Papers by Ivana Pajic-Lijakovic
Materials Science Forum, 2005
The change in elastomer tensile moduli, as formulated in the Gaussian statistical theory of rubbe... more The change in elastomer tensile moduli, as formulated in the Gaussian statistical theory of rubber elasticity, with deformation, is considered both experimentally and theoretically. Gum elastomers of different structures and corresponding materials filled with carbon black, as reinforcing filler, are investigated experimentally. For all materials considered, the same scaling pattern with negative and low slope for small deformations, and positive and higher slope for large deformations is obtained, indicating two distinct mechanisms of elastic response. Most pronounced is the similarity of small deformation responses for filled materials. Considering the modulus as an elastic energy density gradient dependent on structure changes with deformation, and interpreting the changes for small deformations in terms of conformational energy change, the fractal dimension of a new type is formulated. It describes the decrease in elastomer network connectivity with deformations, which is discussed in terms of conformon dynamics. Possibilities of application of Faynman's path integral method and statistical method of random walk to the lattice are considered for the conformon, as well.
Starch-starke, May 31, 2019
This article has been accepted for publication and undergone full peer review but has not been th... more This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as
Seminars in Cell & Developmental Biology, Sep 1, 2023
arXiv (Cornell University), Oct 29, 2021
Although collective cell migration (CCM) is a highly coordinated and fine-tuned migratory mode, i... more Although collective cell migration (CCM) is a highly coordinated and fine-tuned migratory mode, instabilities in the form of cell swirling motion (CSM) often occur. The CSM represents a product of the active turbulence obtained at low Reynolds number which has a feedback impact to various processes such as morphogenesis, wound healing, and cancer invasion. The cause of this phenomenon is related to the viscoelasticity of multicellular systems in the context of cell residual stress accumulation. Particular interest of this work is to: (1) emphasize the roles of cell shear and normal residual stress accumulated during CCM in the appearance of CSM and (2) consider the dynamics of CSM from the standpoint of rheology. Inhomogeneous distribution of the cell residual stress leads to a generation the viscoelastic force which acts to suppress CCM and can induces the system rapid stiffening. This force together with the surface tension force and traction force is responsible for the appearance of the CSM. In this work, a review of existing literature about viscoelasticity caused by CCM is given along with assortment of published experimental findings, in order to invite experimentalists to test given theoretical considerations in multicellular systems.
Applied Physics A, Jul 12, 2023
arXiv (Cornell University), Feb 11, 2023
Movement of cell clusters along extracellular matrices (ECM) during tissue development, wound hea... more Movement of cell clusters along extracellular matrices (ECM) during tissue development, wound healing, and early stage of cancer invasion involve various interconnected migration modes such as: (1) cell movement within clusters, (2) cluster extension (wetting) and compression (de-wetting), and (3) directional cluster movement. It has become increasingly evident that dilational and volumetric viscoelasticity of cell clusters and their surrounding substrate significantly influence these migration modes through physical parameters such as: cell and matrix surface tensions, interfacial tension between cells and substrate, gradients of surface and interfacial tensions, as well as, the accumulation of cell and matrix residual stresses. Inhomogeneous distribution of cell surface tension along migrating cell cluster can appear as a consequence of different strength of cell-cell adhesion contacts and cell contractility between leader and follower cells. This inhomogeneity in the form of cell surface tension gradient influences cell movement within the cluster. However, this phenomenon has not been considered yet. The cell residual stress accumulation can reduce movement of epithelial-like cells, while physical properties of ECM such as the matrix surface tension gradient and matrix residual stress accumulation are responsible for directional cell migration. An inhomogeneous accumulation of the matrix stress leads to the establishment of a matrix stiffness gradient which guides directional cell migration. While the directional cell migration caused by the matrix stiffness gradient (i.e. durotaxis) has been widely elaborated, the structural changes of matrix surface caused by cell tractions which lead to the generation of the matrix surface tension gradient has not been considered yet. The main goal of this theoretical consideration is to clarify the roles of various physical parameters in collective cell migration based on the formulating biophysical model. This complex phenomenon is discussed on the model systems such as the movement of cell clusters on the collagen I gel matrix by simultaneously reviewing various experimental data with and without cells.
