Rotating Magnetic Field-Enabled Metasurface-Regulated Luminescence Strategy for Extracellular Vesicle Detection

Metasurface was a 2D array of subwavelength artificial structures capable of regulating nanoscale optical fields. Although the metal-based metasurface exhibited notable localized field enhancement effects, its static optical responses and ohmic losses limited further development. Magnetic field tuning offered a noninvasive means to dynamically reconfigure the optical functionalities of metasurface. Electrochemiluminescence (ECL), known for its spatiotemporal controllability and low background, can be regulated by the metasurface, which allows for highly spatially selective ECL enhancement with excellent system stability. In this work, we developed a dynamically responsive metasurface system by combining a rotating magnetic field with a Au nanorods (Au NRs)-based metasurface. To provide a stable and efficient light source for the metasurface, zinc-based metal-organic frameworks incorporating polyoxometalates (POM@Zn-MOF) were employed as novel ECL emitters. The multielectron-transfer property of POM optimized interfacial electron transport pathways, thereby enhancing the ECL activity of the MOF. The metasurface exhibited dual surface plasmon modes and strong local electromagnetic fields. Importantly, the electromotive force induced by the rotating magnetic field in the Au NR dynamically tuned the near-field enhancement effect and polarization response properties of the metasurface. As a result, both the ECL intensity and emission polarization states were effectively regulated, leading to improved analytical sensitivity and spatial resolution. Finally, an ECL sensing platform was established using the rotating magnetic field-tuned metasurface system together with a dual membrane protein labeling strategy for the sensitive and specific detection of gastric cancer-derived extracellular vesicles (EVs).