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    Home > Biochemistry News > Biotechnology News > Tools such as PDMS's elastic materials help reveal cellular processes such as embryonic development.

    Tools such as PDMS's elastic materials help reveal cellular processes such as embryonic development.

    • Last Update: 2020-09-02
    • Source: Internet
    • Author: User
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    Under a microscope, cells are usually stationary, but in fact they are dynamic structures.
    cells squeeze, stretch, bend, and travel through their surroundings, they generate force.
    these forces are so small that they may weigh only one billionth of the weight of a curved pin.
    but they have profound biological implications.
    in fast-growing embryos, the force of this change can alter the cell development process," telling "when they stop differentiation and begin to transform."
    the concept of this physical force affecting cell function was put forward as early as 1 century ago.
    At the time, Scottish scientist Dr Arcy Thompson noted that "cells and tissues, shells and bones, leaves and flowers are many parts of matter that follow the laws of physics and are based on the principles of movement, forging and equality."
    " Thompson's theoretical framework paved the way for a great deal of biomemics research.
    " biomemass is a very old field that has been neglected for a long time.
    ," said Carsten Grashoff, an expert in cytometics at the Institute of Biochemistry at the German Mapu Society.
    partly because researchers lack the tools to measure molecular power.
    now, scientists have been able to use microscopes to map skin cells "moving forward" as wounds heal.
    , of course, obstacles remain, scientists are still trying to distinguish between cellular forces and random biological noise, and they have difficulty studying processes in the complex internal environment of living organisms.
    but by combining "biometrics" tools with other genetic and biochemical methods, scientists are beginning to understand how these forces are translated into function.
    " life process is not only a biochemical signaling path.
    When you pull a protein, you may want to turn a binding point on or off, and pull the switch to choose which process is a cell," said Beth Pruitt, a mechanical engineer at Stanford University in the United States.
    " to obtain the interaction of traction cells with their surroundings, largely by relying on proteins embedded in their cell membranes.
    some proteins respond when they are "squeezed" by flowing liquids, such as the processes that occur in blood vessels, and some release pull-related signals when cells are squeezed by neighbors or other proteins.
    1990s, scientists developed a tool called a traction microscope (TFM).
    TFM became the first tool to quantify these forces.
    , for example, in 1999, Yu-Li Wang, then a faculty professor at the University of Massachusetts School of Medicine, and Mikah Dembo of Boston University placed fibroblasts in gel materials and embedded fluorescent balls.
    , the researchers used TFM to infer the force of cell production by measuring the displacement of the ball.
    " it's like a spring scale.
    ," says Ben Fabry, a biophysicist at friedrich Alexander Erlangen Nuremberg University in Germany, "when you apply weight to a spring and measure its deformation, if you know how strong the spring is, you can tell how strong it is."
    ", TFM has become the standard method for studying individual cells and interconnected cells.
    Clare Waterman of the National Institute of Heart, Lungs and Blood in Maryland used TFM to study cell movement, a process that is partly driven by the structure of cells called sticky spots.
    force is applied when they are docked to the surrounding extracellular substation (ECM).
    Waterman team has developed new ways to increase the number of small balls to image TFM experiments and produce ultra-high-resolution images.
    "We set 50 markers under each sticky spot.
    ," she said.
    team to reveal how the forces produced by sticky plaques trigger molecular events to integrate molecular motion.
    , of course, the multi-dimensional movement produced by cell movement is more complex than a one-dimensional spring scale.
    even though modern computing methods have made TFM technology easier to use, it initially required powerful supercomputers to interpret data.
    , the technology has many potential sources of error.
    "If a cell stretches in the opposite direction, it looks largely deformed."
    ," Waterman said, "it's also difficult to deal with when the ball's motion goes beyond the cell boundary."
    team is also extending TFM technology to 3D to better reflect biological realities.
    example, Fabry and colleagues used collagen from gels to build 3D models that track cellular forces.
    team was able to detect the shape of breast cancer cells, the forces they produce, and the speed and direction of movement.
    addition, to break the computational burden, Princeton University biomedical engineer Eleste Nelson was reluctant to accept low-resolution data from his organ development studies.
    we are more concerned with finding the relative difference in magnitude of forces that run through tens of thousands of cells as a whole," he said.
