Sensitive electrochemical aptasensor for detecting EpCAM with silica nanoparticles and quantum dots for signal amplification

The epithelial cell adhesion molecule (EpCAM) is a known biomarker of circulating tumor cells that plays an important role in tumor metastasis. The detection of EpCAM is vital for personalized diagnosis and therapy but is challenging because of its extremely low concentration in peripheral blood. In our work, an electrochemical aptasensor has been developed to quantitatively detect EpCAM at low concentrations. A gold electrode modified with an aptamer can capture EpCAM, which can then be further recognized by a second aptamer acting as a signal reporter. To amplify the signal, a silica nanoparticle/CdSe complex has been designed to enhance the detection system. First, silica nanoparticles were synthesized to act as carriers for loading many CdSe quantum dots which are capable of binding with the second aptamer by biotin-streptavidin interactions. A molecule of EpCAM can bind with numerous CdSe quantum dots (QDs) to realize significant signal amplification. By stripping square wave voltammetry (SSWV), concentrations down to 10 aM EpCAM can be successfully detected and quantified based on the newly developed aptasensor. The detection linear range is from 10 aM to 100 pM. This principle can also be extended to other biomarkers when a suitable aptamer or antibody is available. This aptasensor is expected to be a potential tool for the diagnosis, therapeutic evaluation and personalized medical care of cancer patients. The signal amplification aptasensor for detecting low-level EpCAM was fabricated by the immobilized aptamer capturing EpCAM with the silica nanomaterial which can load numbers of aptamer-binding quantum dots. [Display omitted]