Thermally Modulated Metasurface Sensor for Dynamic and Time-Resolved Isolation of Extracellular Vesicles

Extracellular vesicles (EVs) are nanoscale lipid-bilayered structures that mediate intercellular communications by transporting nucleic acids, proteins, and lipids across diverse biological fluids. Their diagnostic potential is immense, yet their heterogeneity poses persistent challenges for isolation and characterization, often leading to low yield, co-isolation of contaminants, and vesicle damage. Here, we present a thermoresponsive polymer-integrated plasmonic metasurface sensor that enables spatiotemporally controlled, label-free EV isolation. The metasurface, engineered by repurposing nanograted optical disks, was functionalized with poly(N-isopropylacrylamide) (PNIPAM) and anti-CD63 antibodies to achieve selective EV capture at physiological temperature and gentle release upon a minute thermal change near the polymer's lower critical solution temperature (∼35°C). Using MCF-7 and HEK-293-derived EVs as a proof-of-concept, the platform exhibited a dynamic detection range spanning three orders of magnitude. Release efficiency reached 87.03 ± 23.5%, while both nanoparticle tracking analysis (NTA) and fluorescent NTA (fNTA) revealed up to ∼100-fold increase in EV purity relative to the ultrafiltration process. Electron microscopy and Western blotting confirmed preserved vesicle morphology and marker expression. By integrating thermoresponsive chemistry with a cost-effective metasurface platform, this system offers a non-destructive, portable, and real-time solution for precise EV manipulation, advancing EV-focused biosensing and point-of-care strategies for liquid biopsy applications in the future.