Oscillatory magnetic bead rheometer for complex fluid microrheometry

Keller, M.; Schilling, Jörg; Sackmann, E.

doi:10.1063/1.1394185

Cited by 70 publications

(66 citation statements)

References 31 publications

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“…This range of forces and displacements is suitable for microrheological measurements of biopolymer networks, such as F-actin, 3,19,46 collagen, 47 or filamentous viruses. 48 Typical values of the shear modulus of these solutions range from 0.01 to 100 Pa.…”

Section: Applicability and Improvementsmentioning

confidence: 99%

“…The electronic shutter speed of the camera was set to 1 ms and could be increased to 0.1 ms to avoid blurred images. 19 With this timing performance, oscillatory displacements up to 1000 Hz could be detected using heterodyne acquisition. 28 The analog video signal was digitized and transferred to the PC memory by an 8-bit resolution frame grabber ͑PC Eye4, Eltec, Mainz, Germany͒.…”

Section: Image Acquisitionmentioning

confidence: 99%

“…Owing to this nonlinearity, when the coils are fed with an oscillatory current, the force generated on the beads is only approximately sinusoidal. 19 To overcome these limitations, our device uses permanently magnetized ferromagnetic beads. These beads can be subjected to a secondary magnetization in a weak magnetic field without rotation of magnetic domains, i.e., with no change in their magnetic moment.…”

Section: B Ferromagnetic Beadsmentioning

confidence: 99%

“…The most common systems to obtain homogeneous force fields over a wide sample area use a single pair of electromagnets to produce a magnetic gradient. 4,18,19 The homogeneity and linearity of these systems can be improved by adding a second pair of coils to superimpose a homogeneous magnetizing field onto the gradient. 20 More complex devices which apply forces in more than one dimension have been described.…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, this dependence is nonlinear and, therefore, the force generated on the beads is not proportional to the driving signal. 19 Fourth, the habitual use of superparamagnetic beads with low magnetic moment requires the generation of large gradients to reach relatively low forces. These limitations can be overcome by employing simple coaxial coils and ferromagnetic ͑or ferrimagnetic͒ beads.…”

Section: Introductionmentioning

confidence: 99%

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Oscillatory magnetic tweezers based on ferromagnetic beads and simple coaxial coils

Trepat

Grabulosa

Buscemi

et al. 2003

Review of Scientific Instruments

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We report the design and validation of simple magnetic tweezers for oscillating ferromagnetic beads in the piconewton and nanometer scales. The system is based on a single pair of coaxial coils operating in two sequential modes: permanent magnetization of the beads through a large and brief pulse of magnetic field and generation of magnetic gradients to produce uniaxial oscillatory forces. By using this two step method, the magnetic moment of the beads remains constant during measurements. Therefore, the applied force can be computed and varies linearly with the driving signal. No feedback control is required to produce well defined force oscillations over a wide bandwidth. The design of the coils was optimized to obtain high magnetic fields ͑280 mT͒ and gradients ͑2 T/m͒ with high homogeneity ͑5% variation͒ within the sample. The magnetic tweezers were implemented in an inverted optical microscope with a videomicroscopy-based multiparticle tracking system. The apparatus was validated with 4.5 m magnetite beads obtaining forces up to ϳ2 pN and subnanometer resolution. The applicability of the device includes microrheology of biopolymer and cell cytoplasm, molecular mechanics, and mechanotransduction in living cells.

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Section: Applicability and Improvementsmentioning

confidence: 99%

Section: Image Acquisitionmentioning

confidence: 99%

Section: B Ferromagnetic Beadsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Oscillatory magnetic tweezers based on ferromagnetic beads and simple coaxial coils

Trepat

Grabulosa

Buscemi

et al. 2003

Review of Scientific Instruments

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Supported Membranes with Well‐Defined Polymer Tethers—Incorporation of Cell Receptors

Purrucker¹,

Förtig²,

Jordan³

et al. 2004

ChemPhysChem

120

154

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We report the design of supported lipid membranes attached to the surface by tailored lipopolymer tethers. A series of well-defined lipopolymers were synthesized by means of living cationic polymerization of 2-methyl-2-oxazolines. The polymers were equipped with a silane coupling group on the proximal, and lipid anchors on the distal chain ends. The length of the intermediate hydrophilic polymer tether was varied (n = 14, 18, 33) to change the distance between the membrane and the substrate. Supported membranes have been prepared in two-steps. First, a suitable lipopolymer/lipid mixture was deposited by Langmuir-Blodgett transfer, and annealed to establish the covalent coupling to the surface. On the dry lipopolymer/lipid monolayer, the upper leaflet was deposited by vesicle fusion. Optimization of both preparation steps resulted in the formation of stable and defect-free membranes. Impacts of the spacer length and the lipopolymer fraction upon the lateral diffusivity of the lipids were systematically compared by fluorescence recovery after photobleaching (FRAP). First experiments on the incorporation of a large transmembrane cell receptor (integrin alpha IIb beta 2) into the polymer-tethered membrane suggested that the length of the polymer tether plays a crucial role in distribution of the proteins on the surface.

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Biomimetic F‐Actin Cortex Models

2009

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Since its first production from muscle tissue more than 65 years ago, our knowledge about actin has come a long way. While at the beginning it was identified as a muscle protein, nowadays actin is considered as one of the most important components of the cytoskeleton, playing a crucial role in cell motility, adhesion, morphology and intracellular transport processes. In vitro models have been constructed for about 20 years to gain better insight into the chemophysical and biomechanical properties of actin networks by being able to reduce and tune its complexity. The complexity of these models ranges from single actin filaments (F-actin) in interaction with actin-associated molecules and proteins, F-actin network gels to F-actin loaded vesicles to freely suspended F-actin networks in microfluidic environments. This review summarizes the development of F-actin network models and highlights their applicability towards step-by-step construction of complex cortex mimicking systems.

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Oscillatory magnetic bead rheometer for complex fluid microrheometry

Cited by 70 publications

References 31 publications

Oscillatory magnetic tweezers based on ferromagnetic beads and simple coaxial coils

Oscillatory magnetic tweezers based on ferromagnetic beads and simple coaxial coils

Supported Membranes with Well‐Defined Polymer Tethers—Incorporation of Cell Receptors

Biomimetic F‐Actin Cortex Models

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