PGP and cancer: Anti-p-glycoprotein (Pgp)-functionalized MWCNTs, with a distearoyl-sn-glycero-3-phosphoethanolamine-polyethylene glycol5000-maleimide linker, had an excellent intratumor diffusion and Pgp-specific cellular uptake, as well as a potent phototoxicity in tumor spheroid-composed MDR cancer cells [126].