Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Keeping cool by layering up

14.02.2014
Nanoparticles with a core–shell structure can minimize the overheating of cells during bioimaging experiments

Upconversion nanoparticles — new types of luminescent nanomaterials that release high-energy photons after laser light stimulation — can penetrate deeper into tissue and are more photochemically stable than conventional bioimaging agents, such as quantum dots and organic dyes.

Luminescent nanocrystals doped or impregnated with small amounts of rare-earth ytterbium (Yb) ions are particularly effective at photon upconversion. The specific lasers used to excite Yb dopants, however, can also heat water molecules in biological samples causing cell death or tissue damage.

Now, Xiaogang Liu from the A*STAR Institute of Materials Research and Engineering in Singapore and co-workers have synthesized a rare-earth-doped nanocrystal that can be excited at wavelengths within a safer ‘biological window’, thanks to a layered, core–shell design1.

Luminescent nanocrystals require ‘sensitizer’ components to absorb photons and transfer energy to activator sites, which emit the desired light radiation. Liu and co-workers investigated a different rare-earth dopant, neodymium (Nd), which absorbs the short-wavelength laser light that excites water molecules, thus avoiding overheating effects. Unfortunately, Nd can be doped into nanocrystals only at very low concentrations before cross-interactions with activators begin to extinguish the luminescence. This makes Nd-doped nanoparticles weak emitters compared to Yb-based biomarkers.

To resolve this problem, the researchers produced spherical nanoparticles containing layers with starkly different concentrations of Nd ions. They doped small amounts of Nd, Yb, and activator ions into nanocrystals of sodium yttrium fluoride (NaYF4), a material with a strong upconversion efficiency. They then synthesized a shell layer around the low-doped core containing a significantly higher Nd dopant concentration of 20 per cent. In this arrangement, the shell layer effectively harvests light and then transfers energy to the core, where low sensitizer concentrations minimize luminescence reduction.

The experiments revealed that the core–shell design dramatically improved the nanocrystals’ bioimaging capabilities — the new material had better light-harvesting capabilities than nanoparticles doped with pure Nd or Yb and achieved emission intensities seven times higher than pure NaYF4. Mechanistic studies showed that energy transfer between Nd and Yb ions in the nanoparticle core was key to overcoming the limitations of low dopant concentrations.

Next, the team tested their new materials by imaging an array of cervical cancer cells. While typical laser irradiation for Yb-doped biomarkers killed the cells within five minutes, the shorter wavelengths used for Nd-doped core–shell nanoparticles kept the cells viable over the same time.

“We plan to further improve the upconversion efficiency of our nanoparticles and use them for both bioimaging and drug delivery,” says Liu.

The A*STAR-affiliated researchers contributing to this research are from the Institute of Materials Research and Engineering

Journal information

Xie, X., Gao, N., Deng, R., Sun, Q., Xu, Q.-H. & Liu, X. Mechanistic investigation of photon upconversion in Nd3+-sensitized core–shell nanoparticles. Journal of the American Chemical Society 135, 12608–12611 (2013).

A*STAR Research | Research asia research news
Further information:
http://www.a-star.edu.sg
http://www.researchsea.com

More articles from Materials Sciences:

nachricht Transporting spin: A graphene and boron nitride heterostructure creates large spin signals
16.08.2017 | Graphene Flagship

nachricht From hot to cold: How to move objects at the nanoscale
10.08.2017 | Scuola Internazionale Superiore di Studi Avanzati

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

Im Focus: Scientists improve forecast of increasing hazard on Ecuadorian volcano

Researchers from the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science, the Italian Space Agency (ASI), and the Instituto Geofisico--Escuela Politecnica Nacional (IGEPN) of Ecuador, showed an increasing volcanic danger on Cotopaxi in Ecuador using a powerful technique known as Interferometric Synthetic Aperture Radar (InSAR).

The Andes region in which Cotopaxi volcano is located is known to contain some of the world's most serious volcanic hazard. A mid- to large-size eruption has...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

New thruster design increases efficiency for future spaceflight

16.08.2017 | Physics and Astronomy

Transporting spin: A graphene and boron nitride heterostructure creates large spin signals

16.08.2017 | Materials Sciences

A new method for the 3-D printing of living tissues

16.08.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>