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Collective cell migration is an essential process throughout the lives of multicellular organisms, for example in embryonic development, wound healing and tumour metastasis. Substrates or interfaces associated with these processes are typically curved, with radii of curvature comparable to many cell lengths. Using both artificial geometries and lung alveolospheres derived from human induced pluripotent stem cells, here we show that cells sense multicellular-scale curvature and that it plays a role in regulating collective cell migration. As the curvature of a monolayer increases, cells reduce their collectivity and the multicellular flow field becomes more dynamic. Furthermore, hexagonally shaped cells tend to aggregate in solid-like clusters surrounded by non-hexagonal cells that act as a background fluid. We propose that cells naturally form hexagonally organized clusters to minimize free energy, and the size of these clusters is limited by a bending energy penalty. We observe that cluster size grows linearly as sphere radius increases, which further stabilizes the multicellular flow field and increases cell collectivity. As a result, increasing curvature tends to promote the fluidity in multicellular monolayer. Together, these findings highlight the potential for a fundamental role of curvature in regulating both spatial and temporal characteristics of three-dimensional multicellular systems.

Based on density functional theory and Debye quasi-harmonic approximation, the effects of high pressure on the phonon, electronic, elastic, and thermodynamic properties of the orthogonal phase HfSi2 have been calculated. The calculated results show that when the pressure is within the pressure range of 0 GPa to 50 GPa, HfSi2 is dynamically stable, and there is no virtual frequency on the phonon spectrum, but when the pressure is greater than 70 GPa, virtual frequencies appear near the phonon spectrum X, A structural phase change occurred. We predict that the band structure of HfSi2 is metallic. As the pressure increases, the elastic constant Cij increases and conforms to the Born criterion. It is mechanically stable in a certain pressure range. At the same time, B, E, G, and B/G all increase with the increase of pressure. This shows that changing the pressure appropriately can change the ductility and toughness of the material. The Debye temperature and sound velocity increase linearly with the increase of pressure, so the elasticity, hardness, melting point, and specific heat of the material can be improved by pressure.

Apoptosis exists ubiquitously in organisms and plays an essential role in maintaining the homeostasis of functional tissues. While the signaling pathway of cell apoptosis has been widely studied, the mechanism of how apoptotic cells regulate the structural homeostasis of a living tissue still remains largely elusive. Using a functional epithelial monolayer as a model system, we find that the integrity of the epithelium is interrupted by apoptosis-induced defects, with an increasing permeability to small molecules across the epithelium. The defects promote a structural reorganization through enhanced cell spreading and migratory dynamics, resulting in a quick recovery of epithelium integrity. Moreover, we show the epithelial monolayer remodeling is driven by local enhanced traction force after apoptosis, which triggers the process of fluidization and mesenchymal-like migration. Our results show the quick recovery of epithelial homeostasis when being interrupted by cell apoptosis, and indicate the importance of apoptosis-induced mechanical force in mediating cell behaviors to maintain the structural integrity of epithelium.

Sustained proliferation is a significant driver of cancer progression. Cell-cycle advancement is coupled with cell size, but it remains unclear how multiple cells interact to control their volume in 3D clusters. In this study, we propose a mechano-osmotic model to investigate the evolution of volume dynamics within multicellular systems. Volume control depends on an interplay between multiple cellular constituents, including gap junctions, mechanosensitive ion channels, energy-consuming ion pumps, and the actomyosin cortex, that coordinate to manipulate cellular osmolarity. In connected cells, we show that mechanical loading leads to the emergence of osmotic pressure gradients between cells with consequent increases in cellular ion concentrations driving swelling. We identify how gap junctions can amplify spatial variations in cell volume within multicellular spheroids and, further, describe how the process depends on proliferation-induced solid stress. Our model may provide new insight into the role of gap junctions in breast cancer progression., Cell proliferation is regulated by cell volume, but it is unclear how individual cancer cells coordinate to regulate cell volumes in 3D clusters. Here the authors propose a mechano-osmotic model to analyse the exchange of fluid and ions between connected cells and their environment in response to proliferation-induced solid stress.

The ability of a cell to regulate its mechanical properties is central to its function. Emerging evidence suggests that interactions between the cell nucleus and cytoskeleton influence cell mechanics through poorly understood mechanisms. Here we conduct quantitative confocal imaging to show that the loss of A-type lamins tends to increase nuclear and cellular volume while the loss of B-type lamins behaves in the opposite manner. We use fluorescence recovery after photobleaching, atomic force microscopy, optical tweezer microrheology, and traction force microscopy to demonstrate that A-type lamins engage with both F-actin and vimentin intermediate filaments (VIFs) through the linker of nucleoskeleton and cytoskeleton (LINC) complexes to modulate cortical and cytoplasmic stiffness as well as cellular contractility in mouse embryonic fibroblasts (MEFs). In contrast, we show that B-type lamins predominantly interact with VIFs through LINC complexes to regulate cytoplasmic stiffness and contractility. We then propose a physical model mediated by the lamin–LINC complex that explains these distinct mechanical phenotypes (mechanophenotypes). To verify this model, we use dominant negative constructs and RNA interference to disrupt the LINC complexes that facilitate the interaction of the nucleus with the F-actin and VIF cytoskeletons and show that the loss of these elements results in mechanophenotypes like those observed in MEFs that lack A- or B-type lamin isoforms. Finally, we demonstrate that the loss of each lamin isoform softens the cell nucleus and enhances constricted cell migration but in turn increases migration-induced DNA damage. Together, our findings uncover distinctive roles for each of the four major lamin isoforms in maintaining nucleocytoskeletal interactions and cellular mechanics.

