Sonia Contera | University of Oxford (original) (raw)
Papers by Sonia Contera
Small solid-state devices are candidates for accelerating biomedical assays/drug discovery, howev... more Small solid-state devices are candidates for accelerating biomedical assays/drug discovery, however their potential remains unfulfilled. Here, we demonstrate that graphene-field effect transistors (FET) can be used to successfully detect the key molecular events underlying viral infections and the effect of antiviral drugs. Our device success is achieved by bio-mimicking the host-cell surface during an influenza infection at the graphene channel. In-situ AFM confirms the biological interactions at the sialic acid-functionalized graphene: viral hemagglutinin (HA) binds to sialic acid, and neuraminidase (NA) reacts with the sialic acid-HA complex. The graphene-FET detects HA binding to sialic acid, and NA cleavage of sialic acid. The inhibitory effect of the drug “zanamivir” on NA-sialic acid interactions is monitored in real-time; the reaction rate constant of NA-sialic acid reaction was successfully determined. We demonstrate that graphene-FETs are powerful platforms for measurement...
Unravelling the specific growth dynamics of key tissues and organs is fundamental to understand h... more Unravelling the specific growth dynamics of key tissues and organs is fundamental to understand how multicellular organisms orchestrate their different growth programmes. In plants, the secondary growth (thickening) of stems and roots provides the mechanical support that plants need to achieve their developmental potential. We used conventional anatomical and microscopy techniques, image-processing software, and quantitative analysis to understand and mathematically describe the growth dynamics of the early developmental stages of secondary xylem (the main tissue developed during secondary growth). Results show that such early developmental stages are characterized by exponential expansion of secondary xylem in 3D in the form of an inverted cone, with a power law that describes the relationship between the area of the base and the longitudinal progression (height) of the growing secondary xylem cone over time with a scaling exponent of 2/5: the signature of allometric growth. Our wo...
Unravelling the specific growth dynamics of key tissues and organs is fundamental to understand h... more Unravelling the specific growth dynamics of key tissues and organs is fundamental to understand how multicellular organisms orchestrate their different growth programmes. In plants, the secondary growth (thickening) of stems and roots provides the mechanical support that plants need to achieve their developmental potential. We used conventional anatomical and microscopy techniques, image-processing software, and quantitative analysis to understand and mathematically describe the growth dynamics of the early developmental stages of secondary xylem (the main tissue developed during secondary growth). Results show that such early developmental stages are characterized by exponential expansion of secondary xylem in 3D in the form of an inverted cone, with a power law that describes the relationship between the area of the base and the longitudinal progression (height) of the growing secondary xylem cone over time with a scaling exponent of 2/5: the signature of allometric growth. Our wo...
Unravelling the specific growth dynamics of key tissues and organs is fundamental to understand h... more Unravelling the specific growth dynamics of key tissues and organs is fundamental to understand how multicellular organisms orchestrate their different growth programmes. In plants, the secondary growth (thickening) of stems and roots provides the mechanical support that plants need to achieve their developmental potential. We used conventional anatomical and microscopy techniques, image-processing software, and quantitative analysis to understand and mathematically describe the growth dynamics of the early developmental stages of secondary xylem (the main tissue developed during secondary growth). Results show that such early developmental stages are characterized by exponential expansion of secondary xylem in 3D in the form of an inverted cone, with a power law that describes the relationship between the area of the base and the longitudinal progression (height) of the growing secondary xylem cone over time with a scaling exponent of 2/5: the signature of allometric growth. Our wo...
The zip folder PNAS_paper contains the original ibw files for Figs 2, 3 and S1 for the recently a... more The zip folder PNAS_paper contains the original ibw files for Figs 2, 3 and S1 for the recently accepted paper: Al-Rekabi Z & Contera S. 2018. PNAS. (accepted).
Nature Reviews Materials, 2021
The future of our species and planet hinges on our scientific creativity to tackle future challen... more The future of our species and planet hinges on our scientific creativity to tackle future challenges. However, the trust of the public in scientific processes needs to be earned and kept, which will require inclusive, self-reflecting, honest and inspiring science communication.
