LAUSR

&NA; Estrogen receptor alpha (ER&agr;) also known as NR3A1 (nuclear receptor subfamily 3, group A, member 1) is a ligand‐activated transcription factor. It is an important biomarker for breast cancer metastasis. In the present study, we report a novel DNA aptamer candidate against estrogen receptor (ER) alpha structure. The enriched aptamer candidate was obtained after 14 iterative cycles of in vitro protein‐SELEX process. Isothermal calorimetry study suggests the nanomolar sensitivity of the candidate ER_Apt1 to its target protein. Fluorescence‐ and chemiluminescence‐binding assays confirm the specificity of the candidate aptamer to ER alpha positive breast cancer cell line. Comparative analysis of ER_Apt1 to ER alpha monoclonal antibody was also performed to analyze the expression of ER alpha in various malignant cancer cell line. Cytochemical and immunohistochemistry assay indicates its potential use as a diagnostic agent against ER&agr; positive carcinomas. The nucleotide aptamer sequences described in the present study can be used for the detection, treatment, prophylaxis and diagnosis of ER&agr;‐related disorder.