PGP and neoplasm: Encapsulation of paclitaxel with P-gp modulator tariquidar in poly (D, L-lactide-co-glycolide) nanoparticles functionalized with biotin revealed higher in-vitro cytotoxicity and increased intracellular accumulation compared to paclitaxel nanoparticles alone in drug-resistant tumor cells to overcome tumor drug resistance through biotin receptor-mediated endocytosis (Patil et al., 2009a).