Elasticity and adhesion of resting and lipopolysaccharide-stimulated macrophages

Biomechanics of Macrophages on Disordered Surface Nanotopography

Macrophages are involved in every stage of the innate/inflammatory immune responses in the body tissues, including the resolution of the reaction, and they do so in close collaboration with the extracellular matrix (ECM). Simplified substrates with nanotopographical features attempt to mimic the structural properties of the ECM to clarify the functional features of the interaction of the ECM with macrophages. We still have a limited understanding of the macrophage behavior upon interaction with disordered nanotopography, especially with features smaller than 10 nm. Here, we combine atomic force microscopy (AFM), finite element modeling (FEM), and quantitative biochemical approaches in order to understand the mechanotransduction from the nanostructured surface into cellular responses. AFM experiments show a decrease of macrophage stiffness, measured with the Young's modulus, as a biomechanical response to a nanostructured (ns-) ZrOx surface. FEM experiments suggest that ZrOx surfaces with increasing roughness represent weaker mechanical boundary conditions. The mechanical cues from the substrate are transduced into the cell through the formation of integrin-regulated focal adhesions and cytoskeletal reorganization, which, in turn, modulate cell biomechanics by downregulating cell stiffness. Surface nanotopography and consequent biomechanical response impact the overall behavior of macrophages by increasing movement and phagocytic ability without significantly influencing their inflammatory behavior. Our study suggests a strong potential of surface nanotopography for the regulation of macrophage functions, which implies a prospective application relative to coating technology for biomedical devices.

Two-component macrophage model for active phagocytosis with pseudopod formation

Macrophage phagocytosis is critical for the immune response, homeostasis regulation, and tissue repair. This intricate process involves complex changes in cell morphology, cytoskeletal reorganization, and various receptor-ligand interactions controlled by mechanical constraints. However, there is a lack of comprehensive theoretical and computational models that investigate the mechanical process of phagocytosis in the context of cytoskeletal rearrangement. To address this issue, we propose a novel coarse-grained mesoscopic model that integrates a fluid-like cell membrane and a cytoskeletal network to study the dynamic phagocytosis process. The growth of actin filaments results in the formation of long and thin pseudopods, and the initial cytoskeleton can be disassembled upon target entry and reconstructed after phagocytosis. Through dynamic changes in the cytoskeleton, our macrophage model achieves active phagocytosis by forming a phagocytic cup utilizing pseudopods in two distinct ways. We have developed a new algorithm for modifying membrane area to prevent membrane rupture and ensure sufficient surface area during phagocytosis. In addition, the bending modulus, shear stiffness, and cortical tension of the macrophage model are investigated through computation of the axial force for the tubular structure and micropipette aspiration. With this model, we simulate active phagocytosis at the cytoskeletal level and investigate the mechanical process during the dynamic interplay between macrophage and target particles.

Radical-Generating Activity, Phagocytosis, and Mechanical Properties of Four Phenotypes of Human Macrophages

Macrophages are the major players and orchestrators of inflammatory response. Expressed proteins and secreted cytokines have been well studied for two polar macrophage phenotypes-pro-inflammatory M1 and anti-inflammatory regenerative M2, but little is known about how the polarization modulates macrophage functions. In this study, we used biochemical and biophysical methods to compare the functional activity and mechanical properties of activated human macrophages differentiated from monocyte with GM-CSF (M0_GM) and M-CSF (M0_M) and polarized into M1 and M2 phenotypes, respectively. Unlike GM-CSF, which generates dormant cells with low activity, M-CSF confers functional activity on macrophages. M0_M and M2 macrophages had very similar functional characteristics-high reactive oxygen species (ROS) production level, and higher phagocytosis and survival compared to M1, while M1 macrophages showed the highest radical-generating activity but the lowest phagocytosis and survival among all phenotypes. All phenotypes decreased their height upon activation, but only M1 and M2 cells increased in stiffness, which can indicate a decrease in the migration ability of these cells and changes in their interactions with other cells. Our results demonstrated that while mechanical properties differ between M0 and polarized cells, all four phenotypes of monocyte-derived macrophages differ in their functional activities, namely in cytokine secretion, ROS production, and phagocytosis. Within the broad continuum of human macrophages obtained in experimental models and existing in vivo, there is a diversity of phenotypes with varying combinations of both markers and functional activities.

Strategy for Nonenzymatic Harvesting of Cells via Decoupling of Adhesive and Disjoining Domains of Nanostructured Stimulus-Responsive Polymer Films

The nanostructured polymer film introduces a novel mechanism of nonenzymatic cell harvesting by decoupling solid cell-adhesive and soft stimulus-responsive cell-disjoining areas on the surface. The key characteristics of this architecture are the decoupling of adhesion from detachment and the impermeability to the integrin protein complex of the adhesive domains. This surface design eliminates inherent limitations of thermoresponsive coatings, namely, the necessity for the precise thickness of the coating, grafting or cross-linking density, and material of the basal substrate. The concept is demonstrated with nanostructured thermoresponsive films made of cell-adhesive epoxy photoresist domains and cell-disjoining poly(N-isopropylacrylamide) brush domains.

Deep learning strategy for small dataset from atomic force microscopy mechano-imaging on macrophages phenotypes

The cytoskeleton is involved during movement, shaping, resilience, and functionality in immune system cells. Biomarkers such as elasticity and adhesion can be promising alternatives to detect the status of cells upon phenotype activation in correlation with functionality. For instance, professional immune cells such as macrophages undergo phenotype functional polarization, and their biomechanical behaviors can be used as indicators for early diagnostics. For this purpose, combining the biomechanical sensitivity of atomic force microscopy (AFM) with the automation and performance of a deep neural network (DNN) is a promising strategy to distinguish and classify different activation states. To resolve the issue of small datasets in AFM-typical experiments, nanomechanical maps were divided into pixels with additional localization data. On such an enlarged dataset, a DNN was trained by multimodal fusion, and the prediction was obtained by voting classification. Without using conventional biomarkers, our algorithm demonstrated high performance in predicting the phenotype of macrophages. Moreover, permutation feature importance was employed to interpret the results and unveil the importance of different biophysical properties and, in turn, correlated this with the local density of the cytoskeleton. While our results were demonstrated on the RAW264.7 model cell line, we expect that our methodology could be opportunely customized and applied to distinguish different cell systems and correlate feature importance with biophysical properties to unveil innovative markers for diagnostics.

