A sensor constructed of a stacked array of antibodies could help detect diseases such as malaria or tuberculosis.

In the research by MIT chemical engineers, molecular self-assembly was used to build sensors containing a large number of stacked layers of antibodies. The method produces 100 times more sensitivity than existing antibody-based sensors.

Molecules arrange themselves in a structure that minimizes the interactions between protein and polymer segments. Molecules arrange themselves in a structure that minimizes the interactions between protein and polymer segments. The current technique for creating large arrays of antibodies by chemically or physically bonding them to the surface produces a single layer. However, the more antibody molecules there are on the surface, the lower the concentration of molecules they can detect. By stacking the layers of antibodies on top of each other the sensor sensitivity can be improved, the researchers say.

"You can have a big impact on biosensors by potentially improving the sensitivity by several orders of magnitude," says associate professor of chemical engineering Bradley Olsen.

The researchers found that they could use self-assembly to force antibodies and other proteins to form layers by attaching each protein to a polymer tail. Since the protein and polymer are bonded together they can separate from each other by a distance about the size of one molecule.

"If you do this in three dimensions, then you get things like cylinders of protein surrounded by polymer, or alternating layers of protein and polymer," says Olsen. When the researchers attached each protein to a polymer chain known as a PNIPAM, they were able to coat a solution of these molecules onto a surface forming a film containing between 10 and 100 layers of the protein-polymer structures.

Another potentially useful feature of these arrays is that they contain nanoscale channels that allow a sample to flow through the entire sensor. Olsen’s latest project is to create sensors with antibodies specialized to detect pathogens from blood or urine samples.

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