Volume 12 Issue 11, November 2013

Poorly ordered films of conjugated polymers that show high charge mobility recently challenged the idea that disorder is detrimental for electrical conduction. Systematic studies now reveal that long polymeric chains can bridge small crystalline domains thus supporting charge transport on length scales relevant for device operation.

Cells can sense their environment by applying and responding to mechanical forces, yet how these forces are transmitted through the cell's cytoskeleton is largely unknown. Now, a combination of experiments and computer simulations shows how forces applied to the cell cortex are synergistically shared by motor proteins and crosslinkers.

Advances in photochemistry have profoundly impacted the way in which biology is studied. Now, a photoactivated enzymatic patterning method that offers spatiotemporal control over the presentation of bioactive proteins to direct cells in three-dimensional culture significantly expands the available chemical toolbox.

The discovery of a ferroelectric-like structural transition in metallic LiOsO₃ identifies a new class of materials with unconventional properties, providing an exotic playground for theorists and experimentalists.

Cancer nanomedicines approved so far minimize toxicity, but their efficacy is often limited by physiological barriers posed by the tumour microenvironment. Here, we discuss how these barriers can be overcome through innovative nanomedicine design and through creative manipulation of the tumour microenvironment.

Many materials-based therapeutic systems have reached the clinic or are in clinical trials. Here we describe materials design principles and the construction of delivery vehicles, as well as their adaptation and evaluation for human use.

Therapeutics based on small interfering RNA (siRNA), which in principle are able to reversibly silence any gene of interest, are under development for the treatment of cancers, viral infections, hereditary disorders and many other diseases. This Review discusses the biological challenges that siRNA delivery materials aim to overcome, as well as the most clinically advanced classes of siRNA delivery systems, including cyclodextrin–polymer nanoparticles, lipid nanoparticles and siRNA conjugates.

The clinical application of vaccines has expanded from infectious diseases to cancer, enhancing our vision of how the immune system can be used to prevent and treat disease. This Review highlights recent developments, clinical successes and future challenges in the design of prophylactic, therapeutic and tolerance-inducing synthetic vaccines with inspiration from the natural immune system.

Nanoscale materials that deliver drugs in response to specific stimuli offer enhanced control of the drugs' release profile and distribution. This Review provides a comprehensive discussion of progress during the past five years in the design of nanoscale systems that can respond to exogenous stimuli such as temperature or variations in light or magnetic-field intensities, or to endogenous stimuli such as redox gradients or changes in pH or enzyme concentration.

The use of macroscopic depots to deliver drugs — including small molecules, protein and cells — at the desired treatment site by using a carrier whose physical and chemical properties control the presentation of the drug increases drug effectiveness and reduces side effects. This Review discusses the advantages of macroscopic drug-delivery systems, the associated mechanisms of spatiotemporal control of drug presentation, and the design and use of multifunctional macroscopic drug-delivery devices.

The interplay between magnetism and superconductivity in copper oxide superconductors has been a topic of intense research. Now, a systematic resonant inelastic X-ray scattering study of strontium-doped lanthanum cuprate shows that high-energy magnetic excitations persist over a wide doping range.

Although metals cannot be ferroelectric in the strict sense of the term, it has long been predicted that they can undergo structural transitions that share similarities with ferroelectricity. LiOsO₃ is now shown to be an experimental realization of such a ferroelectric-like metal.

Sodium cobaltate has latterly received attention due to its appealing thermoelectric properties. By combining inelastic X-ray and neutron scattering results with detailed first-principles calculations, it is now shown that low-energy rattling modes of sodium ions within multi-vacancy clusters play a central role in determining the low thermal conductivity of this material.

The nonlinear response of a weak electrolyte to an applied electric field is known as the Wien effect. This is now simulated on a lattice Coulomb gas, therefore providing a platform for investigating system-specific corrections to the firmly established theory accounting for it.

The recent demonstration that highly disordered polymer films can transport charges as effectively as polycrystalline semiconductors has called into question the relationship between structural order and mobility in organic materials. It is now shown that, in high-molecular-weight polymers, efficient charge transport is allowed due to a network of interconnected aggregates that are characterized by short-range order.

The relative displacement of conducting molecules influences their electronic coupling and therefore the charge-transport properties of organic thin films. Electron diffraction patterns now reveal the dominant lattice vibrational modes in organic semiconductors with subnanometre precision and help predict the electronic behaviour of these materials.

Although rechargeable lithium–air batteries are receiving significant attention because of their high theoretical specific energy, carbon cathodes that are currently used decompose during oxidation and promote electrolyte decomposition on cycling. A titanium carbide-based cathode is now shown to reduce side-reactions, and exhibits enhanced reversible formation and decomposition of Li₂O₂.

Low-temperature redox reactions in solids resulting in no thermomechanical degradation can be used to enhance the performance and lifetime of energy devices. Rapid and reversible redox activity has now been demonstrated at temperatures as low as 200 °C in both epitaxially stabilized oxygen-vacancy-ordered SrCoO_2.5 and thermodynamically unfavourable perovskite SrCoO_3−δ single-crystalline thin films.

Cells can sense and respond to their environment through mechanical forces. However, how the cell’s cytoskeleton transmits forces and how cytoskeletal proteins respond to forces is largely unknown. Now, a combination of mechanical perturbations and multiscale modelling offers insights into the molecular mechanisms behind the observed variations in the accumulation kinetics of the involved proteins in response to different types of deformation.

Patterning physiologically relevant proteins in three-dimensional hydrogels without affecting the activity and stability of the proteins has been difficult. Now, by using enzymatic crosslinking reactions, in situ control over the phototriggered immobilization of virtually any desired protein in a synthetic hydrogel is demonstrated. The approach can be used to manipulate cells, as demonstrated by the three-dimensional control of the invasion of mesenchymal stem cells within poly(ethylene glycol) hydrogels.

The design and use of biocompatible materials to parcel up and deliver drugs to specific locations in the human body is at the forefront of biomedical research. The collection of articles in this Insight discusses the latest advances and current challenges in the design of materials for the delivery of therapeutics, with a focus on clinical translation.