2D metal azolate framework as nanozyme for amperometric detection of glucose at physiological pH and alkaline medium.

Abstract

Thesynthesis of Co-based two-dimensional (2D) metal azolate framework nanosheets (MAF-5-CoII NS) is described usinga simple hydrothermal method. The product was isostructural to MAF-5 (Zn). The as-prepared MAF-5-CoII NS exhibited high surface area (1155m2/g), purity, and crystallinity. The MAF-5-CoII NS-modified screen-printed electrode (MAF-5-CoII NS/SPE) was used for nonenzymatic detection of glucose in diluted human blood plasma (BP) samples with phosphate buffer saline (PBS, pH7.4) and NaOH (0.1M, pH13.0) solutions. The MAF-5-CoII NS nanozyme displayed good redox activity in both neutral and alkaline media with the formation of CoII/CoIII redox pair, which induced the catalytic oxidation of glucose. Under the optimized detection potential, the sensor presented a chronoamperometric current response for the oxidation of glucose with two wide concentration ranges in PBS-diluted (62.80 to 180μM and 305 to 8055μM) and NaOH-diluted (58.90 to 117.6μM and 180 to 10,055μM) BP samples, which were within the limit of blood glucose levels of diabetic patients before (4.4-7.2mM) and after (10mM) meals (recommended by the American Diabetes Association). The sensor has a limit of detection of ca. 0.25 and 0.05μM, respectively, and maximum sensitivity of ca. 36.55 and 1361.65mA/cm2/mM, respectively, in PBS- and NaOH-diluted BP samples. The sensor also displayed excellent stability in the neutral and alkaline media due to the existence of hydrophobic linkers (2-ethyl imidazole) in the MAF-5-CoII NS, good repeatability and reproducibility, and interference-free signals. Thus, MAF-5-CoII NS is a promising nanozyme for the development of the disposable type of sensor for glucose detection in human body fluids. Graphical abstract.