Fig. 4.

Electron micrographs of PSI-containing microspheres reveal surface characteristics. All images were captured using the Zeiss Auriga Dual Beam FIB/SEM, and all samples were sputter-coated with Au before imaging. All samples were at a BSA:PSI ratio of 500:1. A. An electron micrograph showing the difference between cubic calcite and spherical vaterite CaCO₃ particles. B. PSI-containing microspheres before cross-linking. C. PSI-containing microspheres after cross-linking. D. A close-up of the same sample from D showing the difference in texture between the CaCO₃ template and the protein encased. E. PSI-containing microspheres after chelation of the CaCO₃ template. F. An example of a rare hollow microsphere after chelation. Nearly all microspheres are solid throughout as shown in Fig. 1.