Probing soft fibrous materials by indentation

Indentation is often used to measure the stiffness of soft materials whose main structural component is a network of filaments, such as the cellular cytoskeleton, connective tissue, gels, and the extracellular matrix. For elastic materials, the typical procedure requires fitting the experimental force-displacement curve with the Hertz model, which predicts that f=kδ1.5 and k is proportional to the reduced modulus of the indented material, E/(1-ν2). Here we show using explicit models of fiber networks that the Hertz model applies to indentation in network materials provided the indenter radius is larger than approximately 12lc, where lc is the mean segment length of the network. Using smaller indenters leads to a relation between force and indentation displacement of the form f=kδq, where q is observed to increase with decreasing indenter radius. Using the Hertz model to interpret results of indentations in network materials using small indenters leads to an inferred modulus smaller than the real modulus of the material. The origin of this departure from the classical Hertz model is investigated. A compacted, stiff network region develops under the indenter, effectively increasing the indenter size and modifying its shape. This modification is marginal when large indenters are used. However, when the indenter radius is small, the effect of the compacted layer is pronounced as it changes the indenter profile from spherical towards conical. This entails an increase of exponent q above the value of 1.5 corresponding to spherical indenters. STATEMENT OF SIGNIFICANCE: The article presents a study of indentation in network biomaterials and demonstrates a size effect which precludes the use of the Hertz model to infer the elastic constants of the material. The size effect occurs once the indenter radius is smaller than approximately 12 times the mean segment length of the network. This result provides guidelines for the selection of indentation conditions that guarantee the applicability of the Hertz model. At the same time, the finding may be used to infer the mean segment length of the network based on indentations with indenters of various sizes. Hence, the method can be used to evaluate this structural parameter which is not easily accessible in experiments.

Topography and mechanical measurements of primary Schwann cells and neuronal cells with atomic force microscope for understanding and controlling nerve growth

Peripheral nerve injuries require a piece of substantial information for a satisfactory treatment. The prior peripheral nerve injury knowledge, can improve nerve repair, and its growth at molecular and cellular level. In this study, we employed an atomic force microscope (AFM) to investigate the topography and mechanical properties of the primary Schwann cells and neuronal cells. Tapping mode images and contact points force-volume maps provide the cells topography. Two different probes were used to acquire the micro and nanomechanical properties of the primary Schwann cells, NG-108-15 neuronal cells, and growth cones. Moreover, the sharp probe was only used to investigate neurites nanomechanics. A significant difference in the elastic moduli found between primary Schwann cells, and neuronal cells, with both probes, with consistent results. The elastic moduli of the growth cones were found higher, than the neuronal cells and primary Schwann cells, with both probes. Furthermore, the modulus variations were also found between neurites. These results have significant implications for a better understanding of the peripheral nerve system (PNS) in terms of defining the optimal pattern surface and nerve guidance conduits.

Polymer- and lipid-based gene delivery technology for CAR T cell therapy

Chimeric antigen receptor T cell (CAR T cell) therapy is a revolutionary approach approved by the FDA and EMA to treat B cell malignancies and multiple myeloma. The production of these T cells has been done through viral vectors, which come with safety concerns, high cost and production challenges, and more recently also through electroporation, which can be extremely cytotoxic. In this context, nanosystems can constitute an alternative to overcome the challenges associated with current methods, resulting in a safe and cost-effective platform. However, the barriers associated with T cells transfection show that the design and engineering of novel approaches in this field are highly imperative. Here, we present an overview from CAR constitution to transfection technologies used in T cells, highlighting the lipid- and polymer-based nanoparticles as a potential delivery platform. Specifically, we provide examples, strengths and weaknesses of nanosystem formulations, and advances in nanoparticle design to improve transfection of T cells. This review will guide the researchers in the design and development of novel nanosystems for next-generation CAR T therapeutics.

Ceragenin CSA-13 displays high antibacterial efficiency in a mouse model of urinary tract infection

Ceragenins (CSAs) are synthetic, lipid-based molecules that display activities of natural antimicrobial peptides. Previous studies demonstrated their high in vitro activity against pathogens causing urinary tract infections (UTIs), but their efficiency in vivo was not explored to date. In this study, we aimed to investigate the bactericidal efficiency of ceragenins against E. coli (Xen14 and clinical UPEC strains) isolates both in vitro and in vivo, as well to explore CSA-13 biodistribution and ability to modulate nanomechanical alterations of infected tissues using animal model of UTI. CSA-44, CSA-131 and particularly CSA-13 displayed potent bactericidal effect against tested E. coli strains, and this effect was mediated by induction of oxidative stress. Biodistribution studies indicated that CSA-13 accumulates in kidneys and liver and is eliminated with urine and bile acid. We also observed that ceragenin CSA-13 reverses infection-induced alterations in mechanical properties of mouse bladders tissue, which confirms the preventive role of CSA-13 against bacteria-induced tissue damage and potentially promote the restoration of microenvironment with biophysical features unfavorable for bacterial growth and spreading. These data justify the further work on employment of CSA-13 in the treatment of urinary tract infections.

Adjustable biodegradability of low-swelling hydrogels prepared from recombinant peptides based on human collagen type 1

An ideal hydrogel for tissue engineering and regenerative therapy is cytocompatible, biocompatible, and has low-swelling characteristics. Recently, a novel low-swelling hydrogel with a homogenous structure was developed by crosslinking a recombinant peptide, modeled on human collagen type 1 (RCPhC1), with a four-arm polyethylene glycol (tetra-PEG). Here, we hypothesized that the biodegradability of the RCPhC1 hydrogel was adjustable by altering its initial polymer concentration. Three types of RCPhC1 hydrogels were prepared using the initial polymer at different concentrations, and their morphology, swelling ratio, collagenase degradability, cytocompatibility, biocompatibility, and biodegradability were compared. The results revealed a low swelling ratio. The higher the concentration of the initial polymer, the longer it took for it to be degraded by collagenase. The average cell viability ratio was over 92% when using the direct contact method, which suggests that the hydrogels have excellent cytocompatibility. No death, tumorigenesis, exposure of the implants, or skin necrosis associated with the subcutaneous implantation of the hydrogels was found in mice in vivo. Moreover, histological evaluation revealed the formation of a thin fibrous capsule, which suggests an acceptable biocompatibility. Furthermore, as hypothesized, it was confirmed that the biodegradability can be adjusted by changing the initial polymer concentration. Collectively, the ability to fine-tune the biodegradability of RCPhC1 hydrogels demonstrates their potential for use in various clinical applications.

