Nanoarrays Advance Biologic Detection

New nanoarrays of proteins with features more than 1,000 times smaller than those used in conventional arrays can yield more information more accurately in a shorter period of time. These nanoarrays have more than one million times the density of current commercial microarrays, say the developers.

The new detection technology, developed by researchers at Northwestern University (Evanston, IL, USA), was reported in the online February 7, 2002, issue of Science. The researchers invented a process called Dip-pen Nanolithography to make the nanoarrays, which allowed them to use an atomic force microscope tip as a nano-pen to write out a tiny protein array on a gold surface. With an array of protein dots as small as 100 nanometers in diameter, the gold surface in between the dots was processed to prevent it from absorbing target proteins and disturbing the readings. When an array on a chip was exposed to protein targets in solution, the protein on the substrate bound its complementary proteins. The atomic force microscope then read the chip and recorded a match where a change in height was detected.

Current technology uses arrays of either proteins or DNA on the micrometer level as screening tools for analyzing DNA, protein-protein interactions, cell biology, and drug testing. Miniaturizing these arrays should dramatically improve their capabilities. The researchers say the new arrays could lead to the next generation of proteomic arrays and new methods of diagnosing infectious diseases, including portable devices that could be used in a doctor's office to rapidly screen for diseases or in the field to detect biologic weapons.

"Creating patterns on a submicrometer level is important,” said Chad A. Mirkin, director of Northwestern's Institute for Nanotechnology and a professor of chemistry. "More detailed questions can be asked and answered when working on the nanometer scale. This is a fundamental advance in biorecognition.”