Multiple Pickering Emulsions Enable Highly Efficient Interfacial Catalysis and Extracellular Vesicle Classification via In Situ Surface-Enhanced Raman Spectroscopy.

Multiple Pickering emulsions show great potential in catalysis and bioanalysis but remain limited by insufficient structural stability, unclear interfacial mechanisms, and limited functional integration. Here, a stable water-in-oil-in-water multicompartment Pickering emulsion was constructed through the synergistic coassembly of polyvinylpyrrolidone-modified gold nanoparticles (Au@PVP) and bovine serum albumin (BSA). The suitable wettability of Au@PVP, together with BSA adsorption and reorganization, promoted the formation of a dense composite nanoparticle film at the oil-water interface, enabling long-term emulsion stability. Using the BSA-catalyzed condensation of chalcone and malononitrile as a model reaction, in situ surface-enhanced Raman spectroscopy (SERS) revealed significantly enhanced interfacial reaction kinetics compared with those in the monolayer emulsion system, with the target product yield increasing by approximately 6.8-fold after 24 h. Fourier transform infrared spectroscopy independently confirmed the kinetic trend. For bioanalysis, replacing BSA with cell-secreted components generated functional emulsion substrates with highly reproducible SERS signals. Combined with feed-forward neural network analysis, the platform achieved classification accuracies exceeding 95% for three types of extracellular vesicles. This multicompartment emulsion platform integrates interfacial engineering, reaction acceleration, real-time monitoring, and intelligent biosensing, providing a versatile strategy for organic catalysis, biomarker detection, and liquid biopsy.