Biomaterial-based physical regulation of macrophage behaviour

Macrophages play a critical role in regulating immune reactions induced by implanted biomaterials. They are highly plastic and in response to diverse stimuli in the microenvironment can exhibit a spectrum of phenotypes and functions. In addition to biochemical signals, the physical properties of biomaterials are becoming increasingly appreciated for their significant impact on macrophage behaviour, and the underlying mechanisms deserve more in-depth investigations. This review first summarises the effects of key physical cues - including stiffness, topography, physical confinement and applied force - on macrophage behaviour. Then, it reviews the current knowledge of cellular sensing and transduction of physical cues into intracellular signals. Finally, it discusses the major challenges in understanding mechanical regulation that could provide insights for biomaterial design.

Inhibition of toll-like receptor 4 protects against inflammation-induced mechanobiological alterations to intervertebral disc cells

Intervertebral disc (IVD) degeneration is associated with elevated levels of inflammatory cytokines implicated in disease aetiology and matrix degradation. Toll-like receptor-4 (TLR4) has been shown to participate in the inflammatory responses of the nucleus pulposus (NP) and its levels are upregulated in disc degeneration. Activation of TLR4 in NP cells leads to significant, persistent changes in cell biophysical properties, including hydraulic permeability and osmotically active water content, as well as alterations to the actin cytoskeleton. The study hypothesis was that inflammation-induced changes to cellular biomechanical properties and actin cytoskeleton of NP cells could be prevented by inhibiting TLR4 signalling. Isolated NP cells from bovine discs were treated with lipopolysaccharide (LPS), the best studied TLR4 agonist, with or without treatment with the TLR4 inhibitor TAK-242. Cellular volume regulation responses to step osmotic loading were measured and the transient volume-response was captured by time-lapse microscopy. Volume-responses were analysed using mixture theory framework to investigate hydraulic permeability and osmotically active intracellular water content. Hydraulic permeability and cell radius were significantly increased with LPS treatment and these changes were blocked in cells treated with TAK-242. LPS-induced remodelling of cortical actin and IL-6 upregulation were also mitigated by TAK-242 treatment. These findings indicated that TLR4 signalling participated in NP cell biophysical regulation and may be an important target for mitigating altered cell responses observed in IVD inflammation and degeneration.

Viscoelastic properties of white and gray matter-derived microglia differentiate upon treatment with lipopolysaccharide but not upon treatment with myelin

Background

The biomechanical properties of the brain have increasingly been shown to relate to brain pathology in neurological diseases, including multiple sclerosis (MS). Inflammation and demyelination in MS induce significant changes in brain stiffness which can be linked to the relative abundance of glial cells in lesions. We hypothesize that the biomechanical, in addition to biochemical, properties of white (WM) and gray matter (GM)-derived microglia may contribute to the differential microglial phenotypes as seen in MS WM and GM lesions.

Methods

Primary glial cultures from WM or GM of rat adult brains were treated with either lipopolysaccharide (LPS), myelin, or myelin+LPS for 24 h or left untreated as a control. After treatment, microglial cells were indented using dynamic indentation to determine the storage and loss moduli reflecting cell elasticity and cell viscosity, respectively, and subsequently fixed for immunocytochemical analysis. In parallel, gene expression of inflammatory-related genes were measured using semi-quantitative RT-PCR. Finally, phagocytosis of myelin was determined as well as F-actin visualized to study the cytoskeletal changes.

Results

WM-derived microglia were significantly more elastic and more viscous than microglia derived from GM. This heterogeneity in microglia biomechanical properties was also apparent when treated with LPS when WM-derived microglia decreased cell elasticity and viscosity, and GM-derived microglia increased elasticity and viscosity. The increase in elasticity and viscosity observed in GM-derived microglia was accompanied by an increase in Tnfα mRNA and reorganization of F-actin which was absent in WM-derived microglia. In contrast, when treated with myelin, both WM- and GM-derived microglia phagocytose myelin decrease their elasticity and viscosity.

Conclusions

In demyelinating conditions, when myelin debris is phagocytized, as in MS lesions, it is likely that the observed differences in WM- versus GM-derived microglia biomechanics are mainly due to a difference in response to inflammation, rather than to the event of demyelination itself. Thus, the differential biomechanical properties of WM and GM microglia may add to their differential biochemical properties which depend on inflammation present in WM and GM lesions of MS patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02134-x.

Increasing AFM colloidal probe accuracy by optical tweezers

A precise determination of the cantilever spring constant is the critical point of all colloidal probe experiments. Existing methods are based on approximations considering only cantilever geometry and do not take into account properties of any object or substance attached to the cantilever. Neglecting the influence of the colloidal sphere on the cantilever characteristics introduces significant uncertainty in a spring constant determination and affects all further considerations. In this work we propose a new method of spring constant calibration for 'colloidal probe' type cantilevers based on the direct measurement of force constant. The Optical Tweezers based calibration method will help to increase the accuracy and repeatability of the AFM colloidal probe experiments.

Physiologically Relevant Mechanics of Biodegradable Polyester Nanoparticles

Despite the extensive use of biodegradable polyester nanoparticles for drug delivery, and reports of the strong influence of nanoparticle mechanics on nano-bio interactions, there is a lack of systematic studies on the mechanics of these nanoparticles under physiologically relevant conditions. Here, we report indentation experiments on poly(lactic acid) and poly(lactide-co-glycolide) nanoparticles using atomic force microscopy. While dried nanoparticles were found to be rigid at room temperature, their elastic modulus was found to decrease by as much as 30 fold under simulated physiological conditions (i.e., in water at 37 °C). Differential scanning calorimetry confirms that this softening can be attributed to the glass transition of the nanoparticles. Using a combination of mechanical and thermoanalytical characterization, the plasticizing effects of miniaturization, molecular weight, and immersion in water were investigated. Collectively, these experiments provide insight for experimentalists exploring the relationship between polymer nanoparticle mechanics and in vivo behavior.

Molecular regulation of TLR signaling in health and disease: mechano-regulation of macrophages and TLR signaling

Immune cells encounter tissues with vastly different biochemical and physical characteristics. Much of the research emphasis has focused on the role of cytokines and chemokines in regulating immune cell function, but the role of the physical microenvironment has received considerably less attention. The tissue mechanics, or stiffness, of healthy tissues varies dramatically from soft adipose tissue and brain to stiff cartilage and bone. Tissue mechanics also change due to fibrosis and with diseases such as atherosclerosis or cancer. The process by which cells sense and respond to their physical microenvironment is called mechanotransduction. Here we review mechanotransduction in immunologically important diseases and how physical characteristics of tissues regulate immune cell function, with a specific emphasis on mechanoregulation of macrophages and TLR signaling.

