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Engineers Build Compact Diagnostic Biosensor

DNA strand (NSF)

(James. J. Caras, National Science Foundation)

Engineers at Vanderbilt University in Nashville, Tennessee have developed a small silicon-based sensor for medical diagnostics and detecting toxins. Their findings appear in current issue of the journal Optics Express.

The sensor was originally designed to detect particular DNA sequences, which can be helpful in identifying if a person is predisposed to disorders or conditions such as heart disease or certain kinds of cancer. These same kinds of biochemical sensors can detect dangerous substances in the environment or specific molecules in the blood that could signal life-threatening diseases.

Current sensor technologies, however, run into problems when testing  some substances. The large size of most biosensors make it difficult to evaluate the minute sizes of some of the chemicals to be detected. In many cases, when attempting to sense something very small with a large sensor, the small molecules don’t register on sensor’s radar.

Vanderbilt engineering grad student Xing Wei and professor Sharon Weiss developed a biosensor that addresses this problem with features that are comparative in size to the molecules being detected, thus increasing the sensitivity of the technology. They used a porous silicon material, which acts as a small sponge filled with targeted substances that change its properties. This “seeded” sponge-like sensor then becomes a detector for those targeted substances — e.g., a particular strand of DNA — that’s more sensitive to small molecules.

The sponge-like silicon material provides a vastly larger total surface area to attach the targeted molecules, as much 10,000 times more test surface area with the same footprint. In addition, the external surface texture of the sensor has a lattice quality that allows for light to interact with the sensor. The interaction of light with the sensor then returns light at various angles or colors.

These optical interactions, say the researchers, can provide valuable diagnostics. “When we infiltrate the molecules that we want to detect and they stay in the sensor and attach, they change the optical density of the porous silicon and, consequently, the angle or the color of light that comes back out,” says Weiss.

“By knowing how much the angle changes, for example, we can quantify how many molecules are present. So not only can we identify our DNA sequence or toxin, Weiss adds, “we can also know how much is present as well. For diagnostics, it’s very helpful to know how much is present.”

Read more: Engineers Develop Biomarker Breathalyzer Diagnostics

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