Rational Assembly of Polymer-Metal Coordination Hierarchical Superstructures for Azathioprine-Responsive Electrodes in Biological Samples

The sustainable self-assembly of small molecules into a superstructure is of prevalent interest for particle engineering and its applications. Herein, a ligand-metal cross-linking chemistry strategy is developed for the design of molybdenum-polydopamine (Mo-Px) coordination flowers and their electrochemical sensing performance. The morphology of Mo-Px can be easily tuned by adding surfactants such as cetyltrimethylammonium bromide (CTAB) and sodium lauryl sulfate (SLS). This coordination polymerization is a rapid, single-step approach to producing functional materials and offers excellent control over the formation of flower-shaped superstructures. The devised Mo-Px (namely, x = H2O, CTAB, SLS) superstructures were applied as electrode materials to study the electrocatalytic activity of azathioprine (AP). Having the advantages of a hierarchical superstructure, including a great electroactive surface area, rapid electron transfer, interconnected nanosheet-based architectures, and Mo doping, the as-obtained Mo-PSLS served as a high-performance electrocatalyst in a AP sensor and unveiled great sensitivity (6.13 μA μM-1 cm-2), a low detection limit (3.5 nM), and good operational stability. Additionally, a Mo-PSLS-modified electrode was successfully utilized to monitor the AP concentration in actual rat blood serum samples with satisfactory recovery results. This work paves the way for the design of ligand-metal coordination complex superstructures for electrocatalyst-based applications.