Lamellar liquid crystals maintain keratinocytes' membrane fluidity: An AFM qualitative and quantitative study

Despite extensive investigations of lamellar liquid crystals for dermal application, the effects of these systems at the cellular level are still not well elucidated. The key aim of this study was to determine the elasticity and morphological features of keratinocytes after exposure to a lamellar liquid crystal system (LLCS) using atomic force microscopy (AFM) as the method of choice. Prior to AFM assessment, a cell proliferation test and light plus fluorescence imaging were applied to determine the sub-toxic concentration of LLCS. According to the AFM results, slightly altered morphology was observed in the case of fixed keratinocytes, while an intact morphology was visualized on live cells. From the quantitative study, decreased Young's moduli were determined for fixed cells (i.e., 8.6 vs. 15.2 MPa and 1.3 vs. 2.9 MPa for ethanol or PFA-fixed LLCS-treated vs. control cells, respectively) and live cells (i.e., ranging from 0.6 to 2.8 for LLCS-treated vs. 1.1-4.5 MPa for untreated cells), clearly demonstrating increased cell elasticity. This is related to improved membrane fluidity as a consequence of interactions between the acyl chains of cell membrane phosphatidylcholine and those of LLCS. What seems to be of major importance is that the study confirms the potential clinical relevance of such systems in treatment of aged skin with characteristically more rigid epithelial cells.

Sialylation status and mechanical properties of THP-1 macrophages upon LPS stimulation

Cell surface receptors are the key contributors of macrophage function. Most macrophage cell surface receptors are glycoproteins with sialic acids at the terminal of their glycans. It is well recognized that lipopolysaccharide (LPS) induces cell surface sialylation changes that may in turn contribute to macrophage functions. In addition, cellular mechanics such as elasticity is also a major determinant of macrophage function, which in turn is modulated by LPS. In this report, we characterized the sialylation status of macrophages upon LPS stimulation and assessed the changes in its mechanical properties and function. Specifically, we confirmed that sialylation status is closely related to macrophage biomechanical characteristics (elastic modulus, tether force, tether radius, adhesion force, and membrane tension) and thus directly involved in macrophage function. Further, we modulated macrophage sialylation status by feeding the cell with exogenous free sialic acid (Neu5Ac, Neu5Gc) and sialidase inhibitors, and examined the resulting effects on cellular mechanics and function. A systematic recognition of sialylation status related to cellular mechanics of macrophages will contribute to defining their phenotypes and elucidate macrophage functional diversity.

Combination of inductive effect of lipopolysaccharide and in situ mechanical conditioning for forming an autologous vascular graft in vivo

Autologous vascular grafts have the advantages of better biocompatibility and prognosis. However, previous studies that implanted bare polymer tubes in animals to grow autologous tubular tissues were limited by their poor yield rates and stability. To enhance the yield rate of the tubular tissue, we employed a design with the addition of overlaid autologous whole blood scaffold containing lipopolysaccharides (LPS). Furthermore, we applied in vivo dynamic mechanical stimuli through cyclically inflatable silicone tube to improve the mechanical properties of the harvested tissues. The effectiveness of the modification was examined by implanting the tubes in the peritoneal cavity of rats. A group without mechanical stimuli served as the controls. After 24 days of culture including 16 days of cyclic mechanical stimuli, we harvested the tubular tissue forming on the silicone tube for analysis or further autologous interposition vascular grafting. In comparison with those without cyclic dynamic stimuli, tubular tissues with this treatment during in vivo culture had stronger mechanical properties, better smooth muscle differentiation, and more collagen and elastin expression by the end of incubation period in the peritoneal cavity. The grafts remained patent after 4 months of implantation and showed the presence of endothelial and smooth muscle cells. This model shows a new prospect for vascular tissue engineering.

Acoustic tweezing cytometry for mechanical phenotyping of macrophages and mechanopharmaceutical cytotripsy

Macrophages are immune cells responsible for tissue debridement and fighting infection. Clofazimine, an FDA-approved antibiotic, accumulates and precipitates as rod-shaped, crystal-like drug inclusions within macrophage lysosomes. Drug treatment as well as pathophysiological states could induce changes in macrophage mechanical property which in turn impact their phenotype and function. Here we report the use of acoustic tweezing cytometry as a new approach for in situ mechanical phenotyping of macrophages and for targeted macrophage cytotripsy. Acoustic tweezing cytometry applies ultrasound pulses to exert controlled forces to individual cells via integrin-bound microbubbles, enabling a creep test for measuring cellular mechanical property or inducing irreversible changes to the cells. Our results revealed that macrophages with crystal-like drug inclusions became significantly softer with higher cell compliance, and behaved more elastic with faster creep and recovery time constants. On the contrary, phagocytosis of solid polyethylene microbeads or treatment with soluble clofazimine rendered macrophages stiffer. Most notably, application of ultrasound pulses of longer duration and higher amplitude in ATC actuated the integrin-bound microbubbles to mobilize the crystal-like drug inclusions inside macrophages, turning the rod-shaped drug inclusions into intracellular microblender that effectively destructed the cells. This phenomenon of acoustic mechanopharmaceutical cytotripsy may be exploited for ultrasound activated, macrophage-directed drug release and delivery.

Inhibition of inflammatory response in human keratinocytes by magnetic nanoparticles functionalized with PBP10 peptide derived from the PIP2-binding site of human plasma gelsolin

Background

Human plasma gelsolin (pGSN) is a multifunctional actin-binding protein involved in a variety of biological processes, including neutralization of pro-inflammatory molecules such as lipopolysaccharide (LPS) and lipoteichoic acid (LTA) and modulation of host inflammatory response. It was found that PBP10, a synthetic rhodamine B-conjugated peptide, based on the phosphoinositide-binding site of pGSN, exerts bactericidal activity against Gram-positive and Gram-negative bacteria, interacts specifically with LPS and LTA, and limits microbial-induced inflammatory effects. The therapeutic efficiency of PBP10 when immobilized on the surface of iron oxide-based magnetic nanoparticles was not evaluated, to date.

Results

Using the human keratinocyte cell line HaCaT stimulated by bacterially-derived LPS and LTA as an in vitro model of bacterial infection, we examined the anti-inflammatory effects of nanosystems consisting of iron oxide-based magnetic nanoparticles with aminosilane (MNP@NH₂) or gold shells (MNP@Au) functionalized by a set of peptides, derived from the phosphatidylinositol 4,5-bisphosphate (PIP2)-binding site of the human plasma protein gelsolin, which also binds LPS and LTA. Our results indicate that these nanosystems can kill both Gram-positive and Gram-negative bacteria and limit the production of inflammatory mediators, including nitric oxide (NO), reactive oxygen species (ROS), and interleukin-8 (IL-8) in the response to heat-killed microbes or extracted bacterial cell wall components. The nanoparticles possess the potential to improve therapeutic efficacy and are characterized by lower toxicity and improved hemocompatibility when compared to free peptides. Atomic force microscopy (AFM) showed that these PBP10-based nanosystems prevented changes in nanomechanical properties of cells that were otherwise stimulated by LPS.

