Biomechanics of Neutrophil Tethers

Leukocytes, including neutrophils, which are propelled by blood flow, can roll on inflamed endothelium using transient bonds between selectins and their ligands, and integrins and their ligands. When such receptor–ligand bonds last long enough, the leukocyte microvilli become extended and eventually form thin, 20 m long tethers. Tether formation can be observed in blood vessels in vivo and in microfluidic flow chambers. Tethers can also be extracted using micropipette aspiration, biomembrane force probe, optical trap, or atomic force microscopy approaches. Here, we review the biomechanical properties of leukocyte tethers as gleaned from such measurements and discuss the advantages and disadvantages of each approach. We also review and discuss viscoelastic models that describe the dependence of tether formation on time, force, rate of loading, and cell activation. We close by emphasizing the need to combine experimental observations with quantitative models and computer simulations to understand how tether formation is affected by membrane tension, membrane reservoir, and interactions of the membrane with the cytoskeleton.

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Cryogenic atomic force microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100084570 ◽

1991 ◽

Vol 49 ◽

pp. 54-55

Author(s):

K. A. Fisher ◽

M. G. L. Gustafsson ◽

M. B. Shattuck ◽

J. Clarke

Keyword(s):

Room Temperature ◽

Rapid Freezing ◽

Cryogenic Temperatures ◽

Soft Or ◽

Electrically Conductive ◽

Force Microscopy ◽

Flexible Molecules ◽

Advantages And Disadvantages ◽

Atomic Force ◽

Chemical Perturbation

The atomic force microscope (AFM) is capable of imaging electrically conductive and non-conductive surfaces at atomic resolution. When used to image biological samples, however, lateral resolution is often limited to nanometer levels, due primarily to AFM tip/sample interactions. Several approaches to immobilize and stabilize soft or flexible molecules for AFM have been examined, notably, tethering coating, and freezing. Although each approach has its advantages and disadvantages, rapid freezing techniques have the special advantage of avoiding chemical perturbation, and minimizing physical disruption of the sample. Scanning with an AFM at cryogenic temperatures has the potential to image frozen biomolecules at high resolution. We have constructed a force microscope capable of operating immersed in liquid n-pentane and have tested its performance at room temperature with carbon and metal-coated samples, and at 143° K with uncoated ferritin and purple membrane (PM).

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Rapid, Refined, and Robust Method for Expression, Purification, and Characterization of Recombinant Human Amyloid-beta M1-42

10.26434/chemrxiv.7725002.v1 ◽

2019 ◽

Author(s):

Priya Prakash ◽

Travis Lantz ◽

Krupal P. Jethava ◽

Gaurav Chopra

Keyword(s):

Amyloid Beta ◽

Western Blots ◽

Force Microscopy ◽

E Coli ◽

Atomic Force ◽

Set Up ◽

Short Time

Amyloid plaques found in the brains of Alzheimer’s disease (AD) patients primarily consists of amyloid beta 1-42 (Ab42). Commercially, Ab42 is synthetized using peptide synthesizers. We describe a robust methodology for expression of recombinant human Ab(M1-42) in Rosetta(DE3)pLysS and BL21(DE3)pLysS competent E. coli with refined and rapid analytical purification techniques. The peptide is isolated and purified from the transformed cells using an optimized set-up for reverse-phase HPLC protocol, using commonly available C18 columns, yielding high amounts of peptide (~15-20 mg per 1 L culture) in a short time. The recombinant Ab(M1-42) forms characteristic aggregates similar to synthetic Ab42 aggregates as verified by western blots and atomic force microscopy to warrant future biological use. Our rapid, refined, and robust technique to purify human Ab(M1-42) can be used to synthesize chemical probes for several downstream in vitro and in vivo assays to facilitate AD research.

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Controlling T cells spreading, mechanics and activation by micropatterning

Scientific Reports ◽

10.1038/s41598-021-86133-1 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Anaïs Sadoun ◽