Unravelling the specific growth dynamics of key tissues and organs is fundamental to understand h... more Unravelling the specific growth dynamics of key tissues and organs is fundamental to understand how multicellular organisms orchestrate their different growth programmes. In plants, the secondary growth (thickening) of stems and roots provides the mechanical support that plants need to achieve their developmental potential. We used conventional anatomical and microscopy techniques, image-processing software, and quantitative analysis to understand and mathematically describe the growth dynamics of the early developmental stages of secondary xylem (the main tissue developed during secondary growth). Results show that such early developmental stages are characterized by exponential expansion of secondary xylem in 3D in the form of an inverted cone, with a power law that describes the relationship between the area of the base and the longitudinal progression (height) of the growing secondary xylem cone over time with a scaling exponent of 2/5: the signature of allometric growth. Our work constitutes a starting point for future modelling of secondary xylem in particular and secondary growth in general.
Emerging Topics in Life Sciences, 2020
The 1980s mark the starting point of nanotechnology: the capacity to synthesise, manipulate and v... more The 1980s mark the starting point of nanotechnology: the capacity to synthesise, manipulate and visualise matter at the nanometre scale. New powers to reach the nanoscale brought us the unprecedented possibility to directly target at the scale of biomolecular interactions, and the motivation to create smart nanostructures that could circumvent the hurdles hindering the success of traditional pharmacological approaches. Forty years on, the progressive integration of bio- and nanotechnologies is starting to produce a transformation of the way we detect, treat and monitor diseases and unresolved medical problems [ 1]. While much of the work remains in research laboratories, the first nano-based treatments, vaccines, drugs, and diagnostic devices, are now receiving approval for commercialisation and clinical use. In this special issue we review recent advances of nanomedical approaches to combat antibiotic resistance, treatment and detection of cancers, targeting neurodegerative disease...
The shapes of living organisms are formed and maintained by precise control in time and space of ... more The shapes of living organisms are formed and maintained by precise control in time and space of growth, which is achieved by dynamically fine-tuning the mechanical (viscous and elastic) properties of their hierarchically built structures from the nanometer up. Most organisms on Earth including plants grow by yield (under pressure) of cell walls (bio-polymeric matrices equivalent to extracellular matrix in animal tissues) whose underlying nanoscale viscoelastic properties remain unknown. Multifrequency atomic force microscopy (AFM) techniques exist that are able to map properties to a small subgroup of linear viscoelastic materials (those obeying the Kelvin-Voigt model), but are not applicable to growing materials, and hence are of limited interest to most biological situations. Here, we extend existing dynamic AFM methods to image linear viscoelastic behavior in general, and relaxation times of cells of multicellular organisms in vivo with nanoscale resolution, featuring a simple m...
Angewandte Chemie, 2020
DNA self-assembly allows the construction of nanometrescale structures and devices. Structures wi... more DNA self-assembly allows the construction of nanometrescale structures and devices. Structures with thousands of unique components are routinely assembled in good yield. Experimental progress has been rapid, based largely on empirical design rules. Here we demonstrate a DNA origami technique designed as a model system with which to explore the mechanism of assembly. The origami fold is controlled through single-stranded loops embedded in a double-stranded DNA template and is programmed by a set of double-stranded linkers that specify pairwise interactions between loop sequences. Assembly is via T-junctions formed by hybridization of single-stranded overhangs on the linkers with the loops. The sequence of loops on the template and the set of interaction rules embodied in the linkers can be reconfigured with ease. We show that a set of just two interaction rules can be used to assemble simple Tjunction origami motifs and that assembly can be performed at room temperature.
