Tumors in patients with triple-negative breast cancer (TNBC) are nonresponsive to the most common forms of chemotherapy. Researchers recently identified two small endogenous microRNA molecules (miRs) that differentially regulate tumor progression in TNBC. Delivery of antagonistic or complementary miRs to control these targets holds potential to treat TNBC, but a lack of stability in the body limits their therapeutic potential. Conde et al. set out to design a miR delivery strategy that uses the structure of the miRs themselves in combination with new biomaterials to enhance the stability and efficacy of the miRs.