by Holly Korschun

hemist and biomedical engineer Shuming Nie is designing tiny particles that could pack a big punch in cancer diagnosis and treatment.

Nie works in the field of nanotechnology, where scientists build new structures one atom or molecule at a time. In the nano world, particles consist of between 10 and 100 atoms each and are measured on a nanoscale of 1 to 100. One nanometer is one-billionth the size of a meter, and a typical 10-nanometer particle is 1,000 times smaller than the diameter of a human hair.

Until recently, nanotechnologists concentrated almost entirely on electronics, lasers, telecommunications, and materials manufacture. But in 1998, Nie predicted in a paper published in Science that the first practical applications of nanotechnology would be in biology and medicine.

"That turned out to be true," he says. "Now many nanotechnologists are working in medical and biology-related applications. Although electronics may be most likely to benefit from nanotechnology in the future, that's 10 to 20 years off, while biomedical applications are close to realization."

Nanoparticles assume special properties as they grow smaller. "If you break a piece of candy into two pieces, each piece is still sweet," explains Nie. "But if you continue to break it until you reach the nanometer scale, the smaller part will taste different and have different properties." Although nanoparticles are similar in size to biomolecules such as proteins and DNA, man-made nanoparticles can be engineered to have specific or multiple functions.

In this Lilliputian world of science, Nie and his former colleagues in Indiana constructed a kind of nanocrystal called a "quantum dot" -- a semiconductor particle that can conduct a small electric current.

By chemically binding quantum dots to particular genes and proteins, Nie now makes structures called bioconjugated quantum dots. These multipurpose particles can serve as fluorescent contrast agents in magnetic resonance imaging, as probes to trace specific proteins in cells for cancer diagnosis or to monitor the effectiveness of drug therapy, as tiny targeted smart bombs to deliver a controlled amount of drug to a particular type of cell, or as scaffolding material for tissue engineering.

The practical applications of nanoparticles are based on the different colors they absorb or emit in the light spectrum as their sizes change infinitesimally. A piece of gold, for instance, looks yellow; at nanoscale size, it's red. Even smaller, it could appear blue.

Using a ten-color spectrum, he can finely tune nanoparticles to carry out tracking tasks traditionally accomplished by organic dyes, which fade more quickly, can be toxic to cells, and cannot be used together because each dye requires a different light wavelength to be visible. Nanoparticles can be illuminated using just one laser beam. Because the dots' electrons are compact, they glow with bright, fluorescent colors, and scientists hope they will improve the sensitivity of diagnostic tests for molecules that are hard to detect.

Nie has embedded different-sized quantum dots into tiny beads made of a polymer material. This allows him to finely tune the beads in multiple color variations, then chemically bind the beads to biological molecules, such as proteins, DNA, or peptides. Theoretically, beads containing dots of tiny permutations of color could tag a million different proteins or DNA sequences. So far, Nie and his colleagues have used the nanobeads as targeted probes at the molecular, cellular, and tissue culture level, and are now moving into animal studies.

Along with Emory cancer urologist and fellow Georgia Cancer Coalition scientist Leland Chung, Nie is using nanoprobes to recognize particular genes and proteins in biopsy tissue from prostate cancer patients.

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Even when cells appear to be similar under the microscope, their genes and proteins may be decidedly different, which explains why cancer patients with comparable cancers sometimes respond differently to the same treatment. Using the nanoprobes, Nie hopes to measure hundreds or even thousands of different proteins within a tissue sample from one patient.

"We need multiple parameters to identify a particular variation of cancer," he points out. "If we're looking for a criminal, and know that the criminal weighs 150 pounds, many people fit that description. If we know that the criminal is 5 ft. 8 in. to 6 ft. tall, that narrows our search. If we add ten characteristics and an individual fits all, he or she is likely to be the right person. If we add 1,000 parameters and an individual fits all of them, we can be certain he or she is the criminal we are seeking."

Nie's group is now hard at work on drug delivery technology that will carry bioconjugated nanocrystals into specific tissues and cells to complete the individualized cancer therapy.

Holly Korschun is director of science communications for the Woodruff Health Sciences Center.