Applied Materials Today, 2020
Polymeric magnetic spherical microparticles are employed as sensors/actuators in lab-on-a-chip ap... more Polymeric magnetic spherical microparticles are employed as sensors/actuators in lab-on-a-chip applications, small-scale robotics and biomedical/biophysical assays. Achieving controlled stable motion of the microparticles in a fluid environment using low intensity magnetic fields is necessary to achieve much of their technological potential; this requires that the microparticle is magnetically anisotropic, which is difficult to achieve in spheres. Here we have developed a simple method to synthesise anisotropic ellipsoidal microparticles (average eccentricity 0.60 ± 0.14) by applying a magnetic field during synthesis, using a nanocomposite of polycaprolactone (PCL) with Fe 3 O 4 nanowires. The "microellipsoids" are thoroughly characterised using optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX). Their suitability for magnetically controlled motion is demonstrated by analysing their rotation in low magnetic fields (0.1, 1, 5, 10 and 20 mT) at varying rotational frequencies (1Hz and 5Hz). The microellipsoids are able to follow smoothly and continuously the magnetic field, while commercial spherical particles fail to continuously follow the magnetic field, and oscillate backwards and forwards resulting in much lower average angular speeds. Furthermore, only 23% of commercial particles analysed rotated at 1 Hz and 26% at 5 Hz, whereas 77% of our ellipsoidal particles rotated at 1 Hz, and 74% did at 5 Hz.
Scientific Reports, 2019
Cell lipid membranes are the primary site of irreversible injury during freezing/thawing and cryo... more Cell lipid membranes are the primary site of irreversible injury during freezing/thawing and cryopreservation of cells, but the underlying causes remain unknown. Here, we probe the effect of cooling from 20 °C to 0 °C on the structure and mechanical properties of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) bilayers using atomic force microscopy (AFM) imaging and AFM-based nanoindentation in a liquid environment. The Young’s modulus of elasticity (E) at each temperature for DPPC was obtained at different ionic strengths. Both at 20 mM and 150 mM NaCl, E of DPPC bilayers increases exponentially –as expected–as the temperature is lowered between 20 °C and 5 °C, but at 0 °C E drops from the values measured at 5 °C. Our results support the hypothesis that mechanical weakening of the bilayer at 0 °C is produced by structural changes at the lipid-fluid interface.
Royal Society Open Science, 2019
Unravelling the specific growth dynamics of key tissues and organs is fundamental to understand h... more Unravelling the specific growth dynamics of key tissues and organs is fundamental to understand how multicellular organisms orchestrate their different growth programmes. In plants, the secondary growth (thickening) of stems and roots provides the mechanical support that plants need to achieve their developmental potential. We used conventional anatomical and microscopy techniques, image-processing software, and quantitative analysis to understand and mathematically describe the growth dynamics of the early developmental stages of secondary xylem (the main tissue developed during secondary growth). Results show that such early developmental stages are characterized by exponential expansion of secondary xylem in three dimensions in the form of an inverted cone, with a power law that describes the relationship between the area of the base and the longitudinal progression (height) of the growing secondary xylem cone over time with a scaling exponent of 2/5: the signature of allometric ...
Journal of the Mechanical Behavior of Biomedical Materials, 2019
Alginate microbeads are extensively used in tissue engineering as microcarriers and cell encapsul... more Alginate microbeads are extensively used in tissue engineering as microcarriers and cell encapsulation vessels. In this study, we used atomic force microscopy (AFM) based indentation using 20 μm colloidal probes to assess the local reduced elastic modulus (E*) using a novel method to detect the contact point based on the principle of virtual work, to measure microbead mechanical stability under cell culture conditions for 2 weeks. The bead diameter and swelling were assessed in parallel. Alginate beads swelled up to 150 % of their original diameter following addition of cell culture media. The diameter eventually stabilized from day 2 onwards. This behaviour was mirrored in E* where a significant decrease was observed at the start of the culture period before stabilization was observed at ~ 2.1 kPa. Furthermore, the mechanical properties of freeze dried alginate beads after re-swelling them in culture media were measured. These beads displayed vastly different structural and mechanical properties compared those that did not go through the freeze drying process, with around 125 % swelling and a significantly higher E* at values over 3 kPa.