Frontiers in Physics, Sep 29, 2021
European Biophysics Journal, Jan 2, 2023
Morphogenesis, tissue regeneration and cancer invasion involve transitions in tissue morphology. ... more Morphogenesis, tissue regeneration and cancer invasion involve transitions in tissue morphology. These transitions, caused by collective cell migration (CCM), have been interpreted as active wetting/dewetting transitions. This phenomenon is considered on model system such as wetting of cell aggregate on rigid substrate which includes cell aggregate movement and isotropic/anisotropic spreading of cell monolayer around the aggregate depending on the substrate rigidity and aggregate size. This model system accounts for the transition between 3D epithelial aggregate and 2D cell monolayer as a product of: (1) tissue surface tension, (2) surface tension of substrate matrix, (3) cell-matrix interfacial tension, (4) interfacial tension gradient, (5) viscoelasticity caused by CCM, and (6) viscoelasticity of substrate matrix. These physical parameters depend on the cell contractility and state of cell-cell and cell matrix adhesion contacts, as well as, the stretching/compression of cellular systems caused by CCM. Despite extensive research devoted to study cell wetting, we still do not understand interplay among these physical parameters which induces oscillatory trend of cell rearrangement. This review focuses on these physical parameters in governing the cell rearrangement in the context of epithelial aggregate wetting.de-wetting, and on the modelling approaches aimed at reproducing and understanding these biological systems. In this context, we do not only review previously-published bio-physics models for cell rearrangement caused by CCM, but also propose new extensions of those models in order to point out the interplay between cell-matrix interfacial tension and epithelial viscoelasticity and the role of the interfacial tension gradient in cell spreading.
European Physical Journal Plus, Jul 1, 2021
Although collective cell migration (CCM) is a highly coordinated migratory mode, perturbations in... more Although collective cell migration (CCM) is a highly coordinated migratory mode, perturbations in the form of jamming state transitions and vice versa often occur even in 2D. These perturbations are involved in various biological processes, such as embryogenesis, wound healing and cancer invasion. CCM induces accumulation of cell residual stress which has a feedback impact to cell packing density. Density-mediated change of cell mobility influences the state of viscoelasticity of multicellular systems and on that base the jamming state transition. Although a good comprehension of how cells collectively migrate by following molecular rules has been generated, the impact of cellular rearrangements on cell viscoelasticity remains less understood. Thus, considering the density driven evolution of viscoelasticity caused by reduction of cell mobility could result in a powerful tool in order to address the contribution of cell jamming state transition in CCM and help to understand this important but still controversial topic. In addition, five viscoelastic states gained within three regimes: (1) convective regime, (2) conductive regime, and (3) damped-conductive regime was discussed based on the modeling consideration with special emphasis of jamming and unjamming states.
Food Hydrocolloids, Dec 1, 2016
Abstract The influence of concentration and temperature on the rheological properties of tomato p... more Abstract The influence of concentration and temperature on the rheological properties of tomato pomace dispersions obtained by rehydration of lyophilized and grinded tomato pomace was investigated in this paper. Examined systems comprised of different lyophilized tomato pomace concentrations (18.2, 16.7, 14.3, 12.5, 11.1, 10.0, and 9.1%) heat treated at two different temperatures (60 °C and 100 °C) during 30 min. According to microstructure analysis of the studied system, it could be simplified as the composite consisting of insoluble particles surrounded by the pectin network. The system behaves as viscoelastic solid (G′ > G″ at all angular velocities), and therefore the static modulus of elasticity, the effective modulus and the damping coefficient were determined by application of modified fractional Kelvin-Voigt model. The influence of particle concentration on the rheological properties of tomato pomace system is dominant in comparison to the content and composition of pectin solubilised in the serum. Concentrated tomato pomace dispersions are much stiffer (G′ values an order of magnitude higher) than the composite systems. Heat treatment at higher temperature (100 °C) decreases the stiffness of the system by breaking of non-covalent bonds between dispersed tomato particles and surrounding pectin network. Storage modulus as a function of the tomato pomace lyophilizate concentration was considered within three regimes (regime 1 – concentration 16.7%) that could be used as the base for formulation of tomato pomace-based products with different desirable consistencies, such as sauce, ketchup and marmalade.
Acs Symposium Series, Sep 29, 2005
Design of mechanical properties, especially the relation between tensile and dynamic moduli in te... more Design of mechanical properties, especially the relation between tensile and dynamic moduli in terms of chain conformational statistics is considered. Data on new elastomer blends with gradient properties, able for mixingon molecular level and partial networking with separation of phases, are analyzed in parallel to classical commodity materials. Especial attention is paid to synergetic effects of the increase of blend modulus, relative to moduli obtained by linear "rule of mixtures" for component polymer moduli, described by Kleiner-Karasz-MacKnight equation, and new models based on self-similar scaling of elastomer network dynamics. New data on model blends exposing synergetic effects with the change of conformational statistics are presented as well.
arXiv (Cornell University), Jun 2, 2023
Collective cell migration is essential for a wide range of biological processes such as: morphoge... more Collective cell migration is essential for a wide range of biological processes such as: morphogenesis, wound healing, and cancer spreading. However, it is well known that migrating epithelial collectives frequently undergo jamming, stay trapped some period of time, and then start migration again. Consequently, only a part of epithelial cells actively contributes to the tissue development. In contrast to epithelial cells, migrating mesenchymal collectives successfully avoid the jamming. It has been confirmed that the epithelial unjamming cannot be treated as the epithelial-to-mesenchymal transition. Some other mechanism is responsible for the epithelial jamming/unjamming. Despite extensive research devoted to study the cell jamming/unjamming, we still do not understand the origin of this phenomenon. The origin is connected to physical factors such as: the cell compressive residual stress accumulation and surface characteristics of migrating (unjamming) and resting (jamming) epithelial clusters which depend primarily on the strength of cell-cell adhesion contacts and cell contractility. The main goal of this theoretical consideration is to clarify these cause-consequence relations.
