The thioaptamers exhibited excellent binding to three human ovarian cancer cell lines—SKOV3 (Sloan-Kettering ovarian cancer-3), IGROV-1 (Institut Gustave Roussy Ovarian cancer-1) and A2780 (ovarian adenocarcinoma), but did not bind to CD44-negative cells, suggesting that they could be useful targeting agents against cancer. The gene discussed is CD44; the disease is ovarian carcinoma.