As a biomarker for breast cancer, in addition to creating a method for the growth of AuNBPs mediated by ascorbic acid (AA) that is highly responsive and sensitive to the help of NADH, they developed a very accurate multicolor immunosensor for the highly responsive visual identification of HER2 ECD in serum using AuNBPs as the indicator and an antibody as the recognition agent. This evidence concerns the gene ERBB2 and breast cancer.