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DIAMOND FILMS FOR BIOSENSING New method yields stable films useful for detecting biomolecules MITCH JACOBY PHOTO BY MITCH JACOBY Real-time sensing and long-term monitoring of biological molecules may have just taken a key step forward, thanks to an advance in surface chemistry. Researchers have devised a procedure for preparing DNA-modified diamond films that may form the basis of stable and selective detectors. Future designs of sophisticated biological sensors are sure to take advantage of signal amplification, processing, relaying, and other strengths of microelectronics. For that reason, scientists have developed procedures for attaching biologically active molecules to microelectronics-compatible materials such as gold, silicon, and glass. But the interfaces between those materials and biomolecules have lacked long-term stability, which is critical to developing integrated biological sensors. Now, a team of researchers at the University of Wisconsin, Madison, including chemistry professor Robert J. Hamers and graduate student Wensha Yang; Argonne National Laboratory; and the Naval Research Laboratory, Washington, D.C., has demonstrated a new chemical method for preparing highly stable DNA-modified thin films of nanocrystalline diamond—a material that is inherently compatible with microelectronics processing. The group reports that in studies conducted with fluorescently tagged molecules, diamond test samples withstood 30 cycles of DNA hybridization and denaturization reactions without any measurable decrease in signal intensity and without loss of selectivity. In comparison tests conducted by the group on gold, silicon, glass, and glassy carbon specimens prepared via the same methods, nothing outperformed diamond [Nat. Mater., published online Nov. 24, http://dx.doi.org/10.1038/nmat779]. Hamers explains that, in the new procedure, a long-chain molecule with alkene and amine functional groups is bonded to the diamond films via a UV photoattachment process. The amine group is reacted with a sulfosuccinimidyl carboxylate and then treated with thiol-modified DNA to produce the DNA-capped diamond films. The present study is based on fluorescence measurements, But that in recent unpublished work, Hamers and coworkers have detected DNA hybridization reactions directly by measuring electronic signatures of binding events. The idea of a “bio cell phone” is not that far-fetched, Hamers asserts. He envisions a small, integrated device for continuous sensing of hazardous biological agents, for example, that can be used for monitoring airports and other public areas. When a target molecule is detected, the device could trigger an alarm, relay a signal, and broadcast a communication, he says |
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