Conclusions

Neutralization of endotoxemia-mediated cellular effects by gelsolin-derived peptides and PBP10-containing nanosystems might be considered as potent therapeutic agents in the improved therapy of bacterial infections and microbial-induced inflammation.

Escherichia coli lipopolysaccharide induces alveolar epithelial cell stiffening

INTRODUCTION

Application of lipopolysaccharide (LPS) is a widely employed model to mimic acute respiratory distress syndrome (ARDS). Available data regarding LPS-induced biomechanical changes on pulmonary epithelial cells are limited only to P. aeruginosa LPS. Considering that LPS from different bacteria could promote a specific mechanical response in epithelial cells, we aim to assess the effect of E. coli LPS, widely employed as a model of ARDS, in the biomechanics of alveolar epithelial cells.

METHODS

Young's modulus (E) of alveolar epithelial cells (A549) was measured by atomic force microscopy every 5 min throughout 60 min of experiment after treatment with LPS from E. coli (100 μg/mL). The percentage of cells presenting actin stress fibers (F-actin staining) was also evaluated. Control cells were treated with culture medium and the values obtained were compared with LPS-treated cells for each time-point.

RESULTS

Application of LPS induced significant increase in E after 20 min (77%) till 60 min (104%) in comparison to controls. Increase in lung epithelial cell stiffness induced by LPS was associated with a higher number of cells presenting cytoskeletal remodeling.

CONCLUSIONS

The observed effects of E. coli LPS on alveolar epithelial cells suggest that this widely-used LPS is able to promote a quick formation of actin stress fibers and stiffening cells, thereby facilitating the disruption of the pulmonary epithelial barrier.

Characterization of Cell Scaffolds by Atomic Force Microscopy

This review reports on the use of the atomic force microscopy (AFM) in the investigation of cell scaffolds in recent years. It is shown how the technique is able to deliver information about the scaffold surface properties (e.g., topography), as well as about its mechanical behavior (Young's modulus, viscosity, and adhesion). In addition, this short review also points out the utilization of the atomic force microscope technique beyond its usual employment in order to investigate another type of basic questions related to materials physics, chemistry, and biology. The final section discusses in detail the novel uses that those alternative measuring modes can bring to this field in the future.

Cholesterol Regulates Monocyte Rolling through CD44 Distribution

Cholesterol is an important risk factor of atherosclerosis, due to its active uptake by monocytes/macrophages. Monocyte recruitment from flowing blood to atherosclerotic foci is the key first step in the development of atherosclerosis. Cholesterol content alters cell membrane stiffness, and lateral lipid and protein diffusion. We hypothesized that cholesterol content will modulate the recruitment of monocytes to inflamed endothelial surface by altering the dynamics of adhesion receptors. We depleted or enriched the cellular cholesterol levels using methyl-β-cyclodextran in freshly isolated human monocytes. We investigated the effect of these changes on the mechanics of monocyte rolling on E-selectin surfaces at 1 dyn/cm² in microchannels. Using imaging flow cytometry and atomic force microscopy, we characterized the distribution of lipid rafts and the E-selectin counterreceptor CD44 on the monocyte surface. We observed that lower levels of cholesterol resulted in the uniform, CD44-mediated rolling of monocytes on the E-selectin-coated surfaces. We also observed that cells depleted of cholesterol had higher membrane fluidity, and more uniform distribution of CD44 counterreceptor, which resulted in smooth motion of the cells compared to cells enriched with cholesterol. This work demonstrates that cholesterol can modulate monocyte adhesion by regulating the receptor mobility, and our results provide insights into the biophysical regulation of inflammation for the better understanding of diseases like atherosclerosis and hypercholesterolemia.

Harvesting pre-polarized macrophages using thermo-responsive substrates

In the cell culture environment macrophages are highly adherent cells. Currently used methods to harvest macrophages have the disadvantage of reducing cell viability and their ability to re-attach after seeding. Although thermo-responsive surfaces have been employed to harvest cell sheets no reports are available to use these to harvest (pre-polarized) macrophages. We show that this method significantly improves the yield of living macrophages and percentage of subsequent cell reattachment, whilst having a minimal effect on the cell phenotype.

The selective cytotoxicity of DSF-Cu attributes to the biomechanical properties and cytoskeleton rearrangements in the normal and cancerous nasopharyngeal epithelial cells

Cancer initiation and progression follow complex changes of cellular architecture and biomechanical property. Cancer cells with more submissive (or "softer") than their healthy counterparts attributed to the reorganization of the complex cytoskeleton structure, may be considered as a potential anti-tumor therapeutic target. In this study, atomic force microscopy (AFM) was carried out to detect the topographical and biophysical changes of nasopharyngeal carcinoma CNE-2Z cells and normal nasopharyngeal epithelial cells NP69-SV40T by treating the Disulfiram chelated with Cu²⁺ (DSF-Cu). DSF-Cu induced the apoptotic population, ROS production and decreased the NF-κB-p65 expression of CNE-2Z cells, which was much higher than those of NP69-SV40T cells. DSF-Cu caused the obvious changes of cell morphology and membrane ultrastructure in CNE-2Z cells. The roughness decreased and stiffness increased significantly in CNE-2Z cells, which correlated with the rearrangement of intracellular F-actin, FLNa and α-tubulin structures in CNE-2Z cells. And the adhesion force of CNE-2Z cells was also increased accompanied with the increased E-cadherin expression. However, these results could not be observed in the NP69-SV40T cells even the concentration of DSF reached up to 400nM. Finally, the detection of cell wound scratch assay confirmed DSF-Cu could inhibit the migration of CNE-2Z cells, but no effect on NP69-SV40T cells. These findings demonstrated the selective cytotoxicity of DSF-Cu in CNE-2Z cells may attribute to the different mechanical properties and cytoskeleton rearrangement from the normal nasopharyngeal epithelial cells.

