Saturday, January 8, 2011

Physics Context: Chemists Use Nanotechnology to Penetrate Plant Cell Walls

A team from Iowa State University plant scientists and materials chemists have successfully used nanotechnology to penetrate plant cell walls and simultaneously provide the genes and chemicals that trigger the expression with controlled precision.  their breakthrough brings nanotechnology to plant biology and agricultural biotechnology, creating a powerful new tool for targeted delivery into plant cells.
This research, "Mesoporous Silica Nanoparticles Provide DNA and Chemicals into Plants," is a highlighted article in the May issue of Nature Nanotechnology.  Scientists are Kan Wang, professor of agronomy and director of the Center for Plant Transformation, Plant Sciences Institute, Victor Lin, professor of chemistry and senior scientist, U.S. Department of Energy's Ames Laboratory; Brian Trewyn, assistant scientist in chemistry, and Francois Torney, formerly a post-doctoral  Scientists at the Center for Plant Transformation and now a scientist with Biogemma, Clermond-Ferrand, France.

Currently, scientists managed to introduce genes into plant cells.  In a separate process, chemicals used to activate the function of genes.  This process is not precise and can be chemically toxic to plants.

"With the mesoporous nano-particles, we can give two biogenic species at the same time," said Wang.  "We can carry the gene and induces controlled at the same time and at the same location. It's never been done before."

Controlled release will improve the ability to study gene function in plants.  And in the future, scientists can use new technology to deliver imaging agents or chemicals inside cell walls.  This would provide plant biologists with a window into intracellular events.

Iowa Country teams, who has worked in research on plants less than three years, beginning with Iowa State University proprietary technology developed previously by Lin's research group.  It is porous silica nanoparticle system.  Round shape, the particles have arrays of independent porous channels.  Channels form a honeycomb-like structure that can be filled with chemicals or molecules.

"One gram of this type of material can have a total surface area of a football field, making it possible to carry large loads," said Trewyn.

Lin's nanoparticle has a unique "capping" strategy that seals the chemical goods inside.  In previous studies, his group successfully demonstrated that the chemical caps can be activated to pop open and release the cargo inside of animal cells.  A unique feature provides total control for delivery time

The first team to attempt to use the porous silica nanoparticle to deliver DNA through the rigid walls of plant cells does not work.  This technology has worked more easily in animal cells because they do not have walls.  Nanoparticles can enter animal cells through a process called endocytosis - the cell or swallow swallow molecules that are outside it.  Biologists try to mimic that process by removing plant cell wall (called the protoplast-making), forcing him to behave like an animal cell and swallow the particles.  It did not work.

They decided instead to modify the surface of the particle with a chemical coating.

"The team found a chemical we could use that makes nanoparticles look yummy to the plant cells so they would swallow the particles," Torney said.

It worked.  The nanoparticles were swallowed up by plant protoplast, which is a type of plant cells without cell walls round.

Most plant transformation, however, occur by using the gene gun, not through endocytosis.  To use the gene gun to introduce the nanoparticles to walled plant cells, chemists made another clever modification on the particle surface.  They synthesized even smaller gold particles to cap the nanoparticles.  This "golden gate" not only prevented chemical leakage, but also adds weight to the nanoparticles, enabling their delivery into plant cells by standard gene gun.

The biologists successfully used to introduce DNA technology and chemicals to, tobacco and maize plant Arabidopsis.

"The most remarkable advantage is that you can give a few things into plant cells at the same time and release them whenever you want," Torney said.

"Until now, you are at the mercy of nature when you deliver genes into cells," said Lin.  "There is no proper control, whether the cells will actually incorporate the gene and express the consequent protein. With this technology, we may be able to control the whole sequence in the future."

And once you get into the plant cell walls, will open a "new possibilities," said Wang.
"We really do not know what's going on inside cells. We are on the outside looking into this to make us inside where we can study the biology per se," Wang said.
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