Figure 3. Comparing the size and shape dependence effects of fibrosis formation on to alginate hydrogels implanted in the subcutaneous dorsal region of non-human primates.

Large 1.5 mm-sized spheres of SLG20 hydrogels implanted subcutaneously in the dorsal region of cynomolgus macaques resist fibrosis, while small spheres (0.5 mm sized) and cylinders (4 mm in diameter and 2 mm in height) become fibrotic. After 14 days, biopsy punches were used to excise implanted materials/peripheral host tissue; upon incision we observed that the large SLG20 alginate spheres were not embedded in host tissue and freely dissociated from the implant site (a). The retrieved large SLG20 hydrogels visually appear to be transparent and void of cellular deposition (b), which was also confirmed using H&E stained histological analysis (c); Scale bar = 500 μm. H&E and Masson’s Trichrome stained histological sections of excised tissue at 14 days (d, Scale bar = 500 μm), and 28 days (e, Scale bar = 500 μm) post-implantation with SLG20 alginate hydrogels formed into large spheres (1.5 mm in diameter), medium sized spheres (0.5 mm in diameter) or cylinders (4 mm in diameter and 1 mm in height), and as well a control saline alone injection (* in images demarks implanted materials). N = 2 for saline and discs; N = 4 for both 0.5 and 1.5 mm sphere groups. These experiments were performed once.