Summary It is well established that the early malignant tumor invades surrounding extracellular matrix (ECM) in a manner that depends upon material properties of constituent cells, surrounding ECM, and their interactions. Recent studies have established the capacity of the invading tumor spheroids to evolve into coexistent solid-like, fluid-like, and gas-like phases. Using breast cancer cell lines invading into engineered ECM, here we show that the spheroid interior develops spatial and temporal heterogeneities in material phase which, depending upon cell type and matrix density, ultimately result in a variety of phase separation patterns at the invasive front. Using a computational approach, we further show that these patterns are captured by a novel jamming phase diagram. We suggest that non-equilibrium phase separation based upon jamming and unjamming transitions may provide a unifying physical picture to describe cellular migratory dynamics within, and invasion from, a tumor., Graphical abstract, Highlights • Tumor spheroids invading into a 3D matrix exhibit coexistent material phases • Invasion leads to spatiotemporal heterogeneities consistent with jamming dynamics • Phase separation patterns are captured by a model-based jamming phase diagram • Effective thermodynamic variables Teff and Pconf capture cell and matrix properties, Biophysics; Cancer; Mechanobiology

Significance Tissues are composed of many cells that coordinate in space, through which tissue-level material characteristics emerge. While recent progress revealed that many biological processes are analogous to material phase transitions, a systematic framework to describe the spatial order of complex living systems has been missing, which limits our understanding of material phase transitions in living systems. We develop a unified method to quantify the evolution of spatial order across different types of disordered systems, including jammed thermal systems, two-dimensional cell monolayers, three-dimensional epithelial spheroids, and Drosophila embryos. Using scaling analysis, we show successful differentiation of gas-like, liquid-like, and solid-like phases in various living systems.

Control of the structure and function of three-dimensional multicellular tissues depends critically on the spatial and temporal coordination of cellular physical properties, yet the organizational principles that govern these events and their disruption in disease remain poorly understood. Using a multicellular mammary cancer organoid model, we map here the spatial and temporal evolution of positions, motions and physical characteristics of individual cells in three dimensions. Compared with cells in the organoid core, cells at the organoid periphery and the invasive front are found to be systematically softer, larger and more dynamic. These mechanical changes are shown to arise from supracellular fluid flow through gap junctions, the suppression of which delays the transition to an invasive phenotype. These findings highlight the role of spatiotemporal coordination of cellular physical properties in tissue organization and disease progression. A platform for probing the mechanics and migratory dynamics of a growing model breast cancer reveals that cells at the invasive edge are faster, softer and larger than those in the core. Eliminating the softer cells delays the transition to invasion.

The ability of a cell to regulate its mechanical properties is central to its function. Emerging evidence suggests that interactions between the cell nucleus and cytoskeleton influence cell mechanics through poorly understood mechanisms. Here we show that A- and B-type nuclear lamin isoforms distinctively modulate both nuclear and cellular volume and selectively stabilize the linker of nucleoskeleton and cytoskeleton (LINC) complexes that couple the nucleus to cytoskeletal actin and vimentin. We reveal, further, that loss of each of the four-known lamin isoforms in the mouse embryonic fibroblasts differentially affects cortical and cytoplasmic stiffness as well as cellular contractility, and then propose a LINC complex mediated model that explains these impaired mechanical phenotypes. Finally, we demonstrate that loss of each lamin isoform softens the nucleus in a manner that correlates with loss of heterochromatin. Together, these findings uncover distinctive roles for each lamin isoform in maintaining cellular and nuclear mechanics.

Significance Basement membranes (BMs) are thin layers of extracellular matrix ubiquitously found in animals surrounding various tissues. As a physical barrier, their mechanical properties are important in maintaining structural integrity of tissues, and their permeabilities are essential for molecule exchange and internal cell activities. However, due to the lack of direct measurement methods, the physical properties of BMs remain largely unclear, limiting our understanding of BMs in various physiological and pathological processes such as tumor development. Here, we apply pressure-controlled inflation/deflation to measure the stress–strain behaviors of intact BM in situ and to determine the mechanical properties in a model-independent manner. We discover a strong strain-stiffening effect of intact BM, which is essential for preventing its snap-through instability., Basement membrane (BM) is a thin layer of extracellular matrix that surrounds most animal tissues, serving as a physical barrier while allowing nutrient exchange. Although they have important roles in tissue structural integrity, physical properties of BMs remain largely uncharacterized, which limits our understanding of their mechanical functions. Here, we perform pressure-controlled inflation and deflation to directly measure the nonlinear mechanics of BMs in situ. We show that the BMs behave as a permeable, hyperelastic material whose mechanical properties and permeability can be measured in a model-independent manner. Furthermore, we find that BMs exhibit a remarkable nonlinear stiffening behavior, in contrast to the reconstituted Matrigel. This nonlinear stiffening behavior helps the BMs to avoid the snap-through instability (or structural softening) widely observed during the inflation of most elastomeric balloons and thus maintain sufficient confining stress to the enclosed tissues during their growth.