Martine Biarnes-Pelicot ◽

Laura Ghesquiere-Dierickx ◽

Ambroise Wu ◽

Olivier Théodoly ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

T Cell Activation ◽

Cell Activation ◽

Young Modulus ◽

Careful Examination ◽

Adhesion Receptor ◽

Force Microscopy ◽

Atomic Force ◽

Micro Patterns

AbstractWe designed a strategy, based on a careful examination of the activation capabilities of proteins and antibodies used as substrates for adhering T cells, coupled to protein microstamping to control at the same time the position, shape, spreading, mechanics and activation state of T cells. Once adhered on patterns, we examined the capacities of T cells to be activated with soluble anti CD3, in comparison to T cells adhered to a continuously decorated substrate with the same density of ligands. We show that, in our hand, adhering onto an anti CD45 antibody decorated surface was not affecting T cell calcium fluxes, even adhered on variable size micro-patterns. Aside, we analyzed the T cell mechanics, when spread on pattern or not, using Atomic Force Microscopy indentation. By expressing MEGF10 as a non immune adhesion receptor in T cells we measured the very same spreading area on PLL substrates and Young modulus than non modified cells, immobilized on anti CD45 antibodies, while retaining similar activation capabilities using soluble anti CD3 antibodies or through model APC contacts. We propose that our system is a way to test activation or anergy of T cells with defined adhesion and mechanical characteristics, and may allow to dissect fine details of these mechanisms since it allows to observe homogenized populations in standardized T cell activation assays.

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Membrane fusion studied by colloidal probes

European Biophysics Journal ◽

10.1007/s00249-020-01490-5 ◽

2021 ◽

Vol 50 (2) ◽

pp. 223-237 ◽

Cited By ~ 1

Author(s):

Hannes Witt ◽

Filip Savić ◽

Sarah Verbeek ◽

Jörn Dietz ◽

Gesa Tarantola ◽

...

Keyword(s):

Membrane Fusion ◽

Optical Tweezers ◽

Three Dimensional ◽

Biological Processes ◽

Supported Membranes ◽

Supported Bilayers ◽

Force Microscopy ◽

Advantages And Disadvantages ◽

Atomic Force ◽

Colloidal Probes

AbstractMembrane-coated colloidal probes combine the benefits of solid-supported membranes with a more complex three-dimensional geometry. This combination makes them a powerful model system that enables the visualization of dynamic biological processes with high throughput and minimal reliance on fluorescent labels. Here, we want to review recent applications of colloidal probes for the study of membrane fusion. After discussing the advantages and disadvantages of some classical vesicle-based fusion assays, we introduce an assay using optical detection of fusion between membrane-coated glass microspheres in a quasi two-dimensional assembly. Then, we discuss free energy considerations of membrane fusion between supported bilayers, and show how colloidal probes can be combined with atomic force microscopy or optical tweezers to access the fusion process with even greater detail.

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Silane-Coating Strategy for Titanium Functionalization Does Not Impair Osteogenesis In Vivo

Materials ◽

10.3390/ma14071814 ◽

2021 ◽

Vol 14 (7) ◽

pp. 1814

Author(s):

Plinio Mendes Senna ◽

Carlos Fernando de Almeida Barros Mourão ◽

Rafael Coutinho Mello-Machado ◽

Kayvon Javid ◽

Pietro Montemezzi ◽

...

Keyword(s):

Bone Formation ◽

Photoelectron Spectroscopy ◽

Titanium Surface ◽

Rabbit Model ◽

Biologically Active ◽

Force Microscopy ◽

Atomic Force ◽

Silane Coating ◽

Titanium Screws

Silane-coating strategy has been used to bind biological compounds to the titanium surface, thereby making implant devices biologically active. However, it has not been determined if the presence of the silane coating itself is biocompatible to osseointegration. The aim of the present study was to evaluate if silane-coating affects bone formation on titanium using a rabbit model. For this, titanium screw implants (3.75 by 6 mm) were hydroxylated in a solution of H2SO4/30% H2O2 for 4 h before silane-coating with 3-aminopropyltriethoxysilane (APTES). A parallel set of titanium screws underwent only the hydroxylation process to present similar acid-etched topography as a control. The presence of the silane on the surface was checked by x-ray photoelectron spectroscopy (XPS), with scanning electron microscopy (SEM) and atomic force microscopy (AFM). A total of 40 titanium screws were implanted in the tibia of ten New Zealand rabbits in order to evaluate bone-to-implant contact (BIC) after 3 weeks and 6 weeks of healing. Silane-coated surface presented higher nitrogen content in the XPS analysis, while micro- and nano-topography of the surface remained unaffected. No difference between the groups was observed after 3 and 6 weeks of healing (p > 0.05, independent t-test), although an increase in BIC occurred over time. These results indicate that silanization of a titanium surface with APTES did not impair the bone formation, indicating that this can be a reliable tool to anchor osteogenic molecules on the surface of implant devices.

