Identification of drug-resistant cells with the fluorescent AuNCs based sensing platform. Canonical score plot for fluorescence response patterns against cells (1000 cells): MDA-MB-231 cells, doxorubicin resistant MDA-MB-231 cells (MDA-MB-231(DR)), MDA-MB-231 cells treated with doxorubicin (MDA-MB-231+DOX), MDA-MB-231(DR) cells treated with doxorubicin (MDA-MB-231(DR)+DOX), MDA-MB-231 cells treated with fluorouracil (MDA-MB-231+5-FU), MDA-MB-231(DR) cells treated with fluorouracil (MDA-MB-231(DR)+5-FU).