TF and cancer: Venkatesan et al. covalently linked the mesoporous shell of mesoporous silica nanoparticles (MSNP) to cancer-targeting Tf via disulfide bonds for GSH-controlled DOX drug release in tumor cells.113 They demonstrated that Tf on the surface of MSN selectively recognizes TfR on the surface of cancer cells, enabling MSNP-SS-Tf@PEG to be internalized into HT-29 and MCF-7 cells.