A number of applications in nanomedicine - imaging, drug delivery or photo therapy for instance - utilize phenomena called two-photon absorption (TPA). In TPA, the simultaneous absorption of two photons excite a molecule from one state to a higher energy electronic state. TPA initially was used only as a spectroscopic tool but new applications emerged over time. Currently approved two-photon absorption-induced excitation is one of the most promising approaches in photo therapies as it increases light penetration. It enables the use of light in the tissue-transparent window (750-1000 nm), allowing deeper light penetration and reduced risk of laser hyperthermia. An uphill energy conversion through the use of two-photon absorbing chromophores and subsequent energy transfer is a promising scientific frontier.
Studies have already shown the complexity of architecture that is achievable using DNA as building blocks. For instance, nanofabrication via molecular self-assembly has already resulted in simple DNA polyhedra with connectivities of a cube, octahedron, and a tetrahedron. Platonic solids - any one of five solids whose faces are congruent regular polygons and whose polyhedral angles are all congruent - are the most efficient at enclosing large volumes. The more complex the polyhedron, the greater its ability to encapsulate cargo, because the capsule size can be maximized while keeping the pore-size of the capsule minimal. The most complex platonic solid is the icosahedron and therefore this would be most suitable for achieving cargo encapsulation. The DNA shell of such a capsule could protect vulnerable drugs from degradation by proteins until they reach their target site. It could also prevent dangerous drugs from leaking out until the capsule reaches its intended target. The DNA shell could also allow attachment to a protein that could ferry the drug-loaded capsule to a target.
Infrared (IR) detectors are used in imaging applications that include for instance medical diagnosis, environmental monitoring, space science, and security and military sensor devices. High-quality detectors require cryogenic cooling in order for the image not to be distorted by the detectors own radiation. This makes them expensive both to produce and to run. Although uncooled IR detectors are made, their resolution and image quality tend to be much lower than cooled detectors. It appears that carbon nanotubes (CNTs) could be used as novel IR detector material that would allow the fabrication of highly efficient detectors that do not require cooling. Researchers at Michigan State University have now, for the first time, experimentally demonstrated the design, manufacturing and experimental testing of an integrated nanoantenna concept for CNT based IR sensors.
Carbon nanotubes have been recognized as promising materials for catalysis, either as catalysts themselves, as catalyst additives or as catalyst supports. Researchers are particularly excited by the promise of single-walled carbon nanotubes as electrocatalysts or electron harvesting materials for electron-to-fuel conversion. Nanotubes act as catalysts when an electric current is passed through them. This enables them to donate electrons to molecules that come in contact with the reaction sites. In trying to explain carbon nanotubes' role as catalyst, scientist have long proposed that the reactive sites for catalysis can be discrete, specific sites rather then the entire sidewall of the nanotubes. But observing them directly has been challenging. A team at Cornell University has now filled in an important blank by pinpointing unique sites where the reactions take place on SWCNTs. The scientists showed that the reactions do not occur all along the tubes, but at the ends of the tubes or at defects along the tubes.
The field of printable electronics is already well established. The biggest limitation to further increasing the functionality of printed electronics devices is energy management, i.e. the space requirement and cost of batteries. Ideally, power and energy storage devices will be integrated into the manufacturing process to be printed at the same time. What is still needed to complement a further deveopment of printed electronics device technology are truly printable charge storage devices that can be easily fabricated using large-scale, solution-based, roll-to-roll processing, while still displaying good electrochemical performance. Only fully printable charge storage devices would allow for full integration into the manufacturing process of printed electronics.
A recent study has shown that nineteenth century thermodynamics can still provide useful insights into twenty-first century nanosciences; and all this can be done with pencil and paper rather than an expensive super-computer! When the size of materials approaches the nanoscale, matter begins to behave highly exotically. By shrinking the size of materials, the surface-to-volume ratio increases. Considering this, scientists can study size effects on material properties from macroscopic laws, the so-called top-down approach. In thermodynamics, the Gibb's energy concept is particularly suited to describe the liquid-solid phase transition (what we mortals call the melting temperature).
There is a slowly growing body of work that investigates the toxicity of synthesized nanoparticles to plants, aquatic invertebrates, algae, bacteria and different cell lines and we have been covering this topic in previous Spotlights as well as our nanoRISK newsletter. Although the potential negative effects of nanoparticles on organisms and the environment have raised concerns, limited studies so far have examined the difference between nanoparticles and bulk particles with the same chemical composition and mineral phase, or addressed the toxicity of dissolved metal ions from the nanoparticles. In new work by scientists at the University of Massachusetts, the toxicity of bulk oxide particles and the released ions were assessed along with four oxide nanoparticles, which clearly showed that size matters.
Cancer researchers are therefore experimenting with nanoparticles as both contrast agent and drug carrier capable of pinpointing and destroying individual cancer cells. Targeted nanoparticles consist of a metallic or organic core conjugated with a biomolecule of interest. To be able to navigate nanoparticles to a desired target (i.e. a specific cancer cell), they need the property of specific target recognition. Depending on the type of cancer that is to be targeted, researchers choose biomolecules that show high affinity toward these specific tumor cells. Think of these biomolecules as a navigation aid to transport nanoparticles to the cancerous site or organ of interest. As part of their overall goal of developing target-specific gold nanoparticles for treatment of cancers, scientists at the University of Missouri have carried out a systematic investigation on the design and development of targeted gold nanorods.