Immunomodulatory effects of polysaccharide compounds in macrophages revealed by high resolution AFM

Polysaccharide compounds (PCs), which composed of different kinds of polysaccharides always isolated from different kinds of traditional Chinese medicine, are now attracting more and more attentions due to their strong immunomodulatory activities beyond the corresponding one-component polysaccharides. In this study, we demonstrated for the first time that PCs-1 and PCs-2 had strong immunomodulatory effects on macrophages both in in vitro and in vivo models by atomic force microscopy (AFM). By high resolution AFM imaging, PCs-1 and PCs-2 were found to inhibit LPS induced cell surface particle size and roughness increase in RAW264.7 macrophages, demonstrating the anti-inflammatory effects of PCs-1 and PCs-2 on macrophages. PCs-1 and PCs-2 were also proved to increase the particle size and roughness of resting RAW264.7 macrophages, which suggested that PCs could activate resting RAW264.7 macrophages. And additionally, PCs-1 and PCs-2 were also found to reverse the surface particle size and roughness decrease of peritoneal macrophages isolated from cyclophosphamide induced immunosuppressive mice, suggesting the activation effects of PCs-1 and PCs-2 on immunosuppressive macrophages. These results further enhanced our understanding of macrophage activations by direct imaging of cell surface ultrastructure and also highlighted AFM as a novel nanotool for macrophage detections. And most importantly, these results also indicated the outstanding immunomodulatory effects of PCs on macrophages, which therefore suggested that PCs could be served as a kind of novel immunomodulatory agents that would benefit human health. SCANNING 38:792-801, 2016. © 2016 Wiley Periodicals, Inc.

Investigating cell-substrate and cell-cell interactions by means of single-cell-probe force spectroscopy

Cell adhesion forces are typically a mixture of specific and nonspecific cell-substrate and cell-cell interactions. In order to resolve these phenomena, Atomic Force Microscopy appears as a powerful device which can measure cell parameters by means of manipulation of single cells. This method, commonly known as cell-probe force spectroscopy, allows us to control the force applied, the area of interest, the approach/retracting speed, the force rate, and the time of interaction. Here, we developed a novel approach for in situ cantilever cell capturing and measurement of specific cell interactions. In particular, we present a new setup consisting of two different half-surfaces coated either with recrystallized SbpA bacterial cell surface layer proteins (S-layers) or integrin binding Fibronectin, on which MCF-7 breast cancer cells are incubated. The presence of a clear physical boundary between both surfaces benefits for a quick detection of the region under analysis. Thus, quantitative results about SbpA-cell and Fibronectin-cell adhesion forces as a function of the contact time are described. Additionally, the importance of the cell spreading in cell-cell interactions has been studied for surfaces coated with two different Fibronectin concentrations: 20 μg/mL (FN20) and 100 μg/mL (FN100), which impact the number of substrate receptors. Microsc. Res. Tech. 80:124-130, 2017. © 2016 Wiley Periodicals, Inc.

Investigation of quercetin-induced HepG2 cell apoptosis-associated cellular biophysical alterations by atomic force microscopy

Quercetin, a wildly distributed bioflavonoid, has been proved to possess excellent antitumor activity on hepatocellular carcinoma (HCC). In the present study, the biophysical properties of HepG2 cells were qualitatively and quantitatively determined using high resolution atomic force microscopy (AFM) to understand the anticancer effects of quercetin on HCC cells at nanoscale. The results showed that quercetin could induce severe apoptosis in HepG2 cells through arrest of cell cycle and disruption of mitochondria membrane potential. Additionally, the nuclei and F-actin structures of HepG2 cells were destroyed by quercetin treatment as well. AFM morphological data showed some typical apoptotic characterization of HepG2 cells with increased particle size and roughness in the ultrastructure of cell surface upon quercetin treatment. As an important biophysical property of cells, the membrane stiffness of HepG2 cells was further quantified by AFM force measurements, which indicated that HepG2 cells became much stiffer after quercetin treatment. These results collectively suggest that quercetin can be served as a potential therapeutic agent for HCC, which not only extends our understanding of the anticancer effects of quercetin against HCC cells into nanoscale, but also highlights the applications of AFM for the investigation of anticancer drugs.

Quantifying cellular mechanics and adhesion in renal tubular injury using single cell force spectroscopy

Tubulointerstitial fibrosis represents the major underlying pathology of diabetic nephropathy where loss of cell-to-cell adhesion is a critical step. To date, research has predominantly focussed on the loss of cell surface molecular binding events that include altered protein ligation. In the current study, atomic force microscopy single cell force spectroscopy (AFM-SCFS) was used to quantify changes in cellular stiffness and cell adhesion in TGF-β1 treated kidney cells of the human proximal tubule (HK2). AFM indentation of TGF-β1 treated HK2 cells showed a significant increase (42%) in the elastic modulus (stiffness) compared to control. Fluorescence microscopy confirmed that increased cell stiffness is accompanied by reorganization of the cytoskeleton. The corresponding changes in stiffness, due to F-actin rearrangement, affected the work of detachment by changing the separation distance between two adherent cells. Overall, our novel data quantitatively demonstrate a correlation between cellular elasticity, adhesion and early morphologic/phenotypic changes associated with tubular injury.

FROM THE CLINICAL EDITOR

Diabetes affects many patients worldwide. One of the long term problems is diabetic nephropathy. Here, the authors utilized atomic force microscopy single cell force spectroscopy (AFM- SCFS) to study cellular stiffness and cell adhesion after TGF1 treatment in human proximal tubule kidney cells. The findings would help further understand the overall disease mechanism in diabetic patients.

Qualitative and Quantitative Analysis of ROS-Mediated Oridonin-Induced Oesophageal Cancer KYSE-150 Cell Apoptosis by Atomic Force Microscopy

High levels of intracellular reactive oxygen species (ROS) in cells is recognized as one of the major causes of cancer cell apoptosis and has been developed into a promising therapeutic strategy for cancer therapy. However, whether apoptosis associated biophysical properties of cancer cells are related to intracellular ROS functions is still unclear. Here, for the first time, we determined the changes of biophysical properties associated with the ROS-mediated oesophageal cancer KYSE-150 cell apoptosis using high resolution atomic force microscopy (AFM). Oridonin was proved to induce ROS-mediated KYSE-150 cell apoptosis in a dose dependent manner, which could be reversed by N-acetylcysteine (NAC) pretreatment. Based on AFM imaging, the morphological damage and ultrastructural changes of KYSE-150 cells were found to be closely associated with ROS-mediated oridonin-induced KYSE-150 cell apoptosis. The changes of cell stiffness determined by AFM force measurement also demonstrated ROS-dependent changes in oridonin induced KYSE-150 cell apoptosis. Our findings not only provided new insights into the anticancer effects of oridonin, but also highlighted the use of AFM as a qualitative and quantitative nanotool to detect ROS-mediated cancer cell apoptosis based on cell biophysical properties, providing novel information of the roles of ROS in cancer cell apoptosis at nanoscale.

