Early detection of viruses from patient specimens holds the best potential for reducing the spread of infection when a cure does not exist or may not be readily available in population-sized quantities. This need may be even more critical when working in the field. Individuals with no outward manifestation of symptoms could be quickly and accurately quarantined to minimize the possibility of an epidemic, when an outbreak of a particularly contagious and virulent strain of influenza or similar disease occurs.
Now researchers from the University of Twente, Paradocs Group, bioMérieux, and LioniX in the Netherlands have developed a device for fast pathogen detection. It uses a laser coupled to a waveguide composed of four parallel optical channels, each coated with antibodies specific to a certain protein or virus [Ymeti et al., Nano Lett. (2007) doi: 10.1021/nl062595n].
The team demonstrate the detection of herpes simplex virus type 1 (HSV-1) by coating one of the waveguide channels with the appropriate herpes antibodies. They are able to detect the virus over a range of concentrations ranging from 103/ml (very low) to 107/ml (very high).
By combining the light exiting from this channel with that from a reference channel an interference pattern can be generated. Virus binding to the antibody-coated waveguide is probed by the evanescent field of the guided light modes, causing a phase change and a change in the interference pattern.
The apparatus is general enough that any antibody can be used to coat a channel for detection. “The sensor can be extended to any virus that has specific antibodies available, such as human immunodeficiency virus (HIV), severe acute respiratory syndrome (SARS) coronavirus, hepatitis B and C, or H5N1 bird ‘flu virus,” explains lead author Aurel Ymeti from the University of Twente.
He adds that, in its current configuration, the multichannel character of the sensor allows up to three different viruses or other pathogens to be detected simultaneously. Redesign of the waveguides with more channels could allow multiplexed detection of even more pathogens.
Ymeti's ultimate goal is a point-of-care device that can be used quickly and easily in the field to detect viruses from either human or animal body fluid samples. He envisions a portable readout unit and disposable chip, and is optimistic that the engineering challenges can be met.
“So far we have demonstrated the sensitivity of the device in a laboratory setting, including in complex solutions containing serum proteins,” he says. “The key issues that remain to be addressed are the design and development of a practical prototype and clinical tests on real clinical samples. Depending on our efforts, the first commercial prototype could be available to the medical community in the next two to three years.”