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Micro & Nano Letters, IET

Issue 5 • Date May 2011

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Displaying Results 1 - 10 of 10
  • Editorial

    Page(s): 289 - 291
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (100 KB)  

    Mechanical factors play important roles in the regulation of various biological processes, such as gene expression, adhesion, migration, cell fate, and tissue homeostasis. Compared with the effect of biochemical factors, however, the extent and importance of mechanical factors are under explored. View full abstract»

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  • Hybridised functional micro- and nanostructure for studying the kinetics of a single biomolecule

    Page(s): 292 - 295
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (306 KB)  

    In this Letter, the nanoporous anodic alumina membranes (nanoPAAM) were first fabricated by the two-step anodic oxidisation method, and then based on these nanoPAAM master molds, polymer polymethylmethacrylate nanopillars with controllable heights and diameters were achieved by the direct casting method. Subsequently, combined with the ultraviolet lithography or electron beam lithography, a kind of useful platform of microfluidic channel that was embedded with nanopillar arrays was achieved. Finally, the transferring processes of DNA molecules around the entrance of the hybrid channel were monitored with an epi-fluorescence microscopy and electron multiplying charge coupled device camera in real time. The hybrid structure of microchannel with nanopillar arrays provides critical advantages when using the fluorescent microscopy to detect the dynamics of single DNA molecules. View full abstract»

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  • Quantitative analyses of changes in intracellular calcium ion concentrations under flow-induced mechanical stimuli utilising a microchip

    Page(s): 296 - 300
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (525 KB)  

    The authors use quantitative engineering methods to investigate changes in intracellular calcium ion concentrations ([Ca2+]i) under various flow-induced shear stresses utilising a microchip. MG-63 cells were seeded onto microchannels in a chip made of polydimethylsiloxane. A commercially available gear pump was utilised to induce and control the shear stress for up to 20 min. The temperature was maintained at 35±1°C using a computer-controlled heating jacket. Five types of flow patterns, each of which consisted of equal stimulation and rest intervals (50, 100, 150 and 200 s for stimulation, rest and steady flow) were tested. Each interval produced different patterns indicating the [Ca2+]i. Various engineering parameters were extracted from the [Ca2+]i signals recorded from a single cell after filtering to reduce background noise, including the peak to peak interval, trends in the changes of the peak values based on an exponential function and the ratio of stimulation energy to [Ca2+]i. The results indicate that this protocol can be used to analyse [Ca2+]i and related cellular responses to shearing stresses. View full abstract»

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  • Leukocyte rolling on engineered nanodot surfaces

    Page(s): 301 - 305
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (300 KB)  

    Leukocyte rolling on the blood vessel wall represents the first step in the process of inflammation. In this study, nanofabricated substrates were designed with two different sets of feature size and spacing to mimic the expected distribution of discrete molecular adhesion patches on the surfaces of endothelial cells lining the blood vessel wall. P-selectin was attached to these nanopatterned dots, and the rolling behaviour of HL60 cells was analysed as a function of wall shear stress. When wall shear stress was less than 1 dyne/cm2, rolling velocity was independent of substrate patterning. However, when wall shear stress was higher than 2 dyne/cm2, rolling velocity was increased on the patterned substrates compared with the unpatterned sample, and rolling velocity increased with nanodot spacing distance. The influence of pattern spacing on the waiting time, the duration of zero-velocity pauses during rolling, also increased for wall shear stresses greater than 2 dyne/cm2. Additionally, the variance of instantaneous rolling velocities increased among substrates when the shear stress was greater than 6 dyne/cm2, indicating that the spatial arrangement of the nanodot pattern influenced not only the average velocity with which the cells rolled but also the saltatory nature of rolling. These results suggest that nanodot substrates represent a tool to investigate the biophysical and biochemical mechanisms regulating dynamic adhesion of leukocytes to the blood vessel wall. View full abstract»

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  • Non-contact force sensing for real-time stressing of biological cells

    Page(s): 306 - 310
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (336 KB)  

    Mechanical force sensing is an important and integral component in the study of the viscoelastic properties of biological cells. In this study, a vision-based non-contact force sensing technique for real-time stressing of biological cells by a vision-guided robotic micromanipulation system is introduced. The system is capable of providing real-time external mechanical stressing on biological cells with a predefined profile and estimating the cell membrane deformation using the proposed cell strain model. One of the phenomena manifesting the viscoelastic properties of cells is the gradual reduction of reaction force in the compressive stress under cyclic loading. The applied force with respect to the cell membrane strain and the number of stressing cycles is modelled and validated by different zebrafish embryos. The experimental results show that the proposed force model can estimate the reaction force of cell membrane with the average maximum error of 10.07%. View full abstract»

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  • Quantifying growth mechanics of living, growing plant cells in situ using microbotics

    Page(s): 311 - 316
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (515 KB)  