Proceedings of the National Academy of Sciences, 2018
Significance The lipid bilayer mediates a number of cellular processes including cell recognition... more Significance The lipid bilayer mediates a number of cellular processes including cell recognition, signaling, transfer of ions, adhesion, and fusion. In orchestrating these functions, the cell membrane behaves as both an elastic and a viscous material. Although the physical properties of the lipid bilayer have been extensively studied, a thorough description of the viscoelasticity of the membrane is significantly less well characterized. In our study, we utilize multifrequency atomic force microscopy (AFM) as a tool to extract quantitative viscoelastic information of a model lipid system with molar fraction inserts of cholesterol (Chol). Using this approach, we provide evidence that the lipid bilayer appears to exhibit both elastic and viscous properties, an important aspect in its role in mechanotransduction.
Nature communications, Jan 4, 2018
Topological insulators exhibit a metallic surface state in which the directions of the carriers&#... more Topological insulators exhibit a metallic surface state in which the directions of the carriers' momentum and spin are locked together. This characteristic property, which lies at the heart of proposed applications of topological insulators, protects carriers in the surface state from back-scattering unless the scattering centres are time-reversal symmetry breaking (i.e. magnetic). Here, we introduce a method of probing the effect of magnetic scattering by decorating the surface of topological insulators with molecules, whose magnetic degrees of freedom can be engineered independently of their electrostatic structure. We show that this approach allows us to separate the effects of magnetic and non-magnetic scattering in the perturbative limit. We thereby confirm that the low-temperature conductivity of SmB is dominated by a surface state and that the momentum of quasiparticles in this state is particularly sensitive to magnetic scatterers, as expected in a topological insulator.
Nature communications, Jan 15, 2018
The original version of this Article contained an error in the spelling of the author Benjamin H.... more The original version of this Article contained an error in the spelling of the author Benjamin H. Williams, which was incorrectly given as Benjamin H. Willams. This has now been corrected in both the PDF and HTML versions of the Article.
Small solid-state devices are candidates for accelerating biomedical assays/drug discovery, howev... more Small solid-state devices are candidates for accelerating biomedical assays/drug discovery, however their potential remains unfulfilled. Here, we demonstrate that graphene-field effect transistors (FET) can be used to successfully detect the key molecular events underlying viral infections and the effect of antiviral drugs. Our device success is achieved by bio-mimicking the host-cell surface during an influenza infection at the graphene channel. In-situ AFM confirms the biological interactions at the sialic acid-functionalized graphene: viral hemagglutinin (HA) binds to sialic acid, and neuraminidase (NA) reacts with the sialic acid-HA complex. The graphene-FET detects HA binding to sialic acid, and NA cleavage of sialic acid. The inhibitory effect of the drug “zanamivir” on NA-sialic acid interactions is monitored in real-time; the reaction rate constant of NA-sialic acid reaction was successfully determined. We demonstrate that graphene-FETs are powerful platforms for measurement...
Unravelling the specific growth dynamics of key tissues and organs is fundamental to understand h... more Unravelling the specific growth dynamics of key tissues and organs is fundamental to understand how multicellular organisms orchestrate their different growth programmes. In plants, the secondary growth (thickening) of stems and roots provides the mechanical support that plants need to achieve their developmental potential. We used conventional anatomical and microscopy techniques, image-processing software, and quantitative analysis to understand and mathematically describe the growth dynamics of the early developmental stages of secondary xylem (the main tissue developed during secondary growth). Results show that such early developmental stages are characterized by exponential expansion of secondary xylem in 3D in the form of an inverted cone, with a power law that describes the relationship between the area of the base and the longitudinal progression (height) of the growing secondary xylem cone over time with a scaling exponent of 2/5: the signature of allometric growth. Our wo...
