MUC1 and breast cancer: As a result, the Aptamer-Td complex could selectively bind and deliver Dox to MUC1-positive breast cancer cells, demonstrating significantly higher cytotoxicity towards MUC1-positive MCF-7 breast cancer cells compared to MUC1-negative control cells in vitro (P < 0.01), suggesting a promising drug delivery system for the targeted therapy of MUC1-positive breast cancer.