Biochip Spots Single Viruses

Environmental sensors and handheld devices that quickly and easily detect and identify individual viruses would provide early warning of infections in individuals, the spread of disease in populations, and biological weapons attacks.

The rapid development of nanotechnology in recent years has given researchers tools for building highly sensitive virus detectors.

Harvard University researchers have built a detector from nanowires transistors that can identify individual virus particles in real time in unpurified samples. The researchers' prototype uses antibody proteins attached to the nanowires to briefly capture individual virus particles.

Labs-on-a-chip that are based on the device could be used to monitor diseases. The device could also be used to study how viruses bind to receptors and to detect individual biomolecules, including DNA and proteins, according to the researchers.

The researchers made their prototype by growing 20-nanometer-diameter silicon nanowires, mixing the nanowires with fluid, and flowing them into position across nickel contacts spaced two microns apart to form nanowire transistors. They coated the nanowires with aldehyde, then added antibody proteins, which adhered to the aldehyde. They configured a microfluidic channel to flow fluid containing the viruses across the nanowire sensors.

This prototype biochip contains nanowire transistors that can detect the presence of individual viruses. The tubes carry fluid samples to and from the chip. Source:  Lieber Group, Harvard University

When an individual virus binds to a nanowire transistor's antibody receptor, the transistor's electrical conductance changes, increasing or decreasing depending on whether the transistor carries positive or negative charge and the virus is positively or negatively charged.

The researchers demonstrated that they can detect simultaneous binding of two different types of viruses. The researchers' sensor arrays could be used practically in two to five years, according to the researchers.

The work appeared in the September 13, 2004 issue of the Proceedings of the National Acadamies of Science. Read the full story at www.trnmag.com.

-- TECHNOLOGY RESEARCH NEWS