ERBB2 and breast cancer: The in vitro binding efficiency and selectivity was assayed through flow cytometry and fluorescence microscopy on SK-BR-3 cells, HER2-positive (HER2+) breast cancer cells, and HER2-negative (HER2-) MDA-MB-468 cells, using SiNP-NTA-TZ and partially functionalized NPs (SiNP-NTA, SiNP-TZ, and SiNP).