Volume 13 Issue 2, February 2014

The preclinical intersection of molecular imaging and gene- and cell-based therapies will enable more informed and effective clinical translation. We discuss how imaging can monitor cell and gene fate and function in vivo and overcome barriers associated with these therapies.

Nanoparticle-based imaging plays a crucial role in cancer diagnosis and treatment. Here, we discuss the modalities used for molecular imaging of the tumour microenvironment and image-guided interventions including drug delivery, surgery and ablation therapy.

Peaks of energy dissipation arising from distortions of a charge density wave have been observed by oscillating the tip of an atomic force microscope a few nanometres above a surface of a layered dichalchogenide.

Conjugated polymers with high electrical conductivity and high thermopower are now demonstrated. The electronic structure of these materials is that of a semi-metal, a previously unreported state for organic conductors.

DNA-capped nanoparticles crystallize into uniform microcrystals of Wulff polyhedra when cooled slowly through the melting temperature of the DNA linkers.

Detection of a wide range of tumours remains a challenge in cancer diagnostics. By exploiting changes in the tumour microenvironment, a pH-responsive polymeric nanomaterial enables ultrasensitive tumour-specific imaging in many types of cancer.

Alongside their beneficial effects within the innate immune system, macrophages can also play a detrimental role in some disease settings. This Review discusses the range of nanoparticles that are known to target macrophages and hence, are able to act as imaging agents in cancer, atherosclerosis, myocardial infarction, aortic aneurysm, diabetes and other inflammatory conditions.

Metamaterials are artificially fabricated materials that allow for the control of light and acoustic waves in a manner that is not possible in nature. This Review covers the recent developments in the study of so-called metasurfaces, which offer the possibility of controlling light with ultrathin, planar optical components.

The generation and manipulation of single photons is important for quantum information and metrology. Highly bright and stable single-photon sources are now identified in silicon carbide, a wide-bandgap semiconductor widely used for photonic and electronic devices.

Lanthanide-doped nanocrystals can be used to upconvert infrared radiation into visible light, and are thought to be promising for a range of photonic and biological imaging applications. It is now shown that the upconversion efficiency can be improved by appropriately clustering the lanthanide ions on different structural sublattices.

The interplay between the electronic and magnetic degrees of freedom in multiferroic materials offers promise for a range of applications. Now, a technique for imaging the magnetoelectric domains directly is developed, and demonstrated on the hexagonal manganite ErMnO₃.

Understanding the thermal transport properties of superlattice structures is relevant to a number of possible practical applications. Now, the scattering of phonons in oxide superlattices is shown to undergo a crossover from an incoherent to a coherent regime, which in turn strongly alters their thermal behaviour.

The friction of surfaces in relative motion and separated by a few nanometres is thought to be dominated by electronic effects. It is now found that the friction sensed by an AFM tip oscillating above a NbSe₂ surface takes the form of giant dissipation peaks, and that the peaks are related to a hysteresis cycle where the oscillating tip locally pumps 2π slips in the phase of a charge-density wave.

Topological crystalline insulators are characterized by metallic states originating from crystal symmetries. A transistor device that takes advantage of the quantum properties of the topological crystalline insulating materials SnTe and Pb_1−xSn_xSe(Te) is now proposed.

Resolving the internal structure of water molecules adsorbed on solid surfaces is challenging. Submolecular-resolution imaging of individual water monomers and tetramers on NaCl(001) films supported by a Au(111) substrate is now reported. The molecular orbitals of adsorbed water were directly visualized, which lead to the discrimination between the orientation of the monomers and the tetramers H-bond directionality.

Although it has been shown that engineering of conducting polymers such as poly(3,4-ethyldioxythiophene) can improve the Seebeck coefficient and the figure of merit ZT of these materials, the mechanisms underlying this improved thermoelectric behaviour are still not fully understood. It is now reported that the band structure of semicrystalline films of these bipolaronic polymers, resembling that of inorganic semi-metals used for thermoelectric applications, can explain these findings.

Spermine—a polyamine found in eukaryotic cells—mediates the assembly of taxol-stabilized microtubules into hexagonally packed bundles. It is now shown with electron microscopy and small-angle X-ray scattering that at higher concentrations of spermine the bundles disassemble and then reassemble into inverted tubulin tubules that expose the inner surface of the precursor microtubules, and that this results from spermine triggering a straight-to-curved conformation transition in the taxol-stabilized tubulin oligomers.

The imaging of tumours is challenging because of the wide range of different cancers. Now, the rapid detection of tumours, independent of type, is achieved using a nonlinear amplification strategy that employs ultrasensitive pH-responsive fluorescent nanoparticles that illuminate within tumour neovasculature or in response to the tumour’s acidic extracellular environment.

Imaging intracellular compartments, cells and tissues enables more accurate diagnosis and treatment of disease. In this focus issue we highlight the latest developments and clinical translation of materials-based technologies for imaging cells or the disease microenvironment with the promise of improved therapeutic outcomes.