Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Improved characterization of nanoparticle clusters for EHS and biosensors research

27.10.2011
The tendency of nanoparticles to clump together in solution—"agglomeration"—is of great interest because the size of the clusters plays an important role in the behavior of the materials.

Toxicity, the persistence of the nanomaterials in the environment, their efficacy as biosensors and, for that matter, the accuracy of experiments to measure these factors, are all known to be affected by agglomeration and cluster size. Recent work* at the National Institute of Standards and Technology (NIST) offers a way to measure accurately both the distribution of cluster sizes in a sample and the characteristic light absorption for each size. The latter is important for the application of nanoparticles in biosensors.


Clusters of roughly 30-nanometer gold nanoparticles imaged by transmission electron microscopy. (Color added for clarity.)
Credit: Keene, FDA

A good example of the potential application of the work, says NIST biomedical engineer Justin Zook, is in the development of nanoparticle biosensors for ultrasensitive pregnancy tests. Gold nanoparticles can be coated with antibodies to a hormone** produced by an embryo shortly after conception. Multiple gold nanoparticles can bind to each hormone, forming clusters that have a different color from unclustered gold nanoparticles. But only certain size clusters are optimal for this measurement, so knowing how light absorbance changes with cluster size makes it easier to design the biosensors to result in just the right sized clusters.

The NIST team first prepared samples of gold nanoparticles—a nanomaterial widely used in biology—in a standard cell culture solution, using their previously developed technique for creating samples with a controlled distribution of sizes***. The particles are allowed to agglomerate in gradually growing clusters and the clumping process is "turned off" after varying lengths of time by adding a stabilizing agent that prevents further agglomeration.

They then used a technique called analytical ultracentrifugation (AUC) to simultaneously sort the clusters by size and measure their light absorption. The centrifuge causes the nanoparticle clusters to separate by size, the smaller, lighter clusters moving more slowly than the larger ones. While this is happening, the sample containers are repeatedly scanned with light and the amount of light passing through the sample for each color or frequency is recorded. The larger the cluster, the more light is absorbed by lower frequencies. Measuring the absorption by frequency across the sample containers allows the researchers both to watch the gradual separation of cluster sizes and to correlate absorbed frequencies with specific cluster sizes.

Most previous measurements of absorption spectra for solutions of nanoparticles were able only to measure the bulk spectra—the absorption of all the different cluster sizes mixed together. AUC makes it possible to measure the quantity and distribution of each nanoparticle cluster without being confounded by other components in complex biological mixtures, such as proteins. The technique previously had been used only to make these measurements for single nanoparticles in solution. The NIST researchers are the first to show that the procedure also works for nanoparticle clusters.

* J.M. Zook, V. Rastogi, R.I. MacCuspie, A.M. Keene and J. Fagan. Measuring agglomerate size distribution and dependence of localized surface plasmon resonance absorbance on gold nanoparticle agglomerate size using analytical ultracentrifugation. ACS Nano, Articles ASAP (As Soon As Publishable). Publication Date (Web): Sept. 3, 2011 DOI: 10.1021/nn202645b.
** HCG: Human chorionic gonadotropin.
*** See J.M. Zook, R.I. MacCuspie, L.E. Locascio, M.D. Halter and J.T. Elliott. Stable nanoparticle aggregates/agglomerates of different sizes and the effect of their size on hemolytic cytotoxicity. Nanotoxicology, published online Dec. 13, 2010 (DOI: 10.3109/17435390.2010.536615) and the Feb. 2, 2011, NIST Tech Beat article, "NIST Technique Controls Sizes of Nanoparticle Clusters for EHS Studies," at www.nist.gov/public_affairs/tech-beat/tb20110202.cfm#nanoparticles.

Michael E. Newman | EurekAlert!
Further information:
http://www.nist.gov

More articles from Life Sciences:

nachricht Cryo-electron microscopy achieves unprecedented resolution using new computational methods
24.03.2017 | DOE/Lawrence Berkeley National Laboratory

nachricht How cheetahs stay fit and healthy
24.03.2017 | Forschungsverbund Berlin e.V.

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Argon is not the 'dope' for metallic hydrogen

24.03.2017 | Materials Sciences

Astronomers find unexpected, dust-obscured star formation in distant galaxy

24.03.2017 | Physics and Astronomy

Gravitational wave kicks monster black hole out of galactic core

24.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>