DNA origami suggests path to reusable, multifunctional biosensors

Utilizing an method known as DNA origami, scientists at Caltech have developed a method that would result in cheaper, reusable biomarker sensors for rapidly detecting proteins in bodily fluids, eliminating the necessity to ship samples out to lab facilities for testing.

“Our work offers a proof-of-concept displaying a path to a single-step technique that might be used to determine and measure nucleic acids and proteins,” says Paul Rothemund (BS ’94), a visiting affiliate at Caltech in computing and mathematical sciences, and computation and neural techniques.

A paper describing the work just lately appeared within the journal Proceedings of the Nationwide Academy of Sciences. The lead authors of the paper are former Caltech postdoctoral scholar Byoung-jin Jeon and present graduate scholar Matteo M. Guareschi, who accomplished the work in Rothemund’s lab.

In 2006, Rothemund printed the first paper on DNA origami, a method that gives easy but beautiful management over the design of molecular constructions on the nanoscale utilizing nothing greater than DNA.

Primarily, DNA origami allows lengthy strands of DNA to fold, by means of self-assembly, into any desired form. (Within the 2006 paper, Rothemund famously used the method to create miniature DNA smiley faces measuring 100 nanometers throughout and a couple of nanometers thick).

Researchers start with a protracted strand of DNA, the scaffold, in answer. As a result of the nucleotide bases that make up DNA bind in a identified means (adenine binds to thymine, and guanine binds to cytosine), the scientists can add a whole lot of brief sequences of complementary DNA understanding they may bind to the scaffold on both finish at identified places.

These brief, added items of DNA fold the scaffold and provides it form, appearing as “staples” that maintain the construction collectively. The method can then be used to create shapes starting from a map of North and South America to nanoscale transistors.

Within the new work, Rothemund and his colleagues used DNA origami to create a lilypad-like construction—a flat, round floor about 100 nanometers in diameter, tethered by a DNA linker to a gold electrode. Each the lilypad and the electrode have brief DNA strands out there to bind with an analyte, a molecule of curiosity in answer—whether or not that be a molecule of DNA, a protein, or an antibody.

When the analyte binds to these brief strands, the lilypad will get pulled right down to the gold floor, bringing 70 reporter molecules on the lilypad (which point out that the focused molecule is current) into contact with the gold floor. These reporters are redox reactive molecules, which means they will simply lose electrons throughout a response. So, once they get sufficiently near an electrode, an electrical present may be noticed. A stronger present signifies that extra of the molecule of curiosity is current.

Beforehand, the same method to creating biosensors was developed utilizing a single DNA strand somewhat than a DNA origami construction. That earlier work was led by Kevin W. Plaxco (Ph.D. ’94) of UC Santa Barbara, who can be an creator of the present paper.

Caltech’s Guareschi factors out that the brand new lilypad origami is giant in comparison with a single DNA strand. “Which means it could possibly match 70 reporters on a single molecule and maintain them away from the floor earlier than binding. Then when the analyte is certain and the lilypad reaches the electrode, there’s a giant sign acquire, making the change simple to detect,” Guareschi says.

The comparatively giant dimension of the lilypad origami additionally implies that the system can readily accommodate and detect bigger molecules, reminiscent of giant proteins. Within the new paper, the group confirmed that the 2 brief DNA strands on the lilypad and the gold floor might be used as adapters, making it a sensor for proteins somewhat than for DNA.

Within the work, the researchers added the vitamin biotin to these brief DNA strands to show the system right into a sensor for the protein streptavidin. Then they added a DNA aptamer, a DNA strand that may bind to a selected protein; on this case, they used an aptamer that binds to a protein known as platelet-derived progress issue BB (PDGF-BB), which might be used to assist diagnose ailments reminiscent of cirrhosis and inflammatory bowel illness.

“We simply add these easy molecules to the system, and it is able to sense one thing completely different,” Guareschi says. “It is giant sufficient to accommodate no matter you throw at it—that might be aptamers, nanobodies, fragments of antibodies—and it would not should be fully redesigned each time.”

The researchers additionally present that the sensor may be reused a number of instances, with new adapters added every spherical for various detections. Though the efficiency barely degrades over time, the present system might be reused not less than 4 instances.

Sooner or later, the group hopes the system may additionally be helpful for proteomics—research that decide what proteins are in a pattern and at what concentrations. “You might have a number of sensors on the similar time with completely different analytes, after which you can do a wash, change the analytes, and remeasure. And you can do this a number of instances,” Guareschi says. “Inside a number of hours, you can measure a whole lot of proteins utilizing a single system.”

Extra authors of the paper, “Modular DNA origami-based electrochemical detection of DNA and proteins,” are Jaimie M. Stewart of UCLA; Emily Wu and Ashwin Gopinath of MIT, Netzahualcóyotl Arroyo-Currás of Johns Hopkins College Faculty of Drugs, Philippe Dauphin-Ducharme of the Université de Sherbrooke in Canada; and Philip S. Lukeman of St. John’s College in New York.