Inflammatory response in tissues surrounding the subcutaneously implanted hydrogels. M&T staining of the S (A), S + P (B), S + B + K (C) and S + B + K + P (D) hydrogels. H&E staining of the S (E, I), S + P (F, J), S + B + K (G, K) and S + B + K + P (H, L) hydrogels. Scale bars = 600 μm in (A–D); Scale bars = 200 μm in (E–H); Scale bars = 40 μm in (I–L). ∗ represents hydrogels; arrows represent drug-loaded SF microspheres.