Extracellular biophysical cues have a profound influence on a wide range of cell behaviors, including growth, motility, differentiation, apoptosis, gene expression, adhesion, and signal transduction. ...Cells not only respond to definitively mechanical cues from the extracellular matrix (ECM) but can also sometimes alter the mechanical properties of the matrix and hence influence subsequent matrix-based cues in both physiological and pathological processes. Interactions between cells and materials in vitro can modify cell phenotype and ECM structure, whether intentionally or inadvertently. Interactions between cell and matrix mechanics in vivo are of particular importance in a wide variety of disorders, including cancer, central nervous system injury, fibrotic diseases, and myocardial infarction. Both the in vitro and in vivo effects of this coupling between mechanics and biology hold important implications for clinical applications.
The adhesion and proliferation of bacteria on abiotic surfaces pose challenges related to human infection, including subsequent formation of antibiotic-resistant biofilms in both healthcare and ...industrial applications. Although the design of antibacterial materials is a longstanding effort, the surface properties that modulate adhesion of viable bacteriathe critical first step in biofilm formationhave been difficult to decouple. This partial and limited success is due chiefly to two factors. First, bacteria cells exhibit multiple, complex adhesion mechanisms that vary with bacteria strain, rapid genetic mutations within a given strain, and mutable environmental stimuli such as nutrient levels and fluid velocities. Second, there exist only a limited number of studies that systematically characterize or vary the physical, chemical, and mechanical properties of potential antimicrobial materials. Here, we briefly review the dominant strategies for antimicrobial material surface design, including the advantages and limitations of approaches developed via synthetic and natural polymers. We then consider polyelectrolyte multilayers (PEMs) as a versatile materials platform to adopt and integrate these strategies, as well as to elucidate the individual contributions of tunable material properties that limit viable bacteria adhesion. Together, these findings suggest that PEMs can be tailored to leverage the key advantages of bacterial adhesion resistance, contact killing, and biocide leaching strategies for a wide range of antimicrobial surface applications.
Microenvironments of biological cells are dominated in vivo by macromolecular crowding and resultant excluded volume effects. This feature is absent in dilute in vitro cell culture. Here, we induced ...macromolecular crowding in vitro by using synthetic macromolecular globules of nm-scale radius at physiological levels of fractional volume occupancy. We quantified the impact of induced crowding on the extracellular and intracellular protein organization of human mesenchymal stem cells (MSCs) via immunocytochemistry, atomic force microscopy (AFM), and AFM-enabled nanoindentation. Macromolecular crowding in extracellular culture media directly induced supramolecular assembly and alignment of extracellular matrix proteins deposited by cells, which in turn increased alignment of the intracellular actin cytoskeleton. The resulting cell-matrix reciprocity further affected adhesion, proliferation, and migration behavior of MSCs. Macromolecular crowding can thus aid the design of more physiologically relevant in vitro studies and devices for MSCs and other cells, by increasing the fidelity between materials synthesized by cells in vivo and in vitro.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract Mesenchymal stem and stromal cells (MSCs) hold potential to treat a broad range of clinical indications, but clinical translation has been limited to date due in part to challenges with ...batch-to-batch reproducibility of potential critical quality attributes (pCQAs) that can predict potency/efficacy. Here, we designed and implemented a microcarrier-microbioreactor approach to cell therapy manufacturing, specific to anchorage-dependent cells such as MSCs. We sought to assess whether increased control of the biochemical and biophysical environment had the potential to create product with consistent presentation and elevated expression of pCQAs relative to established manufacturing approaches in tissue culture polystyrene (TCPS) flasks. First, we evaluated total cell yield harvested from dissolvable, gelatin microcarriers within a microbioreactor cassette (Mobius Breez) or a flask control with matched initial cell seeding density and culture duration. Next, we identified 24 genes implicated in a therapeutic role for a specific motivating indication, acute respiratory distress syndrome (ARDS); expression of these genes served as our pCQAs for initial in vitro evaluation of product potency. We evaluated mRNA expression for three distinct donors to assess inter-donor repeatability, as well as for one donor in three distinct batches to assess within-donor, inter-batch variability. Finally, we assessed gene expression at the protein level for a subset of the panel to confirm successful translation. Our results indicated that MSCs expanded with this microcarrier-microbioreactor approach exhibited reasonable donor-to-donor repeatability and reliable batch-to-batch reproducibility of pCQAs. Interestingly, the baseline conditions of this microcarrier-microbioreactor approach also significantly improved expression of several key pCQAs at the gene and protein expression levels and reduced total media consumption relative to TCPS culture. This proof-of-concept study illustrates key benefits of this approach to therapeutic cell process development for MSCs and other anchorage-dependent cells that are candidates for cell therapies.