Unravelling the specific growth dynamics of key tissues and organs is fundamental to understand h... more Unravelling the specific growth dynamics of key tissues and organs is fundamental to understand how multicellular organisms orchestrate their different growth programmes. In plants, the secondary growth (thickening) of stems and roots provides the mechanical support that plants need to achieve their developmental potential. We used conventional anatomical and microscopy techniques, image-processing software, and quantitative analysis to understand and mathematically describe the growth dynamics of the early developmental stages of secondary xylem (the main tissue developed during secondary growth). Results show that such early developmental stages are characterized by exponential expansion of secondary xylem in 3D in the form of an inverted cone, with a power law that describes the relationship between the area of the base and the longitudinal progression (height) of the growing secondary xylem cone over time with a scaling exponent of 2/5: the signature of allometric growth. Our wo...
Unravelling the specific growth dynamics of key tissues and organs is fundamental to understand h... more Unravelling the specific growth dynamics of key tissues and organs is fundamental to understand how multicellular organisms orchestrate their different growth programmes. In plants, the secondary growth (thickening) of stems and roots provides the mechanical support that plants need to achieve their developmental potential. We used conventional anatomical and microscopy techniques, image-processing software, and quantitative analysis to understand and mathematically describe the growth dynamics of the early developmental stages of secondary xylem (the main tissue developed during secondary growth). Results show that such early developmental stages are characterized by exponential expansion of secondary xylem in 3D in the form of an inverted cone, with a power law that describes the relationship between the area of the base and the longitudinal progression (height) of the growing secondary xylem cone over time with a scaling exponent of 2/5: the signature of allometric growth. Our wo...
The zip folder PNAS_paper contains the original ibw files for Figs 2, 3 and S1 for the recently a... more The zip folder PNAS_paper contains the original ibw files for Figs 2, 3 and S1 for the recently accepted paper: Al-Rekabi Z & Contera S. 2018. PNAS. (accepted).
Nature Reviews Materials, 2021
The future of our species and planet hinges on our scientific creativity to tackle future challen... more The future of our species and planet hinges on our scientific creativity to tackle future challenges. However, the trust of the public in scientific processes needs to be earned and kept, which will require inclusive, self-reflecting, honest and inspiring science communication.
Unravelling the specific growth dynamics of key tissues and organs is fundamental to understand h... more Unravelling the specific growth dynamics of key tissues and organs is fundamental to understand how multicellular organisms orchestrate their different growth programmes. In plants, the secondary growth (thickening) of stems and roots provides the mechanical support that plants need to achieve their developmental potential. We used conventional anatomical and microscopy techniques, image-processing software, and quantitative analysis to understand and mathematically describe the growth dynamics of the early developmental stages of secondary xylem (the main tissue developed during secondary growth). Results show that such early developmental stages are characterized by exponential expansion of secondary xylem in 3D in the form of an inverted cone, with a power law that describes the relationship between the area of the base and the longitudinal progression (height) of the growing secondary xylem cone over time with a scaling exponent of 2/5: the signature of allometric growth. Our work constitutes a starting point for future modelling of secondary xylem in particular and secondary growth in general.
Emerging Topics in Life Sciences, 2020
The 1980s mark the starting point of nanotechnology: the capacity to synthesise, manipulate and v... more The 1980s mark the starting point of nanotechnology: the capacity to synthesise, manipulate and visualise matter at the nanometre scale. New powers to reach the nanoscale brought us the unprecedented possibility to directly target at the scale of biomolecular interactions, and the motivation to create smart nanostructures that could circumvent the hurdles hindering the success of traditional pharmacological approaches. Forty years on, the progressive integration of bio- and nanotechnologies is starting to produce a transformation of the way we detect, treat and monitor diseases and unresolved medical problems [ 1]. While much of the work remains in research laboratories, the first nano-based treatments, vaccines, drugs, and diagnostic devices, are now receiving approval for commercialisation and clinical use. In this special issue we review recent advances of nanomedical approaches to combat antibiotic resistance, treatment and detection of cancers, targeting neurodegerative disease...
