Christopher D. Salthouse, an electrical engineer at the University of Massachusetts Amherst, has been awarded a three-year, $351,303 grant from the National Science Foundation to develop integrated circuits that could lead to a new generation of biomedical sensors that are more sensitive, more portable and less costly than existing instruments. Salthouse says a goal of his research is to develop sophisticated integrated circuits that can be used in new devices that will replace the existing generation of fluorescence microscopes used by many biomedical and biological researchers.
"The basic idea is to re-engineer the microscope given that we don’t use our eyes," Salthouse says. "Since we are going to take a picture, we don’t need to sacrifice performance just to create an image you can see through an eyepiece."
He says the key to the process is finding out which of three different types of extremely small pixels - single points in a graphic image - can be engineered onto tiny computer chips to capture images in a nanosecond exposure. Salthouse says there are traditional pixels, photomixing pixels and single photon avalanche diodes that serve these functions and his research will determine which one, or combination of them, is most efficient for capturing the images. The different types of pixels register light from several sources in the biological samples being tested.
Scientists now routinely uses fluorescence in analyzing samples of cells, tissues or other biological materials. The fluorofores, fluorescent dyes used to mark specific cells, tissues or proteins, give off photons when exposed to light. Using traditional optical fluorescence microscopes, scientists insert the dyes into the samples and use lenses and various light filters to distinguish between different types of responses from the fluorofores when they are excited by light.
Salthouse says the circuitry he is designing will do away with the need for the lenses and filters. "We’ll replace the optical system with an integrated circuit that will capture the light from the fluorofores," Salthouse says. Such a technical advance could lead to a new generation of small, possibly hand-held sensors that could be used to test tissues or other biological samples in the field. Results from the tests could be sent wirelessly to computers where the samples can undergo analysis.
Salthouse is the Dev and Linda Gupta Assistant Professor in the UMass Amherst College of Engineering. He says the work on this grant combines two strands that have run through his academic career.
He earned his bachelor’s, master’s and doctoral degrees from the Massachusetts Institute of Technology. While earning his doctorate in circuit design in 2006, Salthouse developed micropower integrated circuits for cochlear implants, the biomedical devices that give hearing to the deaf.
Salthouse then moved to Massachusetts General Hospital in the Center for Systems Biology, where he worked on cell culture and mouse models of human disease and developed a variety of fluorescence imaging systems. He currently directs the Biomedical Electronics Laboratory at UMass Amherst.
He says his current research team is composed of engineers, many of whom have never worked on biomedical projects, and biologists, many of whom have never studied the engineering of circuit design.