Molecular Robots Could Help Medications Target Specific Cells

Everyone has heard the expression, "the cure is worse than the disease," and there long has been truth to it, especially in the treatment of diseases like cancer that require strong medications that can harm healthy cells as well as they kill diseased ones.

But what if medications could specifically target only the areas inside the body that need repair? That is the promise of molecular nanorobots developed at Columbia University that can zero in on specific human cells and either provide medication or destroy them depending on the appropriate action, according to its inventors.

The work of a
team of scientists led by Milan Stojanovic, an associate professor of medicine and biomedical engineering at Columbia University Medical Center, the robots are not machines but a collection of DNA molecules, some of which are attached to antibodies.

Researchers designed them to seek specific cells and attach a fluorescent tag to the cell surfaces. Although other DNA nanorobots have been designed to deliver drugs to cells in a similar way, these new nanorobots are different in that they can distinguish cell populations that do not share a single distinctive feature, Stojanovic told Design News in an email. He and his fellow researchers also published their research in Nature Nanotechnology.

This characteristic is helpful especially in the treatment of cancer cells, which rarely have an exclusive feature that sets them apart, thus only making it possible to create drugs to target specific receptors in the cells that also target the same receptors in healthy cells. The nanorobots invented by Stojanovic and his team, however, can be more selective in their medication administration because they can target cells based on a collection of features, allowing them to avoid harming healthy cells when they target diseased cells. "Antibodies that otherwise may be used in therapy are used to bring components of cascades," Stojanovic told us. "The benefit would be highly specific tagging of cells for killing or for imaging. Side effects could potentially be eliminated."

To build the molecular robots, the team constructed three different components, each of which comprised a piece of double-stranded DNA attached to an antibody specific to one of the surface proteins. When the team added these components to a collection of cells, the robot's antibodies bound to their respective proteins and worked as a single unit.

The robot also has a fourth component that, when all three other components are attached to proteins, starts a chain reaction among the DNA strands that causes them to swap strands until the last antibody acquires a fluorescent-labeled DNA strand. This chain reaction lasts less than 15 minutes in a sample of human blood and ends with fluorescent markers only on the cells with the three surface proteins. "A cascade of reactions is enabled by proximity on cell surfaces," Stojanovic said. This process can be expanded to more than three surface proteins as well, he added.

Researchers will continue to work with these molecular robots, testing them next in mice. If animal tests are successful, it will be about a decade before the molecular robots would be available for use on actual patients, Stojanovic told us.

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