Host-Guest Liquid Gating Mechanism with Specific Recognition Interface Behavior for Universal Quantitative Chemical Detection

Chemical detection offers vital means for in-depth understanding and guiding life and production. Here, we put forward a host-guest liquid gating mechanism to translate molecular interface recognition behavior into visually quantifiable detection signals without optical/electrical equipment.

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Quantitative detection methods used for identification, quantification, property evaluation of biochemical molecules provide key guidance in the fields of environmental assessment, homeland security, clinical drug testing and health care systems, especially during the current epidemic period, developing new technologies to achieve portable and rapid target molecules. The principles of current analytical methods rely mainly on molecular recognition events, to convert information about the analytes into electrically detectable spectroscopic signals1. If analytical signal transduction method that do not require expensive optical detectors or electrochemical components are available, it will facilitate t the development of sensors for applications in resource-limited environments such as fieldwork or underdeveloped areas.

In our recent paper published in Nature Communications, we put forward a host-guest liquid gating mechanism to translate biochemical molecular interface recognition behaviors into visually quantifiable detection signals without optical/electrical equipment to open avenues for analytical chemistry, biochemistry, biomedical engineering and beyond (Fig. 1). The idea of using liquids as a structural material to build responsive gates has attracted increasing attention because it provides a special combination of dynamic and interface physicochemical behaviors2, and it has been selected as one of the 2020 Top Ten Emerging Technologies by the International Union of Pure and Applied Chemistry (IUPAC)3, 4. The behavior of a liquid gating technology is based on reversible reconfigurable gates, which can use a capillary-driven functional gating liquid to seal microscale pores that can be opened at a certain pressure5, 6. The liquid gating technology is emerging as a promising approach to address these needs as an easily deployable detection platform because of its very sensitive response to target stimuli such as chemical, physical or biological targets7, 8. In this host-guest liquid gating system, surfactant molecules in solution usually reside preferentially at the interface with the interfacial structure of the hydrophobic end facing the air phase, allowing surface activity to reduce the system's surface tension. The surface activity is shielded when the hydrophobic chain of the surfactant molecule enters the hydrophobic cavity of a macrocyclic molecule, which provides a potential framework for the analyst-response mechanism. When a specific and competitive target molecule is present in the gating liquid, the surfactant indicator is displaced into the solution, where it occupies the surface, leading to a low PCritical and the system releases gas. The concentration of target molecule can be visually quantified by reading the movement distance of the marker or observing the color change of indicator solution. In contrast, nonspecific molecules (weak competitors) cannot displace the surfactant indicator, and the system still maintains a high PCritical.

Fig. 1. Host-guest liquid gating system (HG-LGS). a Schematic of the HG-LGS for quantitative visual chemical detection. The gating liquid consists of a host-guest system with a macrocyclic-surfactant. Macrocyclic molecules modulate the gas-liquid interface property of the gating liquid by shielding the surfactant to form an inclusion complex, in which the hydrophobic part of the surfactant is inserted into the macrocyclic cavity. When the specific target molecules are in the gating liquid, the HG-LGS releases gas with the formation of the macrocyclic-target complex, pushing the marker forward in the thin tube. The higher the concentration of the target molecule, the farther the marker moves. The concentration of target molecule can be visually quantified by reading the movement distance of the marker or observing the color change of indicator solution. The system does not respond to nonspecific molecules. b Relationships among the movement distance of the marker, the transmembrane critical pressure (PCritical) of the gas in the HG-LGS, and the concentration of the target molecule (CAnalyts) in various macrocyclic: surfactant ratios (NHost:Surfactant).

In summary, we have demonstrated a specific recognition interface behavior mechanism that converts molecular interface recognition behavior to visually quantifiable detection signals. This work will be a milestone for liquid gating technology, because it is the first time to realize chemical quantitative detection instead of qualitative detection (such as dipole-induced reconfiguration)8 by this technology , which will open avenues for more in-depth exploration of chemical detection and spur advances in environmental monitoring, point-of-care test, public health security, and biomedical applications.

To read more about our work at Nature Communications:

For more information of the Xu Hou research group, please visit:


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  3. Yu S, Pan L, Zhang Y, Chen X & Hou X. Liquid gating technology. Pure and Applied Chemistry 93, 1353-1370 (2021).
  4. Gomollón-Bel F. Ten chemical innovations that will change our world. Chemistry International 42, 3-9 (2020).
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Xu Hou

Professor, Xiamen University

Xu Hou did his postdoctoral research in Prof. Joanna Aizenberg’s group at Harvard University, USA (2012–2015). Later he did the collaboration research as a visiting scientist in Prof. Ali Khademhosseini lab at Harvard Medical School. He joined in Xiamen University in 2016, and now he is a full professor at Xiamen University. At present, his research mainly focuses on water treatment, membrane science and technology, especially liquid gating technology for water, environmental, and energy related applications. In 2018, he became a Chief Scientist of National Key R&D Program (Nanoscience) of China for developing carbon nanotube based membranes for water desalination. In 2020, he became an awardee of the National Science Fund for Distinguished Young Scholars for investigating the liquid gating membranes for water treatment. In October 2020, his leading research field "liquid gating technology" was selected as the 2020 Top Ten Emerging Technologies in Chemistry by International Union of Pure and Applied Chemistry (IUPAC)