Jonathan Parquette is involved in the study of a new kind of artificial protein-like molecule created at Ohio State that could one day lead to new drugs and new medical treatments.     By Kevin Fitzsimons

Protein-like molecules could form electronics, medical devices

A new kind of artificial protein-like molecule created at Ohio State could one day lead to new drugs, new medical treatments -- and even faster computer chips.

"Proteins come in so many shapes and sizes that they are able to perform a wide variety of functions," said Jonathan Parquette, assistant professor of chemistry. "We wanted to mimic that versatile structure in a synthetic form."

Parquette and his students built the molecules, called dendrimers, from tiny, spaghetti-like plastic filaments. Researchers have long tried to mimic the shape of proteins using dendrimers, but the Ohio State group is the first to coax the soft, tangled filaments to maintain a shape that suits needed applications.

The molecule is shaped like a sphere, supported by branching beams of polymer inside, with hollow portions that could theoretically hold drugs or other chemicals.

Parquette described his work Sept. 23 at the BioMEMS and Biomedical Nanotechnology World 2001 meeting in Columbus. The conference was co-hosted by the University and led by Mauro Ferrari, director of the Biomedical Engineering Center and associate director of the Davis Heart and Lung Institute.

BioMEMS, or biomedical microelectromechanical systems, are microscopic medical devices under development around the world. The tiny devices can be as small as a few millionths of a meter -- much smaller than the width of a human hair.

Parquette's synthetic protein molecule belongs to the realm of nanotechnology, which concerns devices even smaller than bioMEMS. The molecule is about the same size as a small protein or a short sequence of DNA -- a few tens of atoms across.

The chemists are working toward developing the molecule into a larger, more complex structure.

Ultimately, synthetic proteins could act as devices to deliver medicine to tumors or other sites of disease in the body. They could also act as catalysts for chemical reactions that produce drugs, or form computer chips for light-responsive molecular electronics.

For these molecules to perform such tasks, the outer shell would have to open and close on cue, Parquette explained. A molecule could locate a tumor, for instance, and unravel its structure to release cancer-fighting medicine from within.

"Along the outside of the molecule, the atoms fasten together like a zipper," Parquette explained.

"Getting them to zip up is half the puzzle. Getting them to unzip on demand is the other half."

With chemicals, the researchers caused the normally long, stringy dendrimers to fold into a protein-like shape. Then they added other chemicals that bound themselves to select sites along the dendrimers, effectively zipping together layers of folds and stiffening the structure overall.

Currently, Parquette and his colleagues are investigating whether light could be used as a stimulus to make the dendrimers unfold. If so, the protein-like molecules could form the basis for extremely tiny, very fast computer chips.

Whereas semiconductor computer chips carry a digital signal of "one" or "zero" based on the presence of an electron, molecular computer chips stimulated by light from fiber optics could carry a signal based on whether individual molecules were "zipped" or "unzipped."

For Parquette, this work has helped to explain how nature builds its own micrometer- and nanometer-size structures.

"On the nanoscale, it seems that atoms have a way of cooperating together to assume certain structures for specific functions. If we can learn to harness that cooperativity, we may be able to form better synthetic molecules," Parquette said.

"As soon as you think you're pretty smart about something, it turns out nature has thought of it first," he said with a smile.

This work was supported by Parquette's Faculty Early Career Development award from the National Science Foundation.

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Better way found to glue tiny parts for medical devices

Engineers at Ohio State have mastered a critical step for manufacturing tiny medical devices. This new technique for sealing plastic casings could bring medical nanotechnology closer to reality.

Led by L. James Lee, professor of chemical engineering, the researchers found that their technique aids the flow of medicine and other fluids through such devices, and can even alter the material on the surface of a device to suit different medical applications.

"Plastics have great potential for use in these devices, because they are inexpensive and easy to shape into individual parts, but sealing a tiny casing poses a special challenge," Lee said. "So does altering the characteristics of the plastic to suit different medical tasks. Our method allows someone to do both in one shot."

Lee and his colleagues described the method, called "resin-gas injection assisted bonding," on Sept. 23 at the BioMEMS and Biomedical Nanotechnology World 2001 conference. BioMEMS, or biomedical microelectromechanical systems, are microscopic medical devices under development around the world. Nanotechnology concerns devices even smaller than bioMEMS.

One day these devices could deliver medicine directly to tumors or other sites of disease in the body.

www.osu.edu/researchnews/archive/nanoglue.htm