a, An overview of the step-wise protocol to generate Pd-ExoA549 from A549 cells. b, Representative TEM images of ExoA549 and Pd-ExoA549 at different magnifications. c, Representative cryo-TEM images of Pd-ExoA549 at two magnifications. d, A HRSTEM–HAADF image of a representative Pd-ExoA549. e, A magnified HRSTEM–HAADF image that shows highly crystalline Pd nanostructures with d-spacing of 0.23 nm that corresponds to Pd(111) surfaces. The inset shows the fast Fourier transform spectrum generated from the image. f, Western blots of exosome-specific biomarkers ALIX, CD63, CD81 and CD9 of ExoA549 and Pd-ExoA549.