Recently, Professor Cai Bin's team at the School of Chemistry and Chemical Engineering has developed a highly sensitive glucose electrochemical sensor. This novel sensor employs a copper hydroxide-organic framework material (Cu-MHOF) as the sensing layer. During the detection process, it successfully achieves the complete oxidation of glucose molecules, significantly enhancing the signal amplification of each molecule. Based on this, a portable wireless glucose sensor has been developed for monitoring the dynamic changes of glucose in human body fluids. This paper, entitled "Complete Glucose Electrooxidation Enabled by Coordinatively Unsaturated Copper Sites in Metal-Organic Frameworks", is published in Angew. Chem. Int. Ed., and being selected as a VIP paper. Professor Cai Bin and Professor Yuan Shuai (Nanjing University) are the corresponding authors. Dr. Shi Xiaoyue, postdoctoral researcher at Shandong University, is the first author.

Non-invasive real-time monitoring of biomarkers, such as glucose, is crucial for disease prevention, diagnosis, and health management. Taking glucose sensor as an example, the detection relies on the signal (or electrons) generated by the glucose oxidation reaction (GOR). Current sensing materials undergo a 2-electron oxidation process, limiting the improvement of sensitivity. Glucose, a multicarbon substance, can undergo complete oxidation, releasing up to 24 electrons. However, achieving complete oxidation remains a challenging goal.

Figure 1. Mechanistic overview of the electrochemical oxidation of glucose

As shown in Figure 1, Cu(OH)₂ possesses a natural advantage in catalyzing glucose oxidation. It can spontaneously catalyze glucose oxidation through instantaneous thermal catalysis, releasing 2 electrons. In this study, a Cu-MHOF catalyst was designed by connecting Cu(OH)₂layers with aromatic carboxylic acid ligands. The aromatic ligands in Cu-MHOF exhibit strong π-π interactions, enhancing the structural stability while exposing numerous unsaturated Cu sites. During the GOR process, unsaturated Cu sites, in coordination with aromatic ligands, play a crucial role in adsorbing reactants and intermediates, facilitating the complete oxidation process. Compared to Cu(OH)₂ nanomaterials, Cu-MHOF shows an approximately 40-fold increase in the oxidation-sensing signal for glucose. This work also employs isotope labeling and other methods to carefully investigate the deep oxidation mechanism of glucose.

Figure 2. Design of miniaturized glucose sensor and its performance

Due to the enhanced electrocatalytic performance, this team, in collaboration with Shenzhen Refresher Biosensing Technology Co., Ltd., has designed and developed a portable Cu-MHOF glucose electrochemical sensor. This device, with a length of less than 10 cm, enables sensitive detection of low-concentration glucose. As shown in Figure 2, the Cu-MHOF glucose sensor exhibits excellent sensing performance, successfully achieving dynamic monitoring of human saliva.

Figure 3. Conceptual illustration of the non-invasive glucose monitoring system

The non-invasive glucose monitoring system based on the aforementioned electrochemical sensor (Figure 3) primarily consists of three main components: the client-side (APP), cloud, and relevant hardware devices. The system is user-friendly, allowing control and operation through a smartphone or tablet. Test results can be recorded and queried in real-time through the mobile device and synchronized with the cloud. Remote healthcare professionals can provide medical guidance based on the cloud-based test results, and users can adjust their diet or medication according to the test results and medical advice.

Link to the article:https://onlinelibrary.wiley.com/doi/10.1002/anie.202316257

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