Current methods to obtain mesenchymal stem cells (MSCs) involve sampling, culturing, and expanding of primary MSCs from adipose, bone marrow, and umbilical cord tissues. However, the drawbacks are the limited numbers of total cells in MSC pools, and their decaying stemness during in vitro expansion. As an alternative resource, recent ceiling culture methods allow the generation of dedifferentiated fat cells (DFATs) from mature adipocytes. Nevertheless, this process of spontaneous dedifferentiation of mature adipocytes is laborious and time-consuming. This paper describes a modified protocol for in vitro dedifferentiation of adipocytes by employing an additional physical stimulation, which takes advantage of augmenting the stemness-related Wnt/β-catenin signaling. Specifically, this protocol utilizes a polyethylene glycol (PEG)-containing hypertonic medium to introduce extracellular physical stimulation to obtain higher efficiency and introduce a simpler procedure for adipocyte dedifferentiation.

Highlights An all-organic hybrid nanobullets labeled as ZPA@HA-ACVA-AZ NBs was developed for the “precise strike”of hypoxic tumors through an oxygen-independently synergistic PTT/TDT, possessing therapeutic advantages over traditional ROS-mediated cancer treatment.By feat of dual-targeting effect from surface-modified HA (targeting CD44 receptors) and AZ (targeting CA IX), the nanobullets accumulated at hypoxic tumors efficiently.The synergism of intelligent nanobullets could suppress the primary breast tumor growth and lung metastasis via CA IX inhibition by AZ and synergistic PTT/TDT. Supplementary Information The online version contains supplementary material available at 10.1007/s40820-021-00616-4., Hypoxia is a feature of solid tumors and it hinders the therapeutic efficacy of oxygen-dependent cancer treatment. Herein, we have developed all-organic oxygen-independent hybrid nanobullets ZPA@HA-ACVA-AZ for the “precise strike” of hypoxic tumors through the dual-targeting effects from surface-modified hyaluronic acid (HA) and hypoxia-dependent factor carbonic anhydrase IX (CA IX)-inhibitor acetazolamide (AZ). The core of nanobullets is the special zinc (II) phthalocyanine aggregates (ZPA) which could heat the tumor tissues upon 808-nm laser irradiation for photothermal therapy (PTT), along with the alkyl chain-functionalized thermally decomposable radical initiator ACVA-HDA on the side chain of HA for providing oxygen-independent alkyl radicals for ablating hypoxic cancer cells by thermodynamic therapy (TDT). The results provide important evidence that the combination of reverse hypoxia hallmarks CA IX as targets for inhibition by AZ and synergistic PTT/TDT possess incomparable therapeutic advantages over traditional (reactive oxygen species (ROS)-mediated) cancer treatment for suppressing the growth of both hypoxic tumors and their metastasis. Supplementary Information The online version contains supplementary material available at 10.1007/s40820-021-00616-4.

ASTRACT The early malignant tumor invades surrounding extracellular matrix (ECM) in a manner that depends upon material properties of constituent cells and ECM. Biophysical mechanisms remain unclear, however. Using a multicellular spheroid embedded within an engineered three-dimensional matrix, we show here the potential for coexistence of solid-like, fluid-like, and gas-like phases of the cellular collective described by a jamming phase diagram. Depending upon cell type (MCF-10A vs . MDA-MB-231) and ECM density (1 to 4 mg/ml collagen), cancer cells within the spheroid display a variety of collective behaviors, including a non-migratory jammed phase and a migratory unjammed phase. At a critical collagen density, unjammed cancer cells at the spheroid periphery transition in an almost switch-like fashion between distinct modes of invasion. In the case of MDA-MB-231, for example, we find that when ECM density is 2 mg/ml or smaller single cells and cell clusters scatter from the spheroid periphery in the form of discrete gas-like particles, but when ECM density is 3 mg/ml or greater these cells flow collectively from the spheroid periphery in continuous fluid-like invasive branches. These findings suggest coexistence within the spheroid mass of multiple material phases of the cellular collective –solid-like, fluid-like, and gas-like– in a manner that is superficially similar to common inanimate multiphasic systems at thermodynamic equilibrium, but here arising in living cellular systems, all of which are displaced far from thermodynamic equilibrium. We conclude that non-equilibrium phase separation based upon jamming dynamics may provide a new physical picture to describe cellular migratory dynamics within and invasion from a tumor mass. TWO-SENTENCE SUMMARY Using a multicellular spheroid embedded within an engineered three-dimensional matrix, we show here the potential for coexistence of solid-like, fluid-like, and gas-like phases of the cellular collective described by a jamming phase diagram. Depending upon cell type and matrix density, moreover, invasion into matrix from the tumor periphery can switch from a continuous cellular collective that flows like a fluid to discrete cells that scatter individually like a gas.

