstrates that Poisson-Boltzmann theory is able to predict attractive interactions if the spatially extended structure (which reflects the presence of intramolecular correlations) of the mobile ions in the electrolyte is accounted for, and demonstrates this for the case of divalent, mobile ions.
Abstract: Like-charged macroions in aqueous electrolyte solution can attract each other because of the presence of inter- and/or intramolecular correlations. Poisson-Boltzmann theory is able to predict attractive interactions if the spatially extended structure (which reflects the presence of intramolecular correlations) of the mobile ions in the electrolyte is accounted for. We demonstrate this for the case of divalent, mobile ions where each ion consists of two individual charges separated by a fixed distance. Variational theory applied to this symmetric 2:2 electrolyte of rodlike ions leads to an integro-differential equation, valid for arbitrary rod length. Numerical solutions reveal the existence of a critical rod length above which electrostatic attraction starts to emerge. This electrostatic attraction is distinct from nonelectrostatic depletion forces. Analysis of the orientational distribution functions suggests a bridging mechanism of the rodlike ions to hold the two macroions together. For sufficiently large rod length, we also observe "overcharging", that is, an over-compensation of the macroion charges by the diffuse layer of mobile rodlike ions. Our results emphasize the importance of the often rodlike internal structure that condensing agents such as polyamines, peptides, or polymer segments exhibit. The results were compared with Monte Carlo simulations.
77 citations
TL;DR: In this article, the authors apply mean-field level Poisson Boltzmann (PB) theory to the generic case of divalent rod-like salt ions and find attraction between like-charged macroions above a critical distance between the two individual charges of the rodlike ions.
Abstract: Attractive interactions between identical like-charged macroions in aqueous multivalent salt solution arise due to ion-ion correlations. The mean-field level Poisson-Boltzmann (PB) theory does not predict such behavior for point-like structureless ions. Various multivalent ions, such as certain DNA condensing agents or short stiff polyelectrolytes, do have an internal, often rod-like, structure. Applying PB theory to the generic case of divalent rod-like salt ions, we find attraction between like-charged macroions above a critical distance between the two individual charges of the rod-like ions. We calculate this distance analytically within linearized PB theory. Numerical results for the non-linear PB theory indicate strong enhancement of the tendency to mediate attractive interactions.
69 citations
TL;DR: A self-consistent mean-field model that includes the pH effect on the surface-charge density and the interactions between divalent ions and surface groups is analyzed, which provides the effects of polyelectrolyte line-chargedensity and monovalent salt on adsorption.
66 citations
TL;DR: In this paper, the complexation between a polyion and an oppositely charged spherical macroion in the framework of the primitive model has been studied by the use of Monte Carlo simulations.
Abstract: The complexation between a polyion and an oppositely charged spherical macroion in the framework of the
primitive model has been studied by the use of Monte Carlo simulations. The polyion length, linear charge
density, and bare persistence length are varied systematically, while the properties of the macroion are kept
constant. The polyion charge to macroion charge ratio is varied between 1/4 and 4. The structure of the
complex is investigated by direct visualization; polyion bead complexation probability; loop, tail, and train
characteristics; degree of overcharging; and tail joint probability functions. The strongest complexes are
observed for flexible chains, where the polyion is folded around the macroion. In the case of fully flexible
chains, a transition from a collapsed state to a fluctuating two-tail state and eventually to a one-tail state are
observed as the chain length is increased. As the stiffness is increased, several complex structures, such as
multiloop, single-loop, and solenoid arrangements, and finally a structure involving only a single contact
between the polyion and the macroion occur. In particular, for long and highly charged polyions, a transition
from the one-tail state to a two-tail state appears as the chain stiffness is increased. A discussion with recent
theories and other simulation studies is also provided.
56 citations