Prof Sonia Antoranz Contera

Abstract:

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 behaviour in general, and relaxation times of cells of multicellular organisms in vivo with nanoscale resolution (~80 nm pixel size in this study), featuring a simple method to test the validity of the mechanical model used to interpret the data. We use this technique to image cells at the surface of living Arabidopsis thaliana hypocotyls to obtain topographical maps of storage E′ = 120–200 MPa and loss E″ = 46–111 MPa moduli as well as relaxation times τ = 2.2–2.7 µs of their cell walls. Our results demonstrate that (taken together with previous studies) cell walls, despite their complex molecular composition, display a striking continuity of simple, linear, viscoelastic behaviour across scales–following almost perfectly the standard linear solid model–with characteristic nanometer scale patterns of relaxation times, elasticity and viscosity, whose values correlate linearly with the speed of macroscopic growth. We show that the time-scales probed by dynamic AFM experiments (microseconds) are key to understand macroscopic scale dynamics (e.g. growth) as predicted by physics of polymer dynamics.

Abstract:

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 behaviour in general, and relaxation times of cells of multicellular organisms in vivo with nanoscale resolution (~80 nm pixel size in this study), featuring a simple method to test the validity of the mechanical model used to interpret the data. We use this technique to image cells at the surface of living Arabidopsis thaliana hypocotyls to obtain topographical maps of storage E' = 120-200 MPa and loss E″ = 46-111 MPa moduli as well as relaxation times τ = 2.2-2.7 µs of their cell walls. Our results demonstrate that (taken together with previous studies) cell walls, despite their complex molecular composition, display a striking continuity of simple, linear, viscoelastic behaviour across scales-following almost perfectly the standard linear solid model-with characteristic nanometer scale patterns of relaxation times, elasticity and viscosity, whose values correlate linearly with the speed of macroscopic growth. We show that the time-scales probed by dynamic AFM experiments (microseconds) are key to understand macroscopic scale dynamics (e.g. growth) as predicted by physics of polymer dynamics.

Abstract:

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 diseases, and applications as diverse as dentistry and the treatment of tuberculosis. We also examine the use of advanced smart nanostructured materials in areas such as regenerative medicine, and the controlled release of drugs and treatments. The latter is currently poised to bring ground-breaking changes in immunotherapy: the advent of 'vaccine implants' that continuously control and improve immune responses over time. With the increasingly likely prospect of ending the COVID 19 pandemic with the aid of a nanomedicine-based vaccine (both Moderna and BioNTech/Pfizer vaccines are based on lipid nanoparticle formulations), we are witnessing the coming of age of nanomedicine. This makes it more important than ever to concentrate on safety: in parallel to pursuing the benefits of nanomedine, we must strengthen the continuous focus on nanotoxicology and safety regulation of nanomedicines that can deliver the medical revolution that is within our grasp.

Abstract:

DNA self‐assembly allows the construction of nanometre‐scale 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 T‐junction origami motifs and that assembly can be performed at room temperature.