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Researchers show how to catch and release tiny molecules

24 March 2015

Employing a novel microfluidic design, researchers have demonstrated a new way of detecting and extracting biomolecules from fluid mixtures.

A team of Harvard scientists has demonstrated a new way of detecting and extracting biomolecules from fluid mixtures (illustration courtesy of Peter Mallen, Harvard Medical School)

The approach, developed by researchers at Harvard's School of Engineering and Applied Sciences (SEAS), requires fewer steps, uses less energy, and achieves better performance than several techniques currently in use, and could lead to better technologies for medical diagnostics and chemical purification.

The biomolecule sorting technique was developed in the laboratory of Harvard SEAS' Professor Joanna Aizenberg, who is also a core faculty member at Harvard’s Wyss Institute for Biologically Inspired Engineering.

The new microfluidic device (described in a paper appearing in the journal, Nature Chemistry) is composed of microscopic 'fins' embedded in a hydrogel that is able to respond to different stimuli, such as temperature, pH, and light. Special DNA strands called aptamers that, under the right conditions, bind to a specific target molecule, are attached to the fins, which move the cargo between two chemically distinct environments. Modulating the pH levels of the solutions in those environments triggers the aptamers to 'catch' or 'release' the target biomolecule.

Following computer simulations Aizenberg’s team conducted proof-of-concept experiments in which they successfully separated thrombin, an enzyme in blood plasma that causes the clotting of blood, from several mixtures of proteins. Their research suggests that the technique could be applicable to other biomolecules, or used to determine chemical purity and other characteristics in inorganic and synthetic chemistry.

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

The capture and release of specific target biomolecules (image courtesy of Ankita Shastri and Ximin He)

The system is dynamic; its integrated components are highly tunable. For example, the chemistry of the hydrogel can be modified to respond to changes in temperature, light, electric and magnetic fields, and ionic concentration. Aptamers, meanwhile, can target a range of proteins and molecules in response to variations in pH levels, temperature, and salt.

Conventional biomolecule sorting systems rely on external electric fields, infrared radiation, and magnetic fields, and often require chemical modifications of the biomolecules of interest. That means set-ups can be used only once or require a series of sequential steps.

In contrast, the new catch-transport-and-release system is more efficient — requiring minimal steps and less energy, and achieving recovery of almost all of the target biomolecule through its continuous reusability.

The researchers say that the system could provide a means of removing contaminants from water or even be tailored to enable energy-efficient desalination of seawater and the extraction of valuable minerals from fluid mixtures.

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