Nanoparticle (NP) stiffness has been shown to significantly impact circulation time and biodistribution in anticancer drug delivery. In particular, the relationship between particle stiffness and ...tumor accumulation and penetration in vivo is an important phenomenon to consider in optimizing NP-mediated tumor delivery. Layer-by-layer (LbL) NPs represent a promising class of multifunctional nanoscale drug delivery carriers. However, there has been no demonstration of the versatility of LbL systems in coating systems with different stiffnesses, and little is known about the potential role of LbL NP stiffness in modulating in vivo particle trafficking, although NP modulus has been recently studied for its impact on pharmacokinetics. LbL nanotechnology enables NPs to be functionalized with uniform coatings possessing molecular tumor-targeting properties, independent of the NP core stiffness. Here, we report that the stiffness of LbL NPs is directly influenced by the mechanical properties of its underlying liposomal core, enabling the modulation and optimization of LbL NP stiffness while preserving LbL NP outer layer tumor-targeting and stealth properties. We demonstrate that the stiffness of LbL NPs has a direct impact on NP pharmacokinetics, organ and tumor accumulation, and tumor penetration-with compliant LbL NPs having longer elimination half-life, higher tumor accumulation, and higher tumor penetration. Our findings underscore the importance of NP stiffness as a design parameter in enhancing the delivery of LbL NP formulations.
realistic molecular model of cement hydrates Pellenq, Roland J.-M; Kushima, Akihiro; Shahsavari, Rouzbeh ...
Proceedings of the National Academy of Sciences - PNAS,
09/2009, Letnik:
106, Številka:
38
Journal Article
Recenzirano
Odprti dostop
Despite decades of studies of calcium-silicate-hydrate (C-S-H), the structurally complex binder phase of concrete, the interplay between chemical composition and density remains essentially ...unexplored. Together these characteristics of C-S-H define and modulate the physical and mechanical properties of this "liquid stone" gel phase. With the recent determination of the calcium/silicon (C/S = 1.7) ratio and the density of the C-S-H particle (2.6 g/cm³) by neutron scattering measurements, there is new urgency to the challenge of explaining these essential properties. Here we propose a molecular model of C-S-H based on a bottom-up atomistic simulation approach that considers only the chemical specificity of the system as the overriding constraint. By allowing for short silica chains distributed as monomers, dimers, and pentamers, this C-S-H archetype of a molecular description of interacting CaO, SiO₂, and H₂O units provides not only realistic values of the C/S ratio and the density computed by grand canonical Monte Carlo simulation of water adsorption at 300 K. The model, with a chemical composition of (CaO)₁.₆₅(SiO₂)(H₂O)₁.₇₅, also predicts other essential structural features and fundamental physical properties amenable to experimental validation, which suggest that the C-S-H gel structure includes both glass-like short-range order and crystalline features of the mineral tobermorite. Additionally, we probe the mechanical stiffness, strength, and hydrolytic shear response of our molecular model, as compared to experimentally measured properties of C-S-H. The latter results illustrate the prospect of treating cement on equal footing with metals and ceramics in the current application of mechanism-based models and multiscale simulations to study inelastic deformation and cracking.