The shapes of living organisms are formed and maintained by precise control in time and space of ... more The shapes of living organisms are formed and maintained by precise control in time and space of growth, which is achieved by dynamically fine-tuning the mechanical (viscous and elastic) properties of their hierarchically built structures from the nanometer up. Most organisms on Earth including plants grow by yield (under pressure) of cell walls (bio-polymeric matrices equivalent to extracellular matrix in animal tissues) whose underlying nanoscale viscoelastic properties remain unknown. Multifrequency atomic force microscopy (AFM) techniques exist that are able to map properties to a small subgroup of linear viscoelastic materials (those obeying the Kelvin-Voigt model), but are not applicable to growing materials, and hence are of limited interest to most biological situations. Here, we extend existing dynamic AFM methods to image linear viscoelastic behavior in general, and relaxation times of cells of multicellular organisms in vivo with nanoscale resolution, featuring a simple m...
Angewandte Chemie, 2020
DNA self-assembly allows the construction of nanometrescale structures and devices. Structures wi... more DNA self-assembly allows the construction of nanometrescale structures and devices. Structures with thousands of unique components are routinely assembled in good yield. Experimental progress has been rapid, based largely on empirical design rules. Here we demonstrate a DNA origami technique designed as a model system with which to explore the mechanism of assembly. The origami fold is controlled through single-stranded loops embedded in a double-stranded DNA template and is programmed by a set of double-stranded linkers that specify pairwise interactions between loop sequences. Assembly is via T-junctions formed by hybridization of single-stranded overhangs on the linkers with the loops. The sequence of loops on the template and the set of interaction rules embodied in the linkers can be reconfigured with ease. We show that a set of just two interaction rules can be used to assemble simple Tjunction origami motifs and that assembly can be performed at room temperature.
Applied Materials Today, 2020
Polymeric magnetic spherical microparticles are employed as sensors/actuators in lab-on-a-chip ap... more Polymeric magnetic spherical microparticles are employed as sensors/actuators in lab-on-a-chip applications, small-scale robotics and biomedical/biophysical assays. Achieving controlled stable motion of the microparticles in a fluid environment using low intensity magnetic fields is necessary to achieve much of their technological potential; this requires that the microparticle is magnetically anisotropic, which is difficult to achieve in spheres. Here we have developed a simple method to synthesise anisotropic ellipsoidal microparticles (average eccentricity 0.60 ± 0.14) by applying a magnetic field during synthesis, using a nanocomposite of polycaprolactone (PCL) with Fe 3 O 4 nanowires. The "microellipsoids" are thoroughly characterised using optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX). Their suitability for magnetically controlled motion is demonstrated by analysing their rotation in low magnetic fields (0.1, 1, 5, 10 and 20 mT) at varying rotational frequencies (1Hz and 5Hz). The microellipsoids are able to follow smoothly and continuously the magnetic field, while commercial spherical particles fail to continuously follow the magnetic field, and oscillate backwards and forwards resulting in much lower average angular speeds. Furthermore, only 23% of commercial particles analysed rotated at 1 Hz and 26% at 5 Hz, whereas 77% of our ellipsoidal particles rotated at 1 Hz, and 74% did at 5 Hz.
Scientific Reports, 2019
Cell lipid membranes are the primary site of irreversible injury during freezing/thawing and cryo... more Cell lipid membranes are the primary site of irreversible injury during freezing/thawing and cryopreservation of cells, but the underlying causes remain unknown. Here, we probe the effect of cooling from 20 °C to 0 °C on the structure and mechanical properties of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) bilayers using atomic force microscopy (AFM) imaging and AFM-based nanoindentation in a liquid environment. The Young’s modulus of elasticity (E) at each temperature for DPPC was obtained at different ionic strengths. Both at 20 mM and 150 mM NaCl, E of DPPC bilayers increases exponentially –as expected–as the temperature is lowered between 20 °C and 5 °C, but at 0 °C E drops from the values measured at 5 °C. Our results support the hypothesis that mechanical weakening of the bilayer at 0 °C is produced by structural changes at the lipid-fluid interface.