Effects of temperature and cellular interactions on the mechanics and morphology of human cancer cells investigated by atomic force microscopy

Cell mechanics plays an important role in cellular physiological activities. Recent studies have shown that cellular mechanical properties are novel biomarkers for indicating the cell states. In this article, temperature-controllable atomic force microscopy (AFM) was applied to quantitatively investigate the effects of temperature and cellular interactions on the mechanics and morphology of human cancer cells. First, AFM indenting experiments were performed on six types of human cells to investigate the changes of cellular Young's modulus at different temperatures and the results showed that the mechanical responses to the changes of temperature were variable for different types of cancer cells. Second, AFM imaging experiments were performed to observe the morphological changes in living cells at different temperatures and the results showed the significant changes of cell morphology caused by the alterations of temperature. Finally, by co-culturing human cancer cells with human immune cells, the mechanical and morphological changes in cancer cells were investigated. The results showed that the co-culture of cancer cells and immune cells could cause the distinct mechanical changes in cancer cells, but no significant morphological differences were observed. The experimental results improved our understanding of the effects of temperature and cellular interactions on the mechanics and morphology of cancer cells.

The Cardiomyopathy Lamin A/C D192G Mutation Disrupts Whole-Cell Biomechanics in Cardiomyocytes as Measured by Atomic Force Microscopy Loading-Unloading Curve Analysis

Atomic force microscopy (AFM) cell loading/unloading curves were used to provide comprehensive insights into biomechanical behavior of cardiomyocytes carrying the lamin A/C (LMNA) D192G mutation known to cause defective nuclear wall, myopathy and severe cardiomyopathy. Our results suggested that the LMNA D192G mutation increased maximum nuclear deformation load, nuclear stiffness and fragility as compared to controls. Furthermore, there seems to be a connection between this lamin nuclear mutation and cell adhesion behavior since LMNA D192G cardiomyocytes displayed loss of AFM probe-to-cell membrane adhesion. We believe that this loss of adhesion involves the cytoskeletal architecture since our microscopic analyses highlighted that mutant LMNA may also lead to a morphological alteration in the cytoskeleton. Furthermore, chemical disruption of the actin cytoskeleton by cytochalasin D in control cardiomyocytes mirrored the alterations in the mechanical properties seen in mutant cells, suggesting a defect in the connection between the nucleoskeleton, cytoskeleton and cell adhesion molecules in cells expressing the mutant protein. These data add to our understanding of potential mechanisms responsible for this fatal cardiomyopathy, and show that the biomechanical effects of mutant lamin extend beyond nuclear mechanics to include interference of whole-cell biomechanical properties.

Physical and mechanical regulation of macrophage phenotype and function

Macrophages are tissue-resident immune cells that play a critical role in maintaining homeostasis and fighting infection. In addition, these cells are involved in the progression of many pathologies including cancer and atherosclerosis. In response to a variety of microenvironmental stimuli, macrophages can be polarized to achieve a spectrum of functional phenotypes. This review will discuss some emerging evidence in support of macrophage phenotypic regulation by physical and mechanical cues. As alterations in the physical microenvironment often underlie pathophysiological states, an understanding of their effects on macrophage phenotype and function may help provide mechanistic insights into disease pathogenesis.

Nanoscale imaging and mechanical analysis of Fc receptor-mediated macrophage phagocytosis against cancer cells

Fc receptor-mediated macrophage phagocytosis against cancer cells is an important mechanism in the immune therapy of cancers. Traditional research about macrophage phagocytosis was based on optical microscopy, which cannot reveal detailed information because of the 200-nm-resolution limit. Quantitatively investigating the macrophage phagocytosis at micro- and nanoscale levels is still scarce. The advent of atomic force microscopy (AFM) offers an excellent analytical instrument for quantitatively investigating the biological processes at single-cell and single-molecule levels under native conditions. In this work, we combined AFM and fluorescence microscopy to visualize and quantify the detailed changes in cell morphology and mechanical properties during the process of Fc receptor-mediated macrophage phagocytosis against cancer cells. Lymphoma cells were discernible by fluorescence staining. Then, the dynamic process of phagocytosis was observed by time-lapse optical microscopy. Next, AFM was applied to investigate the detailed cellular behaviors during macrophage phagocytosis under the guidance of fluorescence recognition. AFM imaging revealed the distinct features in cellular ultramicrostructures for the different steps of macrophage phagocytosis. AFM cell mechanical property measurements indicated that the binding of cancer cells to macrophages could make macrophages become stiffer. The experimental results provide novel insights in understanding the Fc-receptor-mediated macrophage phagocytosis.

The effect of the endothelial cell cortex on atomic force microscopy measurements

We examined whether the presence of the cell cortex might explain, in part, why previous studies using atomic force microscopy (AFM) to measure cell modulus (E) gave higher values with sharp tips than for larger spherical tips. We confirmed these AFM findings in human umbilical vein endothelial cells (HUVEC) and Schlemm's canal (SC) endothelial cells with AFM indentation ≤ 400 nm, two cell types with prominent cortices (312 ± 65 nm in HUVEC and 371 ± 91 nm in SC cells). With spherical tips, E (kPa) was 0.71 ± 0.16 in HUVEC and 0.94 ± 0.06 in SC cells. Much higher values of E were measured using sharp tips: 3.23 ± 0.54 in HUVEC and 6.67 ± 1.07 in SC cells. Previous explanations for this difference such as strain hardening or a substrate effect were shown to be inconsistent with our measurements. Finite element modeling studies showed that a stiff cell cortex could explain the results. In both cell types, Latrunculin-A greatly reduced E for sharp and rounded tips, and also reduced the ratio of the values measured with a sharp tip as compared to a rounded tip. Our results suggest that the cell cortex increases the apparent endothelial cell modulus considerably when measured using a sharp AFM tip.