Actuator operation in increasingly extreme and remote conditions requires materials that reliably sense and actuate at elevated temperatures, and over a range of gas environments. Design of such ...materials will rely on high-temperature, high-resolution approaches for characterizing material actuation in situ. Here, we demonstrate a novel type of high-temperature, low-voltage electromechanical oxide actuator based on the model material Pr
Ce
O
(PCO). Chemical strain and interfacial stress resulted from electrochemically pumping oxygen into or out of PCO films, leading to measurable film volume changes due to chemical expansion. At 650 °C, nanometre-scale displacement and strain of >0.1% were achieved with electrical bias values <0.1 V, low compared to piezoelectrically driven actuators, with strain amplified fivefold by stress-induced structural deflection. This operando measurement of films 'breathing' at second-scale temporal resolution also enabled detailed identification of the controlling kinetics of this response, and can be extended to other electrochemomechanically coupled oxide films at extreme temperatures.
Two-dimensional (2D) materials can uniquely span the physical dimensions of a surrounding composite matrix in the limit of maximum reinforcement. However, the alignment and assembly of continuous 2D ...components at high volume fraction remain challenging. We use a stacking and folding method to generate aligned graphene/polycarbonate composites with as many as 320 parallel layers spanning 0.032 to 0.11 millimeters in thickness that significantly increases the effective elastic modulus and strength at exceptionally low volume fractions of only 0.082%. An analogous transverse shear scrolling method generates Archimedean spiral fibers that demonstrate exotic, telescoping elongation at break of 110%, or 30 times greater than Kevlar. Both composites retain anisotropic electrical conduction along the graphene planar axis and transparency. These composites promise substantial mechanical reinforcement, electrical, and optical properties at highly reduced volume fraction.
The emergence of heterogeneity in putative mesenchymal stem cell (MSC) populations during in vitro expansion is not appreciated fully by the various communities who study, engineer, and use such stem ...cells. However, this functional diversity holds direct implications for basic research and therapeutic applications of MSCs that require predictable phenotypic function and efficacy. Despite numerous clinical trials pursuing MSC therapies, the in vitro expansion of homogeneous populations to therapeutically relevant quantities remains an elusive goal. Variation in MSC cultures has been noted not only among donors and within populations expanded from the same donor, but also debatably within single‐cell‐derived colonies. The potential for even intracolony heterogeneity suggests that any purified subpopulation will inevitably become heterogeneous upon further expansion under current culture conditions. Here, we review the noted or retrospective evidence of intracolony MSC heterogeneity, to facilitate discussion of its possible causes and potential solutions to its mitigation. This analysis suggests that functional diversity within an MSC colony must be considered in design of experiments and trials for even nonclonal stem cell populations, and can be mitigated or even exploited when the mechanisms of onset are better understood. Stem Cells 2016;34:1135–1141
Among individual cells of the same source and type, the complex shear modulus G∗ exhibits a large log-normal distribution that is the result of spatial, temporal, and intrinsic variations. Such large ...distributions complicate the statistical evaluation of pharmacological treatments and the comparison of different cell states. However, little is known about the characteristic features of cell-to-cell variation. In this study, we investigated how this variation depends on the spatial location within the cell and on the actin filament cytoskeleton, the organization of which strongly influences cell mechanics. By mechanically probing fibroblasts arranged on a microarray, via atomic force microscopy, we observed that the standard deviation σ of G∗ was significantly reduced among cells in which actin filaments were depolymerized. The parameter σ also exhibited a subcellular spatial dependence. Based on our findings regarding the frequency dependence of σ of the storage modulus G′, we proposed two types of cell-to-cell variation in G′ that arise from the purely elastic and the frequency-dependent components in terms of the soft glassy rheology model of cell deformability. We concluded that the latter inherent cell-to-cell variation can be reduced greatly by disrupting actin networks, by probing at locations within the cell nucleus boundaries distant from the cell center, and by measuring at high loading frequencies.
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