Nanoscale & Nanoscale Advances Blog

Researchers in Korea have developed a new temperature sensing platform based on graphene oxide (GO). The sensor uses GO’s functionality as an efficient Förster resonance energy transfer (FRET) acceptor to deliver a fast optical on-off signal in response to temperature change.

The article describes how the scientists functionalised GO sheets with thermally-responsive triblock copolymers for the first time. The triblock copolymer brush was designed to contain a component for covalent grafting to GO, a thermally-responsive component and a fluorescent component. At elevated temperatures, the thermally-responsive component (poly(N-isopropylacrylamide) undergoes a conformational change that reduces the distance between the fluorophore and GO. This quenches the photoluminescence (PL) of the flurophore component.

The scientists tested a dispersion of the functionalised GO sensing platform in water.  PL spectra showed a decrease in intensity as the temperature was increased. A marked decrease in PL intensity was evident at temperatures above 32 ^oC, demonstrating an on-off switching behaviour of the sensor. The functionalised graphene oxide composites demonstrated excellent stability in water, opening up the possibility for their use as optical indicators of temperature change in biologically and environmentally compatible sensing systems.

Read the full details of this HOT Nanoscale article today:

Efficient temperature sensing platform based on fluorescent block copolymer-functionalized graphene oxide
Bumjoon Kim, Hyunseung Yang and Kwanyeol Paek
DOI: 10.1039/C3NR01486J

In this HOT Nanoscale article the authors report on the biodistribution of gold nanoparticles (Au@DTDTPA) after intravenous injection into healthy rats.

Gold nanoparticles have shown great potential as radiosensitisers for radiotherapy so the biodistribution of the nanoparticles in healthy tissues constitutes a crucial issue that must be addressed to guarantee the optimal use of these particles. Owing to the propensity of gold for absorbing X-ray photons, these nanoparticles behave as contrast agents for X-ray imaging. Moreover, Au@DTDTPA-Gd nanoparticles can be followed up by magnetic resonance imaging (MRI), since the organic shell, DTDTPA, is composed of polyaminocarboxylate ligands which are well known for entrapping gadolinium ions. Both complementary imaging modalities are well suited for monitoring the accumulation in a specific tissue or in a tumor. However scintigraphy appears better suited for a complete biodistribution study because of its greater sensitivity and the possibility to image the whole body for a duration that is compatible with the pharmacokinetics. The authors demonstrated that the replacement of the gadolinium ions by ^99mTc and ¹¹¹In ions renders the Au@DTDTPA nanoparticles suitable for the study of the biodistribution by scintigraphy. The radiolabeled gold nanoparticles (Au@DTDTPA-X, with X = ^99mTc and ¹¹¹In) exhibit high radiochemical purities and radiolabeling stabilities.

The tracking of the radiolabeled Au@DTDTPA nanoparticles by planar scintigraphy and single photon emission computed tomography (SPECT) after intravenous injection associated to the post-mortem analysis showed that these particles exhibit safe behavior: the nanoparticles are removed from the body essentially by renal clearance while no accumulation is observed in the organs (except those involved in the renal clearance (kidneys, bladder)). Moreover the physicochemical properties of Au@DTDTPA-X nanoparticles impede any reticuloendothelial system uptake as reflected by the low uptake by phagocyte-rich organs (liver and spleen).

The follow-up by at least three different imaging modalities (X-ray imaging, MRI, scintigraphy), the absence of undesirable accumulation and the removal by urine suggest Au@DTDTPA nanoparticles are very promising for in vivo applications, especially for image-guided radiotherapy.

Read this HOT article in full today:

The biodistribution of gold nanoparticles designed for renal clearance
Christophe Alric, Imen Miladi, David Kryza, Jacqueline Taleb, Francois Lux, Rana Bazzi, Claire Billotey, Marc Janier, Pascal Perriat, Stéphane Roux and Olivier Tillement
DOI: 10.1039/C3NR00012E

Scientists based in The Netherlands report a series of novel reversible photoswitches based on diarylethene embedded in a matrix of dodecanethiol on Au(111). The authors used scanning tunneling microscopy to study the effect as the “on” state appears higher than the “off” state by several Ångstroms.

Such switches are being used in the important field of molecular electronics.

Read the full details of this exciting work today:

Reversible light induced conductance switching of asymmetric diarylethenes on gold: surface and electronic studies
Arramel, Thomas C. Pijper, Tibor Kudernac, Nathalie Katsonis, Minko van der Maas, Ben L. Feringa and Bart J. van Wees
DOI: 10.1039/C3NR00832K