Elsevier eBooks, 2021
Viscoelasticity of multicellular systems caused by collective cell migration depends on (1) visco... more Viscoelasticity of multicellular systems caused by collective cell migration depends on (1) viscoelasticity of migrating clusters, (2) viscoelasticity of surrounding resting cells and (3) the size, slip effects and thickness of the biointerface. A previously developed model for a sharp biointerface is expanded for the case of a finite biointerface based on thermodynamic and rheological considerations to estimate the influence of the biointerface properties on viscoelasticity. These properties of the interface layer are one of the key factors which influence the overall properties of the mixture, such as its viscoelasticity. Sliding of cell clusters through dense surroundings induces generation of significant shear stress, within the biointerface, which influences (1) the active (contractile) or passive state of single cells and (2) the state of cell-cell adhesion contacts. Cells retain collectivity in migration patterns even upon a reduction of cell-cell adhesion caused by stress generation. A greater size to the biointerface leads to the weakening of multicellular systems for the same volume fraction of migrating cells due to energy dissipation. Various factors such as (1) increase of the interface size, (2) reduction in slip effects under the constant thickness of the biointerface and (3) decrease in the biointerface thickness under constant slip effects induce an increase of the shear rate as well as the overall energy dissipation and can lead to circular cell movement within the biointerface layer. Additional experiments at subcellular and cellular levels are needed to determine the influence of mechanical factors on collective cell migration.
Advances in Colloid and Interface Science, May 1, 2023
Seminars in Cell & Developmental Biology, Sep 1, 2023
Gels, Aug 1, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Progress in Biophysics & Molecular Biology, Sep 1, 2022
Although collective cell migration (CCM) is a highly coordinated and ordered migratory mode, pert... more Although collective cell migration (CCM) is a highly coordinated and ordered migratory mode, perturbations in the form of mechanical waves appear even in 2D. These perturbations caused by the viscoelastic nature of cell rearrangement are involved in various biological processes, such as embryogenesis, wound healing and cancer invasion. The mechanical waves, as a product of the active turbulence occurred at low Reynolds number, represent an oscillatory change in cell velocity and the relevant rheological parameters. The velocity oscillations, in the form of forward and backward flows, are driven by: viscoelastic force, surface tension force, and traction force. The viscoelastic force represents a consequence of inhomogeneous distribution of cell residual stress accumulated during CCM. This cause-consequence relation is considered on a model system such as the cell monolayer free expansion. The collision of forward and backward flows causes an increase in cell packing density which has a feedback impact on the tissue viscoelasticity and on that base influences the tissue stiffness. The evidence of how the tissue stiffness is changed near the cell jamming is conflicting. To fill this gap, we discussed the density driven change in the tissue viscoelasticity by accounting for the cell pseudo-phase transition from active (contractile) to passive (non-contractile) state appeared near cell jamming in the rheological modeling consideration.
Acta Physica Polonica A, Aug 1, 2011
The system of living cells closed in a polymer matrix and self-organized into clusters is conside... more The system of living cells closed in a polymer matrix and self-organized into clusters is considered, extending free volume concept developed for complex system interactions quantification in statistical mechanics of jammed state of matter. Possibility of extension of Edwards concept of compactivity and angorisity developed for hard irregular grains with friction to living cell systems, is considered. Existences of scaling laws for cell colony grow, related to their self assembling and response to polymer hydrogel micro-environment constrains, is analyzed as function of rate of cluster density increase. Based on the theory proposed are developed relations, connecting cluster properties that are difficult to measure, to data from standard cell cultivation experiments. The model also provides possibilities of incorporation data on single cell behavior, available from modern nano-rheology measurements, into cluster
International Journal of Molecular Sciences
Red blood cell (RBC) deformability, expressing their ability to change their shape, allows them t... more Red blood cell (RBC) deformability, expressing their ability to change their shape, allows them to minimize their resistance to flow and optimize oxygen delivery to the tissues. RBC with reduced deformability may lead to increased vascular resistance, capillary occlusion, and impaired perfusion and oxygen delivery. A reduction in deformability, as occurs during RBC physiological aging and under blood storage, is implicated in the pathophysiology of diverse conditions with circulatory disorders and anemias. The change in RBC deformability is associated with metabolic and structural alterations, mostly uncharacterized. To bridge this gap, we analyzed the membrane protein levels, using mass spectroscopy, of RBC with varying deformability determined by image analysis. In total, 752 membrane proteins were identified. However, deformability was positively correlated with the level of only fourteen proteins, with a highly significant inter-correlation between them. These proteins are invol...
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Papers by Ivana Pajic-Lijakovic