A smart nanoDDS consisting of quercetin, a mild P-gp efflux inhibitor, adsorbed on the nanoconjugate of N-desmethyl tamoxifen (Figure 6) with MWCNT–COOH mediated by tetraethylene glycol linker was prepared by Kumar et al. [291] At physiological conditions, the in vitro release of N-desmethyl tamoxifen from the conjugate was negligible compared with the free drug; however, it was considerably enhanced at an acidic pH corresponding to the microenvironment of cancer cells. The gene discussed is PGP; the disease is cancer.