Nanoscale & Nanoscale Advances Blog

Radiolabelling of core–shell and dumbbell-like nanoparticles

Bi-modal imaging agents are becoming more popular as they can be used to overcome limitations of single imaging modalities. In this work, radiolabelling of gold containing magnetic nanoparticles (Fe₃O_4-Au) with a nuclear isomer of technetium (^99mTc), a commonly used radionuclide for clinical photon emission computed tomography (SPECT), was assessed using two different methods.  In the first approach, Fe₃O_4-Au core-shell nanoparticles were coated with ligands containing thiol groups to bind to gold and chelator groups for [^99mTc(CO)₃]⁺. In the second approach, ^99mTc containing ligands were first synthesised, then attached to gold on Fe₃O_4-Au dumbbell-like nanoparticles. Both synthetic routes were successful in providing a sufficient radiochemical yield on the surface of magnetic nanoparticles, and are ideal candidates as dual magnetic resonance imaging MRI/SPECT imaging agents. In future studies, the authors plan to use the radiolabelled magnetic particles for bimodal imaging of tumours, through attachment of cancer-specific targeting vectors.

^99mTc radiolabelling of Fe₃O₄–Au core–shell and Au–Fe₃O₄ dumbbell-like nanoparticles
M. Felber and R. Alberto
Nanoscale, 2015, 7, 6653-6660. DOI: 10.1039/C5NR00269A

Dr Mike Barrow is a guest web writer for the Nanoscale blog. He currently works as a Postdoctoral Researcher at the University of Liverpool.

Visual image after EBL treatment, corresponding Raman spectroscopy map of a graphene flake and Raman spectra recorded at different spots on the sample.

Research articles on graphene have been numerously been presented throughout the last decade, indicating the promising future of this material. However, bridging the gap between laboratory research and industrial application remains difficult due to missing specialized large-scale production equipment.

A new article recently published by A. Caglinani et al. introduces an electron beam-based patterning technique using solely widely available clean-room equipment. Based on the findings of the paper, graphene structuring could become a more widespread processing technique.

The researchers developed a patterning process utilizing an industry-standard electron beam lithography system and a standard oven to achieve a resolution of 40 nm.

In the first step, a graphene layer is irradiated by the electron beam which locally generates defects within the crystal lattice. The damage was found by the researchers to be spatially confined to the exposed areas, thus allowing for arbitrary patterns.

The second step comprised etching the irradiated areas by means of hot air at atmospheric pressure. The high defect density (e.g. dangling bonds) induced by the electron beam lead to a large difference in the etch rate compared to the unmodified areas. By exposing the samples for 16 min at 435°C to air, the previously irradiated areas were selectively etched.

In conclusion, the presented process can be used to easily structure graphene layers for future application without the need for specialized equipment. According to the authors, future improvements could reduce the minimum feature size further.

Sebastian Axmann is a guest web-writer for the Nanoscale blog. His interests comprise manufacturing and metrology of nanostructures as well as their usage in current semiconductor devices. He also posts links to interesting research articles on Twitter: @SebastianAxmann.

Viruses are highly complex biological nanostructures.  This complexity has renewed an interest in viruses from the perspective of fundamental physics at the nanoscale. An understanding of the mechanical properties of virus particles at the molecular level can reveal information regarding stiffness, intrinsic elasticity, structural strength and resistance to mechanical fatigue.  This information can provide a basis for researchers to engineer virus-based nanoparticles as nanodevices/ nanocontainers for different biotechnological applications.

The MVM virion.

Castellanos and co-workers have endeavoured to understand the conformational stability and dynamics of the minute virus of mice (MVM), a small ~ 25 nm virus particle, which serves as a model system to understand some of the mechanical properties of viruses. To this end, the researchers have investigated the linkage between the DNA-mediated increase in mechanical stiffness and heat-induced structural changes, and a quantitative relationship between mechanical elasticity and conformational dynamics in MVM nanoparticles.

The researchers used a combination of transmission electron microscopy (TEM) and atomic force microscopy (AFM) for determining the thermal inactivation behaviour and the mechanical stiffness of the viruses, respectively.  By utilizing these techniques, the researchers have deduced that infectious MVM particles may have evolved architectural functions that increase their survival in thermally stressed environments.

This proof-of-principle study has demonstrated that nanoscale features of virus nanoparticles can be probed analytically using AFM and the elucidation of these features have future impact in the field of protein engineering.

Dr Lee Barrett is a guest web writer for the Nanoscale blog. Lee is currently a postdoctoral researcher in the Centre for Molecular Nanometrology at the University of Strathclyde. His research is currently focused on the development of nanoparticle-based sensors and surface enhanced Raman scattering (SERS). Follow him on twitter @L_Bargie.

DNA origami machine components

DNA origami is an emerging field of nanotechnology that exploits the unique base-pairing capabilities of the DNA bases to produce complex and mechanically stiff self-assembled nanoscale geometries. Recently, DNA origami has found uses in applications such as single molecule sensing, drug delivery and templating molecular components.

This review, by researchers from Ohio State University, sets out to explore the mechanical nature of DNA nanostructures in order to understand how these structures will respond to physical interactions. The review covers three major areas of progress, including measuring and designing mechanical properties of DNA nanostructures, designing complex nanostructures based on imposed mechanical stresses and, finally, designing and controlling structurally dynamic nanostructures.

For researchers interested in the future possibilities of DNA origami, this review should provide an insightful first stop for discussing the mechanical design of DNA nanostructures.

Mechanical design of DNA nanostructures
Carlos E. Castro, Hai-Jun Su, Alexander E. Marras, Lifeng Zhou and Joshua Johnson
Nanoscale, 2015, Advance Article. DOI: 10.1039/C4NR07153K

Dr Lee Barrett is a guest web writer for the Nanoscale blog. Lee is currently a postdoctoral researcher in the Centre for Molecular Nanometrology at the University of Strathclyde. His research is currently focused on the development of nanoparticle-based sensors and surface enhanced Raman scattering (SERS). Follow him on twitter: @L_Bargie