Fig. 4: Microscopic characterization of chitosan-alginate core-shell microspheres.

a The SEM image demonstrates the high sphericity of the microspheres. b SEM cross-sectional image showing the distinct boundary between the chitosan core and alginate shell, highlighting the well-defined core-shell morphology. c BF optical micrograph of a single microsphere, illustrating its uniform shape of core and shell. d Optical micrograph of a dissected microsphere, revealing the internal core and shell structure