Cancer progression is driven by cell proliferation, apoptosis, and matrix invasion, which in turn depend on a myriad of factors including microenvironment stiffness, nutrient supply, and intercellular communication. Cell proliferation is regulated by volume, but in 3D clusters it remains unclear how multiple cells interact to control their size. In this study, we propose a mechano-osmotic model to investigate the evolution of volume dynamics within multicellular systems. Volume control depends on an interplay between multiple cellular constituents, including gap junctions, mechanosensitive ion channels, energy consuming ion transporters, and the actomyosin cortex, that coordinate to manipulate cellular osmolarity. In connected cells, mechanical loading is shown to significantly affect how these components cooperate to transport ions, and precise volume control is impacted by the emergence of osmotic pressure gradients between cells. Consequent increases in cellular ion concentrations drive swelling, while a loss of ions impedes the compression resistance of cells. Combining the modeling framework with novel experiments, we identify how gap junctions can amplify spatial variations in cell volume within multicellular spheroids and, further, describe how the process depends on proliferation-induced solid stress. Our model provides new insight into the role of gap junctions in cancer progression and can help guide the development of therapeutics that target inter- and extra-cellular ion transport.

Physical compression–induced dedifferentiation of adipocytes promotes tumor progression., Dysregulated physical stresses are generated during tumorigenesis that affect the surrounding compliant tissues including adipocytes. However, the effect of physical stressors on the behavior of adipocytes and their cross-talk with tumor cells remain elusive. Here, we demonstrate that compression of cells, resulting from various types of physical stresses, can induce dedifferentiation of adipocytes via mechanically activating Wnt/β-catenin signaling. The compression-induced dedifferentiated adipocytes (CiDAs) have a distinct transcriptome profile, long-term self-renewal, and serial clonogenicity, but do not form teratomas. We then show that CiDAs notably enhance human mammary adenocarcinoma proliferation both in vitro and in a xenograft model, owing to myofibrogenesis of CiDAs in the tumor-conditioned environment. Collectively, our results highlight unique physical interplay in the tumor ecosystem; tumor-induced physical stresses stimulate de novo generation of CiDAs, which feedback to tumor growth.

Active transport in the cytoplasm plays critical roles in living cell physiology. However, the mechanical resistance that intracellular compartments experience, which is governed by the cytoplasmic material property, remains elusive, especially its dependence on size and speed. Here we use optical tweezers to drag a bead in the cytoplasm and directly probe the mechanical resistance with varying size a and speed V We introduce a method, combining the direct measurement and a simple scaling analysis, to reveal different origins of the size- and speed-dependent resistance in living mammalian cytoplasm. We show that the cytoplasm exhibits size-independent viscoelasticity as long as the effective strain rate V/a is maintained in a relatively low range (0.1 s-1 < V/a < 2 s-1) and exhibits size-dependent poroelasticity at a high effective strain rate regime (5 s-1 < V/a < 80 s-1). Moreover, the cytoplasmic modulus is found to be positively correlated with only V/a in the viscoelastic regime but also increases with the bead size at a constant V/a in the poroelastic regime. Based on our measurements, we obtain a full-scale state diagram of the living mammalian cytoplasm, which shows that the cytoplasm changes from a viscous fluid to an elastic solid, as well as from compressible material to incompressible material, with increases in the values of two dimensionless parameters, respectively. This state diagram is useful to understand the underlying mechanical nature of the cytoplasm in a variety of cellular processes over a broad range of speed and size scales.

The ever-growing overlap between electronics and wearable technology is driving the demand for utilizing novel materials that are cost-effective, light-weight, eco-friendly, mechanically deformable and can be conformably and comfortably worn on human body as substrate to support the reliable operation of wearable electronic functionalities. Paper materials comprised of bio-origin ingredients (e.g., cellulose and carbon derivatives) have recently attracted remarkably increasing research and commercial interests for prototyping next-generation wearable electronics due to their superiorities including natural abundance, flyweight, mature manufacturing process, specific structural properties, favorable mechanical bendability, biocompatibility and nontoxicity over their counterparts. Feasibility of engaging paper materials has been proved by outstanding performances in body-worn healthcare sensing systems, electro-stimulated artificial muscles, on-site memory storage and wearable power supply on paper substrate. In this review, we present a state-of-the-art introduction of diverse paper substrate options and fabrication techniques employed for realizing paper electronics, and discuss both pros and cons of each manufacturing tactic. Additionally, we summarize developing trends of paper-based electronics in the emerging wearable applications. Based upon these, final conclusions, encountering challenges, accompanied with advancing outlooks are illustrated.

The behavior of living cells is significantly affected by the mechanical properties of the surrounding soft extracellular matrix (ECM) comprising of various types of biopolymers. More complexity is added as cell-generated forces in turn can mechanically modify their microenvironment. Moreover, these forces can also act as mechanical signals for other cells leading to emergent collective cell dynamics. Bulk measurement techniques are not capable of resolving these local mechanical interactions which are often hidden in 3D, thus, optical tweezers have emerged as a powerful tool to directly characterize microscale mechanics and forces at play. In this chapter, we first introduce a typical experimental setup of optical tweezers and calibration methods that has been widely accepted by the mechanobiology community. Subsequently, we discuss various ways in which optical tweezers can be used to probe mechanics at different length scales such as the cytoplasm at the sub-cellular level, at the level of whole cell and finally explore the cell-cell and cell-matrix interaction. Later, perspectives on the future development of optical tweezers to study cell-matrix interaction is also provided.

