Proximity-constructed bifunctional DNA probes for identification of stem-like biomarker in breast cancer

Abstract CD44, a stem-like biomarker, plays a critical role in maintenance of stem-like phenotype in breast cancer and is associated with migration, invasion and apoptosis resistance of breast tumors. Herein, we designed an effective sensing method using proximity-constructed bifunctional DNA probes for electrochemical identification of CD44. In our design, hybridization of capture probes was stabilized by target CD44 binding-induced proximity, thereby initiating subsequent cyclic strand displacement reactions. As a result, signaling probes were produced and dual-labeled with dibenzocyclooctyne group and CdTe quantum dots (QDs). These signaling probes performed two functions, specifically enrichment on azide-functionalized magnetic beads via click chemistry and generation of amplified electrochemical signaling relied on QDs. With aid of these bifunctional probes, the sensing method allowed not only highly specific identification of target CD44 even in serum samples and breast cancer cells but also monitoring of CD44 expression changes upon siRNA treatment. The linear range for CD44 identification was 0.1–1000 ng/mL and the detection limit was 0.0792 ng/mL, which displayed an improved sensitivity compared to previous reports. Therefore, the method may provide a powerful tool for CD44 identification and have a great potential in revealing stem-like properties in breast cancer in the future.