Royal Society Open Science, 2019
Unravelling the specific growth dynamics of key tissues and organs is fundamental to understand h... more Unravelling the specific growth dynamics of key tissues and organs is fundamental to understand how multicellular organisms orchestrate their different growth programmes. In plants, the secondary growth (thickening) of stems and roots provides the mechanical support that plants need to achieve their developmental potential. We used conventional anatomical and microscopy techniques, image-processing software, and quantitative analysis to understand and mathematically describe the growth dynamics of the early developmental stages of secondary xylem (the main tissue developed during secondary growth). Results show that such early developmental stages are characterized by exponential expansion of secondary xylem in three dimensions in the form of an inverted cone, with a power law that describes the relationship between the area of the base and the longitudinal progression (height) of the growing secondary xylem cone over time with a scaling exponent of 2/5: the signature of allometric ...
Journal of the Mechanical Behavior of Biomedical Materials, 2019
Alginate microbeads are extensively used in tissue engineering as microcarriers and cell encapsul... more Alginate microbeads are extensively used in tissue engineering as microcarriers and cell encapsulation vessels. In this study, we used atomic force microscopy (AFM) based indentation using 20 μm colloidal probes to assess the local reduced elastic modulus (E*) using a novel method to detect the contact point based on the principle of virtual work, to measure microbead mechanical stability under cell culture conditions for 2 weeks. The bead diameter and swelling were assessed in parallel. Alginate beads swelled up to 150 % of their original diameter following addition of cell culture media. The diameter eventually stabilized from day 2 onwards. This behaviour was mirrored in E* where a significant decrease was observed at the start of the culture period before stabilization was observed at ~ 2.1 kPa. Furthermore, the mechanical properties of freeze dried alginate beads after re-swelling them in culture media were measured. These beads displayed vastly different structural and mechanical properties compared those that did not go through the freeze drying process, with around 125 % swelling and a significantly higher E* at values over 3 kPa.
Proceedings of the National Academy of Sciences, 2018
Significance The lipid bilayer mediates a number of cellular processes including cell recognition... more Significance The lipid bilayer mediates a number of cellular processes including cell recognition, signaling, transfer of ions, adhesion, and fusion. In orchestrating these functions, the cell membrane behaves as both an elastic and a viscous material. Although the physical properties of the lipid bilayer have been extensively studied, a thorough description of the viscoelasticity of the membrane is significantly less well characterized. In our study, we utilize multifrequency atomic force microscopy (AFM) as a tool to extract quantitative viscoelastic information of a model lipid system with molar fraction inserts of cholesterol (Chol). Using this approach, we provide evidence that the lipid bilayer appears to exhibit both elastic and viscous properties, an important aspect in its role in mechanotransduction.
Nature communications, Jan 4, 2018
Topological insulators exhibit a metallic surface state in which the directions of the carriers&#... more Topological insulators exhibit a metallic surface state in which the directions of the carriers' momentum and spin are locked together. This characteristic property, which lies at the heart of proposed applications of topological insulators, protects carriers in the surface state from back-scattering unless the scattering centres are time-reversal symmetry breaking (i.e. magnetic). Here, we introduce a method of probing the effect of magnetic scattering by decorating the surface of topological insulators with molecules, whose magnetic degrees of freedom can be engineered independently of their electrostatic structure. We show that this approach allows us to separate the effects of magnetic and non-magnetic scattering in the perturbative limit. We thereby confirm that the low-temperature conductivity of SmB is dominated by a surface state and that the momentum of quasiparticles in this state is particularly sensitive to magnetic scatterers, as expected in a topological insulator.
Nature communications, Jan 15, 2018
The original version of this Article contained an error in the spelling of the author Benjamin H.... more The original version of this Article contained an error in the spelling of the author Benjamin H. Williams, which was incorrectly given as Benjamin H. Willams. This has now been corrected in both the PDF and HTML versions of the Article.