The aim of this study was to investigate the function of microRNA (miR)-193-3p in human intrahepatic cholangiocarcinoma (ICC) tissues and cells. To evaluate whether miR-193-3p was aberrantly upregulated, we used reverse transcription-quantitative polymerase chain reaction to detect the level of miR-193-3p in ICC tissues and ICC-9810 cells. The effects of miR-193-3p downregulation on ICC cell proliferation, migration and invasion were also measured by MTT, wound-healing and Transwell assays. Additionally, transforming growth factor-β receptor type 3 (TGFBR3) was investigated as a direct target of miR-193-3p by dual-luciferase reporter assays and western blot analyses. The results demonstrated that miR-193-3p was aberrantly upregulated in ICC tissues and cell lines. Furthermore, TGFBR3 was confirmed to be a target of miR-193-3p in ICC and was notably upregulated by miR-193-3p knockdown in the ICC-9810 cells. The knockdown of miR-193-3p also exerted direct inhibitory effects on the proliferation, migration and invasion of the ICC-9810 cells. Therefore, we present evidence that miR-193-3p plays a key role in promoting human ICC by regulating TGFBR3.

Double-emulsion droplets have found widespread applications in various engineering and biomedical fields because of their capability in encapsulating different components in each layer. The conventional double-emulsion method is the two-stage stirring emulsification method, which suffers from poor monodispersity and low encapsulation efficiency. With recent advances in microfabrication, some novel methods for fabricating double-emulsion droplets have been developed, including microfluidic emulsification (double-T-junction microchannel, double-cross-shaped microchannel and several three-dimensional microchannels), membrane emulsification and coaxial electrospraying. These methods have shown significantly improved droplet features (e.g., size, size uniformity, thickness of each layer, generation throughput capability). Herein, this paper first reviews the state-of-art approaches for fabricating double-emulsion droplets and discusses their advantages and disadvantages. The applications of double-emulsion droplets in biomedical fields, including cell encapsulation, drug delivery and controlled release, and synthetic biology are also discussed. In conclusion, future perspectives are given.

Experimentally measuring the apparent contact angle on a curved surface usually requires a specific instrument, which could be costly and is not widely accessible. To address this challenge, we proposed a simple wetting model to theoretically predict the apparent contact angle of a droplet on convex and concave spherical surfaces, which requires knowing the volume of the droplet, surface curvature and intrinsic contact angle. Using this theoretical model, we investigated the influence of radius and hydrophobicity of curved surfaces on wetting behaviors. For a concave surface, the droplet on it could exhibit a convex or concave morphology depending on the detailed parameters. The critical volume for a droplet changing from convex to concave shape was determined in this study. Employing this model, the contact angle on curved surface with microstructures was also investigated. The model may contribute to the understanding of natural wetting phenomenon and better design of related structures.

Cells alter their mechanical properties in response to their local microenvironment; this plays a role in determining cell function and can even influence stem cell fate. Here, we identify a robust and unified relationship between cell stiffness and cell volume. As a cell spreads on a substrate, its volume decreases, while its stiffness concomitantly increases. We find that both cortical and cytoplasmic cell stiffness scale with volume for numerous perturbations, including varying substrate stiffness, cell spread area, and external osmotic pressure. The reduction of cell volume is a result of water efflux, which leads to a corresponding increase in intracellular molecular crowding. Furthermore, we find that changes in cell volume, and hence stiffness, alter stem-cell differentiation, regardless of the method by which these are induced. These observations reveal a surprising, previously unidentified relationship between cell stiffness and cell volume that strongly influences cell biology.

International audience; Animal cells in tissues are supported by biopolymer matrices, which typically exhibit highly nonlinear mechanical properties. While the linear elasticity of the matrix can significantly impact cell mechanics and functionality, it remains largely unknown how cells, in turn, affect the nonlinear mechanics of their surrounding matrix. Here we show that living contractile cells are able to generate a massive stiffness gradient in three distinct 3D extracellular matrix model systems: collagen, fibrin, and Matrigel. We decipher this remarkable behavior by introducing Nonlinear Stress Inference Microscopy (NSIM), a novel technique to infer stress fields in a 3D matrix from nonlinear microrheology measurement with optical tweezers. Using NSIM and simulations, we reveal a long-ranged propagation of cell-generated stresses resulting from local filament buckling. This slow decay of stress gives rise to the large spatial extent of the observed cell-induced matrix stiffness gradient, which could form a mechanism for mechanical communication between cells.

This paper studies air defense system kill zone, air ship missile firing mode and air ship missile launch area that impact air ship missile load matrix determine key problems, establishes air ship missile carrier array’s mathematics model, makes simulation calculation of the model, and analyzes simulation results, and gets the influence law of vehicle speed, height, target motion characteristics, deviation angle and pitching angle on attack matrix, and the results can provide reference for determining air ship missile carrier aircraft attack array.

