(a) Three-dimensional scheme of alginate-protamine sulfate-alginate (APSA) microcapsule containing GadoGold (GG). The semi-permeable microcapsule allows diffusion of oxygen, nutrients, glucose, and insulin, while the passage of immune cells and antibodies is blocked. (b ,c) Light microscopic images of the APSA-GG microcapsule 1 h (b) and two days (c) after synthesis. (d) Human pancreatic islet inside the APSA-GG microcapsule. (e) Fluorescence microscopic image shows viability staining of mouse insulinoma β-TC-6 cells inside the APSA-GG microcapsule. Green (fluorescein diacetate stain)=live cells, red (propidium iodide stain)=dead cells. Scale bars=200 mm. Reproduced, with permission, from Ref. [270].