Dr. Nie constructs the nanosensors, which he calls "smart nanoparticle probes," by attaching short pieces of DNA (oligonucleotides) to 2.5-nm gold nanocrystals, which serve both as scaffolds and as "quenchers" for fluorescence. The oligonucleotide molecules, which form into an arch-like shape, are labeled with a fluorescent dye at one end and a sulfur atom at the other end. When a nanoparticle probe binds to its target molecule, an energy transfer causes the quencher to be suppressed and the particle to illuminate. Dr. Nie believes the new nanoparticle probes will be more effective than conventional molecular beacons because their unique shape is better suited to binding with target molecules, and because their fluorescence changes very little with changes in temperature.
Dr. Nie hopes to use the nanoparticle beacons to trace specific proteins in cells for early cancer diagnosis and to monitor the effectiveness of drug therapy. He also plans to use the particles to quantify and identify gene sequences, proteins, infectious organisms, and genetic disorders. The particles might be able to profile a large number of genes and proteins simultaneously, allowing physicians to individualize cancer treatments based on the molecular differences in the cancers of various patients. Because of their novel structural and optical properties, these nanobeacons open new opportunities in biomolecular sensing and bioengineering.
"We expect that the integration of nanotechnology with biology and medicine will soon produce major advances in molecular diagnostics, therapeutics, molecular biology, and bioengineering," said Dr. Nie. "This new method of constructing nanobiosensors has potential as a unique tool for disease diagnosis and drug development."