Regenerative medicine has rapidly evolved over the past decade owing to its potential applications to improve human health. Targeted differentiations of stem cells promise to regenerate a variety of tissues and/or organs despite significant challenges. Recent studies have demonstrated the vital role of the physical microenvironment in regulating stem cell fate and improving differentiation efficiency. In this review, we summarize the main physical cues that are crucial for controlling stem cell differentiation. Recent advances in the technologies for the construction of physical microenvironment and their implications in controlling stem cell fate are also highlighted.

Resistance to the Bruton’s tyrosine kinase (BTK) inhibitor ibrutinib has been attributed solely to mutations in BTK and related pathway molecules. Using whole-exome and deep-targeted sequencing, we dissect evolution of ibrutinib resistance in serial samples from five chronic lymphocytic leukaemia patients. In two patients, we detect BTK-C481S mutation or multiple PLCG2 mutations. The other three patients exhibit an expansion of clones harbouring del(8p) with additional driver mutations (EP300, MLL2 and EIF2A), with one patient developing trans-differentiation into CD19-negative histiocytic sarcoma. Using droplet-microfluidic technology and growth kinetic analyses, we demonstrate the presence of ibrutinib-resistant subclones and estimate subclone size before treatment initiation. Haploinsufficiency of TRAIL-R, a consequence of del(8p), results in TRAIL insensitivity, which may contribute to ibrutinib resistance. These findings demonstrate that the ibrutinib therapy favours selection and expansion of rare subclones already present before ibrutinib treatment, and provide insight into the heterogeneity of genetic changes associated with ibrutinib resistance., University of Texas M.D. Anderson Cancer Center (Support Grant CA016672), National Science Foundation (U.S.) (DMR-1310266), Harvard University. Materials Research Science and Engineering Center (DMR-1420570), National Natural Science Foundation (China) (81372496)

To investigate the practicability of establishing zebrafish lipid-lowering drug screening model and the effect of berberine (BBR) on hyperlipidemic zebrafish. Three-month-old zebrafishes were fed with 4% cholesterol for 0, 2, 4, 8, 14, 20, 25, 30 days, and the level of total cholesterol in serum was measured. Zebrafish were randomly divided into four groups: the control group, the high cholesterol diet group, the 0.01% simvastatin-treated group, the 0.1% berberine-treated group and the 0.2% berberine-treated group. The levels of total cholesterol (TC), triglyceride (TC), low density lipoprotein cholesterol (LDL-c) and high-density lipoprotein cholesterol (HDL-c) in serum were measured; the expression of hepatic HMGCR, LDLR and CYP7A1a mRNA expressions were detected by real time PCR. Oil red O staining was performed to observe the changes in fat content in the liver. According to the result, the level of serum TC in the 4% cholesterol diet group significantly was higher than that of the normal control group in a time-dependent manner and reached a stable level at the 20th day. The BBR group showed significant decreases in the levels of TC, TG and LDL-c, HMGCR mRNA expression and fat content and increases in LDLR and CYP7A1a mRNA. The hyperlipidemia zebrafish model was successfully established by feeding with 4% cholesterol for 20 days. The findings lay a foundation for further screenings on lipid-lowering drugs.

Cells tend to form hierarchy structures in native tissues. Formation of cell aggregates in vitro such as cancer spheroids and embryonic bodies provides a unique means to study the mechanical properties and biological behaviors/functions of their counterparts in vivo. In this paper, we review state-of-the-art experimental approaches to assess the mechanical properties and mechanically-induced responses of cell aggregates in vitro. These approaches are classified into five categories according to loading modality, including micropipette aspiration, centrifugation, compression loading, substrate distention, and fluid shear loading. We discussed the advantages and disadvantages of each approach, and the potential biomedical applications. Understanding of the mechanical behavior of cell aggregates provides insights to physical interactions between cells and integrity of biological functions, which may enable mechanical intervention for diseases such as atheromatosis and cancer.

The integration of paper with an electrochemical device has attracted growing attention for point-of-care testing, where it is of great importance to fabricate electrodes on paper in a low-cost, easy and versatile way. In this work, we report a simple strategy for directly writing electrodes on paper using a pressure-assisted ball pen to form a paper-based electrochemical device (PED). This method is demonstrated to be capable of fabricating electrodes on paper with good electrical conductivity and electrochemical performance, holding great potential to be employed in point-of-care applications, such as in human health diagnostics and food safety detection. As examples, the PEDs fabricated using the developed method are applied for detection of glucose in artificial urine and melamine in sample solutions. Furthermore, our developed strategy is also extended to fabricate PEDs with multi-electrode arrays and write electrodes on non-planar surfaces (e.g., paper cup, human skin), indicating the potential application of our method in other fields, such as fabricating biosensors, paper electronics etc.

