SENSORS, ARRAYS, MICROFLUIDICS
STU BORMAN, C&EN WASHINGTON
Chad A. Mirkin and coworkers at Northwestern developed a new type of DNA detection technique that is 10 times more sensitive and 100,000 times more selective than previous oligonucleotide detection methods [Science, 295, 1503 (2002); C&EN, Feb. 25, page 8]. Selective binding of DNA-derivatized gold nanoparticles to target DNA strands causes the nanoparticles to line up between electrodes, generating an electrical signal. The technique could lead to a handheld device for point-of-care biodetection.
Mirkin's group developed another technique in which gold nanoparticle probes labeled with oligonucleotides and Raman-active dyes are used for DNA and RNA detection [Science, 297, 1536 (2002); C&EN, Sept. 2, page 13]. The surface-enhanced Raman scattering technique--which has femtomolar detection limits and can detect multiple pathogens simultaneously in one solution--is a potential alternative to molecular fluorescence-based biodetection.
A method for detecting specific DNA sequences at picomolar levels was developed by Guillermo C. Bazan, Alan J. Heeger, and coworkers at UC Santa Barbara [Proc. Natl. Acad. Sci. USA, 99, 10954 (2002); C&EN, Aug. 12, page 8]. In the technique, a chromophore lights up only when a peptide nucleic acid encounters and binds to a complementary single-stranded DNA analyte.
Sensitive and inexpensive nanoscale optical biosensors for monitoring receptor binding, adsorption, and other analyte-surface interactions were developed by Richard P. Van Duyne and Amanda J. Haes of Northwestern University [J. Am. Chem. Soc., 124, 10596 (2002); C&EN, Aug. 19, page 10; Anal. Chem., 74, 559A (2002)]. The surface plasmon resonance-based biosensors are capable of detecting 10 to 100 molecules per nanoparticle.
Robert J. Hamers of the University of Wisconsin, Madison, and coworkers developed a new method for preparing highly stable DNA-modified thin films of nanocrystalline diamond that could be useful in biosensing [Nat. Mater., 1, 253 (2002); C&EN, Dec. 2, page 14].
Membrane microarrays created by Joydeep Lahiri and coworkers at Corning combine the convenience, multiplexing, and miniaturization of microarrays with the ability to study membrane-bound molecules in near-native environments [J. Am. Chem. Soc., 124, 2394 (2002); C&EN, March 18, page 7]. Potential applications include drug screening and toxin detection.
It's hard to mix solutions efficiently in microfluidic channels, where flow tends to be laminar and nonturbulent. But a team led by Abraham D. Stroock and George M. Whitesides at Harvard devised a way to do it: by embedding ridges in channel walls [Science, 295, 647 (2002); C&EN, Jan. 28, page 52].
And the microfluidic equivalent of an integrated circuit--with thousands of valves and hundreds of individually addressable chambers on a 1-by-1-inch chip--was made by Stephen R. Quake and coworkers at Caltech [Science, 298, 580 (2002); C&EN, Sept. 30, page 11]. Potential applications include structural genomics, genetic analysis, and high-throughput screening.