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March 24, 2015

Biomolecules Sorted with Catch-and-Release System

Capture and release of target biomolecules occurs by the concerted, dynamic, and reversible action of hydrogel volume change and aptamer binding through changes in solution pH. [Peter Mallen, Harvard Medical School]

  • A microtubule-inspired microfluidic system that resembles a microscopic forest of arms can pluck biomolecules out of liquid mixtures, carry them from one chemical stream to another, and then release them. The system, which is dynamic and tunable, may be suitable for applications in clinical diagnostics, target characterization, environmental analysis, and chemical purification.

    Each “arm” inside the microfluidic system can bend because it is embedded in a hydrogel that shrinks or expands, as needed, in response to various stimuli, such as changes in temperature, pH, and light. And each arm is topped with a “hand” that is made of a DNA aptamer. The hand can be made to open and close—again, as needed—grabbing and releasing specific kinds of molecules in response to changes in temperature, pH, and ionic concentration. When the hand clutches a biomolecule, it is in one chemical stream; when it releases the molecule, it is in another. The two streams are parallel, laminar flows.

    The system was developed by scientists at Harvard, Arizona State University, and the University of Pittsburgh. It was described March 23 in Nature Chemistry, in an article entitled, “An aptamer-functionalized chemomechanically modulated biomolecule catch-and-release system.” The authors of the Nature Chemistry study assert that their system requires fewer steps, uses less energy, and achieves better performance than several techniques currently in use.

    “To demonstrate the utility of the system, we focus on the effective separation of thrombin by synchronizing the pH-dependent binding strength of a thrombin-specific aptamer with volume changes of the pH-responsive hydrogel in a biphasic microfluidic regime,” wrote the authors. “[We] show a nondestructive separation that has a quantitative sorting efficiency, as well as the system's stability and amenability to multiple solution recycling.”

    According to a release issued by Harvard, the new catch-and-release system is an improvement over conventional biomolecule sorting systems, which rely on external electric fields, infrared radiation, and magnetic fields, and often require chemical modifications of the biomolecules of interest. These conventional systems, the release asserted, can be used only once or require a series of sequential steps. The catch-and-release system, in contrast, can recover almost all of the target biomolecule through its continuous reusability.

    The development effort was led by Joanna Aizenberg, who is affiliated with the Harvard School of Engineering and Applied Sciences, the Kavli Institute for Bionano Science and Technology, and the Wyss Institute for Biologically Inspired Engineering.

    “Our adaptive hybrid sorting system presents an efficient chemomechanical transductor, capable of highly selective separation of a target species from a complex mixture—all without destructive chemical modifications and high-energy inputs,” Dr. Aizenberg said. “This new approach holds promise for the next-generation, energy-efficient separation and purification technologies and medical diagnostics.”

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