Detection of oncoprotein platelet-derived growth factor using a fluorescent signaling complex of an aptamer and TOTO

There have recently been advances in the application of aptamers, a new class of nucleic acids that bind specifically with target proteins, as protein recognition probes for biomedical study. The development of a signaling aptamer with the capability of simple and rapid real-time detection of disease-related proteins has attracted increasing interest. We have recently reported a new protein-detection strategy using a signaling aptamer based on a DNA molecular light-switching complex, Ru(phen)₂(dppz)]²⁺. In this work we have used the commercially available DNA-intercalating dye, TOTO, to replace Ru(phen)₂(dppz)]²⁺ for detection of oncoprotein platelet-derived growth factor BB (PDGF-BB), a potential cancer marker. Taking advantage of the high affinity of the aptamer to PDGF-BB and the sensitive fluorescence change of the aptamer–TOTO signaling complex on protein binding, PDGF-BB was detected in physiological buffer with high selectivity and sensitivity. The detection limit was 0.1 nmol L⁻¹, which was better than that of other reported aptamer-based methods for PDGF-BB, including that using Ru(phen)₂(dppz)]²⁺. The method is very simple with no need for covalent labeling of the aptamer or probe synthesis. It facilitates wide application of the signaling mechanism to the analysis and study of cancer markers and other proteins.