Originally Published MDDI
June 2003
R&D DIGEST
Illuminating Nanoparticles Could Be Used for Imaging and Gene Detection |
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| Immunofluorescent images of human cancer cells labeled with green fluorescent dye. Applied to cancer markers, these quantum dots may enable doctors to isolate the disease at its earliest stages. |
Illuminating Nanoparticles Could Be Used for Imaging and Gene Detection
Nanoscale biosensors capable of detecting specific DNA sequences and genetic mutations in the lab could lead to new cancer detection methods or aid drug development. Such biosensors are now being developed by Shuming Nie, professor of biomedical engineering in the Coulter Department of Biomedical Engineering at Emory University (Atlanta) and Georgia Institute of Technology (Atlanta).
Previous research by Nie’s team has focused on using colored quantum dots to provide an early indication of cancer. The method involved embedding fluorescent, semiconducting quantum dots inside micro-sized beads. Biological macromolecules, such as antibodies, attached to the beads. By color-coding the quantum dots, they can then be used to label cancer markers for analysis, according to the researchers.
Nie calls the biosensors “smart nanoparticle probes.” He constructs them by attaching short pieces of DNA (oligonucleotides) to 2.5-nm gold nanocrystals. The crystals serve as scaffolds and as “quenchers” for fluorescence. The oligonucleotide molecules form an archlike shape and are labeled with a fluorescent dye at one end and a sulfur atom at the other. When a nanoparticle probe binds to its target molecule, an energy transfer suppresses the intended quencher and illuminates the particle.
According to Nie, the new nanoparticle probes are likely to be more effective than conventional molecular beacons because their unique shape is better suited to binding with target molecules. In addition, temperature variations cause only a slight change in the probes’ fluorescence.
Nie explains that the nanoparticle beacons could aid in providing an early cancer diagnosis and monitoring drug therapy effectiveness by tracing specific proteins in cells. In addition, he plans to use the particles to quantify and identify gene sequences, proteins, infectious organisms, and genetic disorders. He believes that the particles might be capable of profiling a large number of genes and proteins simultaneously. This would enable physicians to customize cancer treatments for individuals based on the molecular differences in each patient’s cancerous cells.
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