Professors at Colorado State Univ. report that they can detect proteins landing on a silicon chip by directing a laser or LED beam along the surface of the chip and watching where the light is deflected very slightly toward the proteins. Surface treatments that allow only specific types of proteins or other biomolecules to stick to particular areas on the chip let the researchers test what proteins are present in a fluid such as blood, urine or saliva.
The new chip is intended to simplify and speed up medical diagnostics and other biosensor applications by eliminating extra chemicals, special equipment and complex steps often required for current laboratory tests. The ability to sense the type of biomolecules reaching the chip qualifies it as a biosensor - a class of devices used in medical, environmental and food safety applications."Our team is working to reverse the current trends of escalating prices for medical tests by applying chips that are made the same way as integrated circuits, which allow greater performance in computers at lower costs," said Kevin Lear, a computer engineering professor leading the research. He noted that using silicon microelectronics technology makes it easy to include "smarts" on the chip to interpret the sensor signals and send them to a laptop or cell phone.
Lear's co-principal investigator is David Dandy, head of the Chemical and Biological Engineering department.
How the CSU technology works: An optical waveguide - similar to a fiber optic - is molded on the top surface of a microchip. Light flowing along the waveguide is deflected toward molecules captured on the surface of the chip. Using small patterned patches of special molecules such as antibodies or DNA that only latch onto matching molecules on the chip allows scientists to simultaneously detect the presence of many types of tiny molecules.
The chip can distinguish different proteins by using optical detectors, equivalent to microscopic solar cells, to determine where the light is pulled toward the surface. Their research may speed the detection of biological substances in body fluids such as blood that can more quickly provide information about the state of a patient's health.
The scientists say the technology will be more compact, self-contained and self-interpreting than conventional diagnostics - important traits particularly in the developing world where basic medical care resources are scarce. They added the method could be commercialized cheaply because the chips can be manufactured with older, less expensive semiconductor technology.
The approach can measure a wide range of protein molecule sizes, which are much too small to be seen even with a microscope, from 100-nm viruses - a relative giant in the biomolecular world at a 1,000 times smaller than the diameter of a hair - down to 1 nm. The professors believe the technique will ultimately sense a layer the thickness of a single atom covering only a tiny surface area.
For now, the scientists have focused their research on diagnosing tuberculosis. Colorado State has world-renowned tuberculosis researchers such as Richard Slayden, associate professor of Microbiology, Immunology and Pathology at CSU, who is working on novel treatments, vaccines and diagnostics, particularly for extreme drug-resistant strains.
Source: Colorado State Univ.