Here,we explored the use of functionalized nanoparticles for the detectionof estrogen receptor alpha (ERα) expression in a 3D tumor model,using the ERα-positive human breast cancer cell line MCF-7.This approach was used to compare targeted versus nontargeted nanoparticleinteractions with the tumor model to better understand whether targetednanotags are required to efficiently target ERα. This evidence concerns the gene ESR1 and breast carcinoma.