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Diabetes increases stiffness of live cardiomyocytes measured by atomic force microscopy nanoindentation

AJP Cell Physiology ◽

10.1152/ajpcell.00192.2013 ◽

2014 ◽

Vol 307 (10) ◽

pp. C910-C919 ◽

Cited By ~ 22

Author(s):

Juan C. Benech ◽

Nicolás Benech ◽

Ana I. Zambrana ◽

Inés Rauschert ◽

Verónica Bervejillo ◽

...

Keyword(s):

Atomic Force Microscopy ◽

Physiological Condition ◽

Diabetic Mice ◽

Cell Nuclei ◽

Buffer Solution ◽

Isolated Cardiomyocytes ◽

Force Microscopy ◽

Atomic Force ◽

Myocardial Fibers

Stiffness of live cardiomyocytes isolated from control and diabetic mice was measured using the atomic force microscopy nanoindentation method. Type 1 diabetes was induced in mice by streptozotocin administration. Histological images of myocardium from mice that were diabetic for 3 mo showed disorderly lineup of myocardial cells, irregularly sized cell nuclei, and fragmented and disordered myocardial fibers with interstitial collagen accumulation. Phalloidin-stained cardiomyocytes isolated from diabetic mice showed altered (i.e., more irregular and diffuse) actin filament organization compared with cardiomyocytes from control mice. Sarco/endoplasmic reticulum Ca2+-ATPase (SERCA2a) pump expression was reduced in homogenates obtained from the left ventricle of diabetic animals compared with age-matched controls. The apparent elastic modulus (AEM) for live control or diabetic isolated cardiomyocytes was measured using the atomic force microscopy nanoindentation method in Tyrode buffer solution containing 1.8 mM Ca2+ and 5.4 mM KCl (physiological condition), 100 nM Ca2+ and 5.4 mM KCl (low extracellular Ca2+ condition), or 1.8 mM Ca2+ and 140 mM KCl (contraction condition). In the physiological condition, the mean AEM was 112% higher for live diabetic than control isolated cardiomyocytes (91 ± 14 vs. 43 ± 7 kPa). The AEM was also significantly higher in diabetic than control cardiomyocytes in the low extracellular Ca2+ and contraction conditions. These findings suggest that the material properties of live cardiomyocytes were affected by diabetes, resulting in stiffer cells, which very likely contribute to high diastolic LV stiffness, which has been observed in vivo in some diabetes mellitus patients.

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Advanced Hydrogels for Cartilage Tissue Engineering: Recent Progress and Future Directions

Polymers ◽

10.3390/polym13234199 ◽

2021 ◽

Vol 13 (23) ◽

pp. 4199

Author(s):

Mahshid Hafezi ◽

Saied Nouri Khorasani ◽

Mohadeseh Zare ◽

Rasoul Esmaeely Neisiany ◽

Pooya Davoodi

Keyword(s):

Tissue Engineering ◽

Cartilage Tissue Engineering ◽

Cartilage Regeneration ◽

Biomechanical Properties ◽

Tissue Growth ◽

Cartilage Tissue ◽

Self Healing ◽

Advantages And Disadvantages ◽

Wide Range

Cartilage is a tension- and load-bearing tissue and has a limited capacity for intrinsic self-healing. While microfracture and arthroplasty are the conventional methods for cartilage repair, these methods are unable to completely heal the damaged tissue. The need to overcome the restrictions of these therapies for cartilage regeneration has expanded the field of cartilage tissue engineering (CTE), in which novel engineering and biological approaches are introduced to accelerate the development of new biomimetic cartilage to replace the injured tissue. Until now, a wide range of hydrogels and cell sources have been employed for CTE to either recapitulate microenvironmental cues during a new tissue growth or to compel the recovery of cartilaginous structures via manipulating biochemical and biomechanical properties of the original tissue. Towards modifying current cartilage treatments, advanced hydrogels have been designed and synthesized in recent years to improve network crosslinking and self-recovery of implanted scaffolds after damage in vivo. This review focused on the recent advances in CTE, especially self-healing hydrogels. The article firstly presents the cartilage tissue, its defects, and treatments. Subsequently, introduces CTE and summarizes the polymeric hydrogels and their advances. Furthermore, characterizations, the advantages, and disadvantages of advanced hydrogels such as multi-materials, IPNs, nanomaterials, and supramolecular are discussed. Afterward, the self-healing hydrogels in CTE, mechanisms, and the physical and chemical methods for the synthesis of such hydrogels for improving the reformation of CTE are introduced. The article then briefly describes the fabrication methods in CTE. Finally, this review presents a conclusion of prevalent challenges and future outlooks for self-healing hydrogels in CTE applications.

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