    Plant cell growth is a fundamental process during plant development and the developmental biology society has studied cell growth from various aspects using physiological, biochemical, genetic, mathematical and modelling approaches. Recent advances in the field of biology demonstrate a need for investigation and quantification of the mechanics of growth at individual cellular levels. Here, we describe a microrobotic system capable of performing automated mechanical characterisation of living plant cells in situ as these cells proliferate and grow. The microrobotic measurement system employs a single-axis capacitive MEMS microforce sensor, a multi-axis positioning system with position feedback, a high-resolution optical microscope and a custom-user interface for the guiding of the automated measurement process. The system has been applied to measure mechanical properties of Lilium pollen tubes approximately 20--m wide. The measurements were performed in growth medium, and the observed growth rate of the pollen tubes is about 20--m per minute. For the mechanical characterisation of pollen tubes, nano-Newton level loads and nanometric indentations are applied. The force-deformation data obtained show a difference in stiffness from the tip to the apex demonstrating that the developed measurement system is a promising tool for better understanding the mechanics of plant cell growth. View full abstract»

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  • Calibrated micropost arrays for biomechanical characterisation of cardiomyocytes

    Page(s): 317 - 322
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (439 KB)  

    The study of biomechanics of isolated cardiomyocytes can allow us to understand the cardiac function and disease development in the absence of viscoelastic or contractile properties of the surrounding tissue. However, popular techniques such as micropipettes and carbon fibre-based measurements require serial, single-cell measurements and limit the amount of data passing through a system or process. The authors utilise elastomer micropost arrays microfabricated by a replica molding technique for precise and quantitative force measurements of cardiomyocytes with the potential for high throughput. The authors also present a calibration system using a piezoresistive force sensor and video-analysis technique to improve the resolution and validate the analysis of these low-force measurements. Calibrated microposts arrays are applied to measure the contractile forces of rat neonatal cardiomyocytes. Using image processing, the contractile forces for a sample of cardiomyocytes are extracted. It was found that isolated rat neonatal myocytes generate 39 ± 5 nN average contractile force per post and an integrated axial contractile force of 189 ± 20 nN, which is four times smaller than isolated adult Wistar rat cardiomyocytes and 30 times smaller than isolated adult rat cardiomyocytes. With calibration and quantitative image analysis, this study demonstrates that micropost systems can provide precise high-throughput test beds for myocyte mechanics using pharmacologic, small peptide, gene therapies or heart disease models. View full abstract»

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  • Effects of micropost spacing and stiffness on cell motility

    Page(s): 323 - 326
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (549 KB)  

    Microfabrication processes enable the biophysical control of cellular environments at the micro- and nanoscale. The mechanical properties of arrayed microposts have been demonstrated to influence diverse cellular functions including cell motility, yet the cellular response to changes in micropost spacing remains unclear. In this work, a microfabricated post array with variable spacing and stiffness was constructed to investigate the effects of these biophysical factors on cell motility. Over a length of 675 m, the spacing between arrayed microposts decreased from 6 to 2 m in a single direction, corresponding to an average spacing decrease of 40 nm from post-to-post. Simultaneously, the radii of 7 m-high microposts were decreased from 2 to 1 m, resulting in a decrease in micropost stiffness from 50 to 5 nN/ m, respectively. Over the course of 18 h studies, bovine aortic endothelial cells (BAECs) seeded on the microfabricated post array migrated for an average of 9.6 7.3 m in the direction of decreasing interpost spacing, opposite the direction of durotaxis. By the end of the studies, 61 of seeded BAECs exhibited displacement in the direction of decreasing interpost spacing. The experimental results suggest that the spacing between microposts can be a determinant factor of cell migration direction in the design of micro- and nanotopographic cellular platforms. View full abstract»

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  • Microfluidic devices for mechanical characterisation of single cells in suspension

    Page(s): 327 - 331
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (308 KB)  

    This Letter provides an overview of microfluidic technologies for single-cell mechanical characterisation. In particular, the most recent literature is discussed to summarise the working principles and development trend of the state-of-the-art microfluidic devices for mechanical characterisation of biological cells in suspension. The techniques are classified into constriction channel, fluid stress, optical stretcher, electro-deformation, electroporation and microfluidic pipette aspiration, according to the mechanism of mechanical stimuli. The principles are explained along with representative examples demonstrating their applications. The research highlighted in this letter has great potential in realising high-throughput single-cell mechanical characterisation. View full abstract»

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  • Opto-mechanical platforms for cell force study

    Page(s): 332 - 336
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (353 KB)  

    Microsystems are providing key advances in studying single-cell mechanical behaviours. The mechanical interaction of cells with their extracellular matrix is fundamentally important for cell migration, division, phagocytes and apoptosis. As the displacement and scales of cellular phenomena is comparable to optical wavelength, optical metrology offers superior resolution and real-time imaging capabilities to measure cell forces and subcellular behaviour as compared to its traditional counterparts. This review Letter discusses the principles, formation and methodological aspects of building opto-mechanical systems in studying cell forces. The authors report current advances of various opto-mechanical systems in studying different aspects of cell mechanics. View full abstract»

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Aims & Scope

Micro & Nano Letters offers express publication of short research papers presenting research conducted at the forefront of micro- and nanoscale science, engineering and technology, with at least one dimension ranging from a few tens of micrometres to a few nanometres.

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Meet Our Editors

Editors-in-Chief
Professor Gwo-Bin Vincent Lee
National Tsing-Hua University, Taiwan

Professor Peter Dobson
University of Oxford, UK