Mineralization of Dandelion as an Enzyme-like Nanoelectrode for Ultrasensitive Monitoring of H2O2 at a Single-Cell Level

Cellular heterogeneity is one of the major challenges in understanding cell-to-cell differences in therapeutics. A sensitive electrode with a micro/nanoscale diameter is urgently needed for sensing molecules at a single-cell level. A dandelion seed has a bristly fiber structure and measures roughly 14 mm. Inspired by this, a solid-state electrochemiluminescence (ECL) nanoelectrode based on a dandelion seed is developed for the ultrasensitive analysis of H2O2. A layer of gold nanoparticles is electroless-plated on the dandelion seeds to enable the bio-fibers to work as conductive electrodes. Because ECL is a surface-confined process, a layer of MIL-100(Fe) (MIL = Materials of Institut Lavoisier) film is coated on the fiber electrode as the carrier of a luminophore. Benefitting from the peroxidase-like activity of an iron(III) metal-organic framework (FeMOF), H2O2 is decomposed into •OH radicals, which in situ serve as the coreactants for the ECL emission. The design of this luminophore-in-MOF coater not only shortens the distance between the detection interface and the coreactant molecules but also effectively enriches the excited-state luminophore in a localized thin film. As a proof of concept, the nanosized filament tips are employed to sense the H2O2 released from different living cells at a single-cell level and demonstrate excellent feasibility in probing the cell heterogeneity. As a biomass electrode, the superiority of a dandelion nanoelectrode is that it is inexpensive, scalable, assessable, and environmentally friendly. This study not only advanced plant fibers as conductive nanoelectrodes but also, more importantly, offered access to the development of solid-state ECL nanoelectrodes with single-cell sensitivity.