(a) (1) TEM of MSNs,28 (2) SEM of SiNPs, (Scale bar = 1 μm).183 (b) Functionalization of MSNs: (1) outer surface, (2) pore entrances, (3) inner walls.160 (c) Micro-CT reconstructed images at 4, 8, and 12 weeks after implantation of (1) zein, (2) zein-HACC, (3) zein-S20, (4) zein-HACC-S20 scaffold. S20 is a type of MSN.210 (d) In vivo US echogenicity of injected MSNs-labeled MSCs. (1) and (3) are pre-injection, (2) and (4) are post-injection. (2) is control and (4) is injection of 500,000 labeled MSCs.88