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New and Better Nanoparticles for Probes of Embryos Reported by Xu Research Group

The research group of Old Dominion University chemist and biochemist X. Nancy Xu has reported in the American Chemical Society journal, ACS Nano, its discovery of new ways to synthesize silver nanoparticles that are particularly well suited for complex probes of live zebra fish embryos.

New monodisperse-or size-consistent-nanoparticles that the researchers create using a simple washing step are stable (non aggregated) in solution for months, they write in the article published in June.

"Others can use the same approach to prepare other types of purified nanoparticles in solution," said Xu. The researchers' findings solve a major obstacle, stability of nanoparticles in solution, for achieving a wide variety of applications of nanoparticle probes, such as an in vivo imaging. They deploy these tiny probes to simultaneously image multiple nanoenvironments of in vivo biological systems, such as zebra fish embryos, in real time.

The article, "Design of Stable and Uniform Single Nanoparticle Photonics for In Vivo Dynamics Imaging of Nanoenvironments of Zebra Fish Embryonic Fluids," was written by Prakash D. Nallathamby and Kerry J. Lee, doctoral students in the Xu group, as well as Xu.

Using improved nanoparticles, developed by means of the simple washing step that promotes uniform particle size, the researchers say they have devised a way to prepare purified, stable and optically monodisperse silver nanoparticles, which is needed to map the embryonic fluid dynamics that are so important in the development of embryos.

At the outset of embryo growth, embryonic stem cells divide and differentiate into the various cell lineages that become different parts of the organism. "One of the determining factors of cell differentiation into different lineages is the nanoenvironments surrounding the cells," the researchers explain in the article. "Viscosity and flow patterns surrounding the cells in the embryonic fluids affect directions of movement of signaling molecules and migration of cells, which control embryonic morphogenesis, underscoring the importance of probing the viscosity gradients and flow patterns of embryonic fluid in vivo at nanometer resolution in real time."

Unlike the researchers in previous studies, the Xu team could use identically sized nanoparticles to simultaneously investigate several dynamic events of interest in vivo in real time, according to the article.

Zebra fish and humans have genetic and other similarities that make the fish particularly useful in research concerning human physiology and diseases. The fish embryos are also transparent and develop outside of their mothers, which offered the researchers a better opportunity to directly image embryonic fluid dynamics and the early development of embryos simultaneously. This offers "the possibility of better understanding the role of the embryonic fluid dynamics in the early development of embryos," the researchers write.

In 2007, the Xu group reported the results of a study of the entry of nanoparticles into zebra fish embryos and of dose-dependent toxicity of silver nanoparticles on embryonic development. One aim of Xu's research is the development of an in vivo system to screen the biocompatibility and toxicity of nanomaterials.

Single-nanoparticle photonics and the single nanoparticle imaging system developed by the Xu group enable the direct characterization of size and location of nanoparticles inside cells and embryos.

Beginning about eight years ago, Xu, an associate professor of chemistry and biochemistry, reported research findings that placed her in the vanguard of scientists using very tiny nanoparticle optical sensors to study living cells. These studies and innovations helped Xu and her group to win a 2007 Nanotech Brief Nano 50th award from NASA. She currently has grants totaling more than $2.5 million from the National Science Foundation and the National Institutes of Health to support her work.

Xu was named in a 2006 article prepared by the National Cancer Institute as a pioneering developer of nanotechnology that can be used in the war against cancer. The article, titled "Mission to the Inside of a Living Cell," noted the benefits of studying biochemical reactions inside live cells, rather than dead cells. Similar studies in the past were conducted with dead cells or purified biomolecules extracted from cells. The article also gave the Xu group high marks for producing silver nanoparticles that are exceedingly bright and do not photodecompose.

This article was posted on: July 3, 2008

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