Human noroviruses (HuNoVs) are positive-sense RNA viruses that can cause severe, highly infectious gastroenteritis. HuNoV outbreaks are frequently associated with recombination between circulating strains. Strain genotyping and phylogenetic analyses show that noroviruses often recombine in a highly conserved region near the junction of the viral polyprotein (open reading frame 1 [ORF1]) and capsid (ORF2) genes and occasionally within the RNA-dependent RNA polymerase (RdRP) gene. Although genotyping methods are useful for tracking changes in circulating viral populations, they report only the dominant recombinant strains and do not elucidate the frequency or range of recombination events. Furthermore, the relatively low frequency of recombination in RNA viruses has limited studies to cell culture or in vitro systems, which do not reflect the complexities and selective pressures present in an infected organism. Using two murine norovirus (MNV) strains to model coinfection, we developed a microfluidic platform to amplify, detect, and recover individual recombinants following in vitro and in vivo coinfection. One-step reverse transcriptase PCR (RT-PCR) was performed in picoliter drops with primers that identified the wild-type and recombinant progenies and scanned for recombination breakpoints at ∼1-kb intervals. We detected recombination between MNV strains at multiple loci spanning the viral protease, RdRP, and capsid ORFs and isolated individual recombinant RNA genomes that were present at a frequency of 1/300,000 or higher. This study is the first to examine norovirus recombination following coinfection of an animal and suggests that the exchange of RNA among viral genomes in an infected host occurs in multiple locations and is an important driver of genetic diversity. IMPORTANCE RNA viruses increase diversity and escape host immune barriers by genomic recombination. Studies using a number of viral systems indicate that recombination occurs via template switching by the virus-encoded RNA-dependent RNA polymerase (RdRP). However, factors that govern the frequency and positions of recombination in an infected organism remain largely unknown. This work leverages advances in the applied physics of drop-based microfluidics to isolate and sequence rare recombinants arising from the coinfection of mice with two distinct strains of murine norovirus. This study is the first to detect and analyze norovirus recombination in an animal model.

Deoxyribonucleic acid (DNA) emerges as building bricks for the fabrication of nanostructure with complete artificial architecture and geometry. The amazing ability of DNA in building two- and three-dimensional structures raises the possibility of developing smart nanomachines with versatile controllability for various applications. Here, we overviewed the recent progresses in engineering DNA machines for specific bioengineering and biomedical applications.

Novel wetting strategies in plants have inspired numerous notable biomimetic surfaces over the past decade, such as self-cleaning surfaces mimicking the water repellency of lotus leaves and directional water transport surfaces imitating the slippery surface on carnivorous plants. Here, a new wetting behavior in dandelion seed (genus Taraxacum) is found, characterized by capturing a droplet inside it. The critical conditions required for wetting of the fiber assay in terms of the fibrous geometry and liquid surface tension are identified, and how these factors quantitatively affect the volume of the captured droplet is shown further. More importantly, the reverse process can be triggered by introducing a competitive liquid phase with smaller surface tension to the wetted fiber assay, as it is demonstrated by the release of the captured water droplet in oil. These results enhance the understanding on wetting of fibrous structures and would benefit the design of novel intelligent and responsive devices. This newly identified wetting behavior holds great potential for fine control and micromanipulation of liquid. As a demonstration, it is illustrated that the natural fibrous structure is capable of manipulating a small volume of liquid for droplet-based multiplexed chemical reaction.

With significant potential as a robust source to produce specific somatic cells for regenerative medicine, stem cells have attracted increasing attention from both academia and government. In vivo, stem cell differentiation is a process under complicated regulations to precisely build tissue with unique spatial structures. Since multicellular spheroidal aggregates of stem cells, commonly called as embryoid bodies (EBs), are considered to be capable of recapitulating the events in early stage of embryonic development, a variety of methods have been developed to form EBs in vitro for studying differentiation of embryonic stem cells. The regulation of stem cell differentiation is crucial in directing stem cells to build tissue with the correct spatial architecture for specific functions. However, stem cells within the three-dimensional multicellular aggregates undergo differentiation in a less unpredictable and spatially controlled manner in vitro than in vivo. Recently, various microengineering technologies have been developed to manipulate stem cells in vitro in a spatially controlled manner. Herein, we take the spotlight on these technologies and researches that bring us the new potential for manipulation of stem cells for specific purposes.

We characterized regulation of the human monocyte chemoattractant protein-1 (hMCP-1) gene by IFN-γ in astrocytoma cells, because astroglial cells express chemokines in several central nervous system inflammatory states. It was found that IFN-γ-induced hMCP-1 transcription was rapid, transient, and mediated by a 213-bp promoter-proximal regulatory region of the gene. Our studies on both in vitro and in vivo states of the hMCP-1 regulatory region established requirement of an IFN-γ-activated site (GAS) and the presence of IFN-γ-inducible GAS-binding activity involving at least STAT-1α for IFN-γ-induced hMCP-1 expression. Unexpectedly, in vivo genomic footprinting of the proximal regulatory region of the IFN-γ-induced gene revealed protection of a GC-rich sequence (GC box) with the same temporal pattern as that seen at the GAS; in vitro, this GC-rich element is associated with nuclear factor Sp1. These observations suggested a cooperative interaction between the GAS and the GC box element. Interestingly, site-specific mutations that abolished GC-box or GAS-element function produced clearly disparate results. Disruption of the GC box did not affect fold induction by IFN-γ but reduced promoter-reporter expression by half. Conversely, GAS mutation abrogated induction but did not affect the magnitude of expression. These results establish the importance of the GAS element for induction of hMCP-1 and further our understanding of IFN-γ-mediated transcriptional induction by providing the first evidence in vivo for inducible signaling to the GC box by this cytokine.