Membrane elastic properties and cell function

Recent studies indicate that the cell membrane, interacting with its attached cytoskeleton, is an important regulator of cell function, exerting and responding to forces. We investigate this relationship by looking for connections between cell membrane elastic properties, especially surface tension and bending modulus, and cell function. Those properties are measured by pulling tethers from the cell membrane with optical tweezers. Their values are determined for all major cell types of the central nervous system, as well as for macrophage. Astrocytes and glioblastoma cells, which are considerably more dynamic than neurons, have substantially larger surface tensions. Resting microglia, which continually scan their environment through motility and protrusions, have the highest elastic constants, with values similar to those for resting macrophage. For both microglia and macrophage, we find a sharp softening of bending modulus between their resting and activated forms, which is very advantageous for their acquisition of phagocytic functions upon activation. We also determine the elastic constants of pure cell membrane, with no attached cytoskeleton. For all cell types, the presence of F-actin within tethers, contrary to conventional wisdom, is confirmed. Our findings suggest the existence of a close connection between membrane elastic constants and cell function.

In situ hydrodynamic lateral force calibration of AFM colloidal probes

Lateral force microscopy (LFM) is an application of atomic force microscopy (AFM) to sense lateral forces applied to the AFM probe tip. Recent advances in tissue engineering and functional biomaterials have shown a need for the surface characterization of their material and biochemical properties under the application of lateral forces. LFM equipped with colloidal probes of well-defined tip geometries has been a natural fit to address these needs but has remained limited to provide primarily qualitative results. For quantitative measurements, LFM requires the successful determination of the lateral force or torque conversion factor of the probe. Usually, force calibration results obtained in air are used for force measurements in liquids, but refractive index differences between air and liquids induce changes in the conversion factor. Furthermore, in the case of biochemically functionalized tips, damage can occur during calibration because tip-surface contact is inevitable in most calibration methods. Therefore, a nondestructive in situ lateral force calibration is desirable for LFM applications in liquids. Here we present an in situ hydrodynamic lateral force calibration method for AFM colloidal probes. In this method, the laterally scanned substrate surface generated a creeping Couette flow, which deformed the probe under torsion. The spherical geometry of the tip enabled the calculation of tip drag forces, and the lateral torque conversion factor was calibrated from the lateral voltage change and estimated torque. Comparisons with lateral force calibrations performed in air show that the hydrodynamic lateral force calibration method enables quantitative lateral force measurements in liquid using colloidal probes.

Real-time monitoring of cell elasticity reveals oscillating myosin activity

The cytoskeleton is the physical and biochemical interface for a large variety of cellular processes. Its complex regulation machinery is involved upstream and downstream in various signaling pathways. The cytoskeleton determines the mechanical properties of a cell. Thus, cell elasticity could serve as a parameter reflecting the behavior of the system rather than reflecting the specific properties of isolated components. In this study, we used atomic force microscopy to perform real-time monitoring of cell elasticity unveiling cytoskeletal dynamics of living bronchial epithelial cells. In resting cells, we found a periodic activity of the cytoskeleton. Amplitude and frequency of this spontaneous oscillation were strongly affected by intracellular calcium. Experiments reveal that basal cell elasticity and superimposed elasticity oscillations are caused by the collective action of myosin motor proteins. We characterized the cell as a mechanically multilayered structure, and followed cytoskeletal dynamics in the different layers with high time resolution. In conclusion, the collective activities of the myosin motor proteins define overall mechanical cell dynamics, reflecting specific changes of the chemical and mechanical environment.

Forcing form and function: biomechanical regulation of tumor evolution

Cancer cells exist in a constantly evolving tissue microenvironment of diverse cell types within a proteinaceous extracellular matrix. As tumors evolve, the physical forces within this complex microenvironment change, with pleiotropic effects on both cell- and tissue-level behaviors. Recent work suggests that these biomechanical factors direct tissue development and modulate tissue homeostasis, and, when altered, crucially influence tumor evolution. In this review, we discuss the biomechanical regulation of cell and tissue homeostasis from the molecular, cellular and tissue levels, including how modifications of this physical dialogue could contribute to cancer etiology. Because of the broad impact of biomechanical factors on cell and tissue functions, an understanding of tumor evolution from the biomechanical perspective should improve risk assessment, clinical diagnosis and the efficacy of cancer treatment.

Modeling receptor-mediated endocytosis of polymer-functionalized iron oxide nanoparticles by human macrophages

Although systemically applied nanoparticles are quickly taken up by phagocytic cells, mainly macrophages, the interactions between engineered nanoparticles and macrophages are still not well defined. We therefore analyzed the uptake of diagnostically used carboxydextran-coated superparamagnetic iron oxide nanoparticles of 60 nm (SPIO) and 20 nm (USPIO) by human macrophages. By pharmacological and in vitro knockdown approaches, the principal uptake mechanism for both particles was identified as clathrin-mediated, scavenger receptor A-dependent endocytosis. We developed a mathematical model of the uptake process that allows determination of key parameters of endocytosis, including the rate of uptake, the number of nanoparticles per cell in saturation, the mean uptake time, and the correlation between the number of internalized nanoparticles and their extracellular concentration. The calculated parameters correlate well with experimental data obtained by confocal microscopy. Moreover, the model predicts the individual and collective wrapping times of different nanoparticles, describes the relation between cytoskeletal forces, membrane elasticity and the uptake time. We also introduced a new physical parameter 'a' governing the collective uptake process, a reflecting minimal linear spacing between simultaneously acting neighboring endocytotic pits.

Biomechanical and proteomic analysis of INF- beta-treated astrocytes

Astrocytes have a key role in the pathogenesis of several diseases including multiple sclerosis and were proposed as the designed target for immunotherapy. In this study we used atomic force microscopy (AFM) and proteomics methods to analyse and correlate the modifications induced in the viscoleastic properties of astrocytes to the changes induced in protein expression after interferon- beta (IFN-beta) treatment. Our results indicated that IFN-beta treatment resulted in a significant decrease in the Young's modulus, a measure of cell elasticity, in comparison with control cells. The molecular mechanisms that trigger these changes were investigated by 2DE (two-dimensional electrophoresis) and confocal analyses and confirmed by western blotting. Altered proteins were found to be involved in cytoskeleton organization and other important physiological processes.

Cytomechanical and topological investigation of MCF-7 cells by scanning force microscopy

Despite enormous advances in breast cancer biology, there is an increased demand for new technologies/methods that are able to provide supplementary information to genomics and proteomics. Here, we exploit scanning force microscopy (SFM) in combination with confocal microscopy, to investigate the morphological and mechanical properties of two neoplastic cell lines: (i) MCF-7 (human breast cancer) and (ii) HeLa (human cervical carcinoma). Living and fixed cells either in phosphate buffer solution (PBS) or in air have been studied, and the viscoelastic properties (including the Young's modulus) of cells grown onto standard and modified (e.g. by fibronectin, one of the cellular matrix components) substrates have been measured. We observed different Young's modulus values, influenced by the adhesion and growth behaviour onto specific substrate surfaces.