Fig. 2

Outer membrane vesicle (OMV) purification and characterisation. a Purified form of OMV^WT and OMV^Mel, isolated from parental bacteria by ultrafiltration and ultracentrifugation. b Dynamic light-scattering analysis of OMVs confirmed a particle size distribution in the range of 20 to 100 nm. c Transmission electron micrograph showing the nano-sized (<100 nm), bilayered, circular morphology of OMV^WT and OMV^Mel. Scale bars, 100 nm. d Mean optoacoustic intensity (coloured line) as a function of wavelength for OMV^WT and OMV^Mel