Separating and distinguishing enantiomers poses a challenging task for chemical engineers, often causing them a considerable amount of frustration.
Enantiomers are molecules that possess nearly identical compositions but are mirror images of each other, much like a left and right hand. This property, known as chirality, is of great significance in chemistry. Despite their similar structures, left- and right-handed enantiomers often exhibit vastly different properties. In certain cases, a drug may have one enantiomer that induces undesirable side effects, such as headaches, while the other enantiomer provides relief.
According to Xiao Su, a researcher at the Beckman Institute for Advanced Science and Technology and an assistant professor of chemical and biomolecular engineering at the University of Illinois Urbana-Champaign, over half of the top 500 drugs used in the United States are enantiomeric. In light of this, Su, along with UIUC doctoral student Jemin Jeon and research scientist Johannes Elbert, has developed a novel system for electrochemically distinguishing between enantiomers.
This breakthrough holds tremendous implications for the drug manufacturing industry. As new drugs typically require a racemic mixture containing an equal proportion of left- and right-handed enantiomers, their system enables drug developers to more accurately determine the enantiomeric ratio within a given drug. Eventually, this advancement could lead to more efficient methods of separating enantiomers, ultimately enhancing drug efficacy.
Elbert explained, “When producing a drug, it is crucial to ascertain the quantity of each enantiomer present. It’s akin to a form of quality control.”
In their study published in Advanced Functional Materials, the team employed a versatile class of metal-containing polymers called “metallopolymers.” These polymers have previously been utilized for applications such as energy storage, water treatment, and selective separations. However, their use for enantiomer recognition has been limited due to the absence of chirality or handedness.
The researchers introduced a chiral center to the metallopolymers, enabling them to electrochemically detect two enantiomeric molecules, particularly those found in valuable pharmaceuticals.
Su elaborated, “The remarkable scientific advancement lies in demonstrating that these chiral redox polymers can serve as highly effective sensors, interacting specifically with their preferred enantiomers.”
The process of enantiomer recognition commences with the design of chemically engineered building blocks on the polymer, referred to as “redox centers.” These redox centers facilitate the polymer’s reduction and oxidation, hence the name “redox polymers,” through electron transfer. This mechanism allows the redox centers to selectively bind to and sense an enantiomer by detecting changes in current and potential.
Overall, this research represents a significant stride forward in the field of enantiomer recognition and holds promise for improving the efficiency and quality control of drug production.
“We have essentially generated a category of chiral metallopolymers that can serve as a versatile platform for future enantioselective studies,” remarked Su.
Moreover, the study unveils a fascinating phenomenon known as supramolecular chirality, wherein the polymer exhibits greater chirality than the individual redox-center building blocks themselves. The researchers harness this supramolecular chirality to enhance the sensing effect, representing a significant improvement over previous sensing techniques.
“With electrochemical methods, there is no requirement for external additives like chemical substances,” Su explained. “It is a sensing approach solely reliant on electrical input and readouts, providing flexibility and modularity.”
While various studies on chiral sensors have been conducted, many are limited to single-use applications. In contrast, the sensor developed by the Illinois researchers can be immobilized onto an interface, enabling reusability.
Although the newly developed sensor method is currently in the proof-of-concept stage, the researchers have already outlined their next steps.
“Now that we have demonstrated the sensing and recognition capabilities, the next phase involves translating these properties into separation techniques,” Su noted. “Currently, our system performs admirably in chiral sensing, but our aim is to create devices and even superior materials that can effectively purify enantiomers.”