Osteosarcoma and chondrosarcoma are malignant bone tumors, and they significantly affect the life quality of patients including children and adults. The main treatment method is surgical amputation of the malignant lesion, despite that recurrence often occurs. Recently, it has been observed that TiO2 NPs killed HeLa cells effectively via photocatalysis in vitro, which indicates titanium dioxide (TiO2) nanoparticles (NPs) might be used to reduce the recurrence of osteosarcoma and chondrosarcoma by inducing cytotoxicity to bone tumor cells. In this study, we investigated the potential effects of TiO2 NPs in two cancer cell lines in vitro: U-2 OS (osteosarcoma) and SW 1353 (chondrosarcoma). We assessed cell viability, the levels of reactive oxygen species (ROS) and glutathione (GSH) after exposure to TiO2 NPs at different concentrations (0.1-100 microg/ml) for varying exposure periods (12-48 hours). Compared to the NP-free control, TiO2 NPs induced cell death in a dosage-dependent and time-dependent manner. The median inhibitory concentration (IC50) of TiO2 NPs at 24 hours was 211.3 +/- 15.2 microg/ml and 5408.8 +/- 45.9 microg/ml for SW 1353 and U-2 OS cell lines, respectively. TiO2 NPs concentrations above 1 microg/ml were more efficient to reduce the cell viability of SW 1353 than U-2 OS of NPs at all exposure times. The increased ROS and reduced GSH levels indicated that TiO2 NPs killed cancer cells through oxidative stress. These results suggested that the TiO2 NPs can be potentially used to minimize/prevent the recurrence of osteosarcoma and chondrosarcoma.

A novel strategy by means of poly diallyl dimethylammonium chloride (PDDA) was used to make highly mono-dispersed positively charged gold nanoparticles, and 5-ALA was immobilized onto the gold nanoparticles through electrostatic interaction. The conjugation of 5-aminolevulinic acid (5-ALA) and gold nanopartilces were characterized by the integrated tools of resonance Rayleigh scattering (RRS), UV-Vis absorption spectra, transmission electron microscopy (TEM) and laser light scattering. The results demonstrated that 5-ALA can be attached onto positively charged gold nanoparticles. This new photosensitizer is significant for enhancing PDT efficacy clinically.

Cell mechanical microenvironment (CMM) significantly affects cell behaviors such as spreading, migration, proliferation and differentiation. However, most studies on cell response to mechanical stimulation are based on two-dimensional (2D) planar substrates, which cannot mimic native three-dimensional (3D) CMM. Accumulating evidence has shown that there is a significant difference in cell behavior in 2D and 3D microenvironments. Among the materials used for engineering 3D CMM, hydrogels have gained increasing attention due to their tunable properties (e.g. chemical and mechanical properties). In this paper, we provide an overview of recent advances in engineering hydrogel-based 3D CMM. Effects of mechanical cues (e.g. hydrogel stiffness and externally induced stress/strain in hydrogels) on cell behaviors are described. A variety of approaches to load mechanical stimuli in 3D hydrogel-based constructs are also discussed.

The unique benefit of electrostatic self-assembly of microscale components in solution is demonstrated for the first time. In particular, positive and negative treatment of poly(ethylene glycol) (PEG) facilitates a novel bottom-up assembly approach using electrostatic interaction from microgels with opposite charges. Fundamental investigations of electrostatic interaction of microgels reveal that the contact area of microgels determines the total energy of construct and thus the final patterns. The electrostatic self-assembly approach enables the fabrication of large and complex biological related structures (e.g., multi-layer spheroid) with accurate control. By the design of the microgels, the thickness and number of microgels in each layer can be controlled. Biological investigations of positive and negative treatments of PEG further prove the possibility of using this approach in tissue engineering, regenerative medicine and drug delivery.

Lateral flow assays (LFAs) as rapid analytical techniques promise to be widely used in point-of-care (POC) diagnostics because of their affordability and simplicity. However, LFAs still suffer from low sensitivity in detection of various biomarkers, e.g., nucleic acids. In this study, we developed a simple and general one-step signal amplification strategy, which employed oligonucleotide-linked gold nanoparticle (AuNP) aggregates to enhance the sensitivity in nucleic acid lateral flow (NALF) assays. Using a nucleic acid sequence of human immunodeficiency virus type 1 (HIV-1) as a model analyte, we observed that the detection limit of the developed NALF assay was 0.1 nM, which was improved by 2.5-fold compared with that of a non-signal amplification approach. The methodology described here could be used to detect a broad range of nucleic acids, and the general signal amplification approach could be potentially adopted in other types of LFAs.

Heart disease is one of the major global health issues. Despite rapid advances in cardiac tissue engineering, limited successful strategies have been achieved to cure cardiovascular diseases. This situation is mainly due to poor understanding of the mechanism of diverse heart diseases and unavailability of effective in vitro heart tissue models for cardiovascular drug screening. With the development of microengineering technologies, three-dimensional (3D) cardiac microtissue (CMT) models, mimicking 3D architectural microenvironment of native heart tissues, have been developed. The engineered 3D CMT models hold greater potential to be used for assessing effective drugs candidates than traditional two-dimensional cardiomyocyte culture models. This review discusses the development of 3D CMT models and highlights their potential applications for high-throughput screening of cardiovascular drug candidates.