(a) LSCM images (taken from the same field of microscope) of spherical particles mixed with two fluorescently labelled proteins (BHb* and BSA*, appear magenta and green in the fluorescence images, respectively). Top left, fluorescence image from channel 1 (magenta) shows BHb*-encapsulated particles; top right, fluorescence image from channel 2 (green) shows that no BSA* was adsorbed into the particles; bottom left, transmission image; bottom right, overlay of the three images, showing that only BHb* was adsorbed into the negatively charged particles. This selective separation of BSA* and BHb* at pH 5.8 was confirmed by simultaneous two-colour imaging of particles. Scale bars represent 10 μm. (b) Schematic of the selective separation process of BSA (green ellipsoid) and BHb (magenta sphere) using the particle at pH 5.8. (c) A single particle was imaged by z-slice imaging. The cross-sectional pictures are shown in series from the top of the particle (top left fluorescence image 1) to the bottom (bottom right fluorescence image 8), clearly indicating the three-dimensional, non-hollow nature of the structure. The imaged particle is about 2 μm in diameter.