    ," she said.
    new tools as an easier option, some researchers have opted to use smaller polymer probes.
    the device can directly read out cellular forces.
    tool, developed by Boston University bioengineer Christopher Chen and colleagues, contains an elastic material called PDMS with a row of flexible columns, like the bristles of a toothbrush.
    these nano-pillars are covered with ECM proteins so that the cells attach.
    " they're a bit like mini springs.
    , a former postdoctoral student at Chen, said, "By measuring bending, people can identify and measure the external forces applied to each column."
    " micro-pillar array data can more easily interpret the data of TFM experiments and require less computational analysis.
    device itself is easy to manufacture and compatible with fluorescence microscopes.
    but these arrays also impose a special pattern of cell and their substation interaction.
    , this pattern is also affected by the arrangement and size of the columns.
    researchers can also make a culture base surface by changing the arrangement of the micro-pillars.
    shorter, thicker columns are stiffer and less prone to bending.
    of these columns can trigger considerable changes in cell stents , a network of proteins that form the physical basis of cells and help them conduct and respond to external forces.
    in turn, it can also affect cell proliferation, movement, and maturation.
    other researchers used molecular sensors to measure cellular forces.
    these devices can produce small-scale changes in the fluorescent signal's response to pull.
    such sensors are primarily based on fluorescent resonance energy transfer (FRET), a phenomenon that excites each other when the physical position of one fluorescent molecule or fluorop fluorescent group approaches another.
    Grashoff and colleagues have developed a FRET-based pull sensor.
    team measured extracellular forces using sensors that do not require hard-stuffed proteins.
    emory University biophysicist Khalid Salaita's team developed several of these probes, one fixed to solid surfaces such as glass carriers and the other to a biomolec molecule that binds to the target cell surface protein.
    the ability of active power scientists to measure forces within cells is itself a source of euphoria.
    these insights will yield valuable clinical benefits.
    Salaita believes that experiments measuring the power of individual cells will help scientists identify the safety of drugs that can directly interfere with tumor development.
    " movement and invasion of tumor cells is fatal, and if you can shut down the process and the drug has no cytotoxins, it may be a more precise tool.
    ," he said.
    but there are many biological problems that need to be explored at the tissue or organ level.
    " you can't predict tissue using isolated cells.
    ," Nelson said, "the connection between cells seems to be important for the production and transmission of in-tissue forces."
    " In many experiments, Nelson used artificial epiderm tissue to study the forces associated with organ formation.
    team used stem cells to differentiate into specific tissues, such as Pruitt's use of stem cell-derived cardiomyocytes to study the biometical effects of heart disease.
    hopes scientists will eventually explore the effects of Thompson's 100-year-old hypothesis.
    , I think, the field is revealing the mechanical forces that play a big role when the organization eventually forms," he said.
    ," she said.
    but scientists still need more tools.
    long-term use of most force measurement experiments, which limits their application value, for example, drug screening requires parallel analysis of large numbers of cells.
    Fabry's team is developing ways to automate and accelerate TFM experiments.
    "We wanted to measure the response of tens of thousands of cells simultaneously in a 3D model.
    ," he said.
    , measuring cellular forces in living organisms is also a challenge.
    a solution for fret sensors, and Otger Camp?s, a mechanical engineer at the University of California, Santa Barbara, and colleagues recently designed another device.
    team injected oil droplets with fluorescent particles into the living body, which were protein-modified to bind to the cell surface.
    measured the deformation of oil droplets, the researchers were able to determine the force between cells.
    , perhaps most fundamentally, an experimental technique is needed to help scientists manipulate force-response molecules more precisely.
    " will help us answer many questions directly.
    ," Nelson said.
    .
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