LAUSR

To enhance the specificity and sensitivity of molecular beacons (MB) in detecting mRNA in living tumor cells, we introduced an aptamer (AS1411) to the delivery system of MB to form aptamer decorated nanoprobe (ANP), which was prepared through self-assembly between AS1411 conjugated carboxymethyl chitosan (ACMC) with protamine sulfate (PS)/CaCO3/MB cores. Owing to the specific binding of AS1411 to nucleolin, which is overexpressed in tumor cell membranes and nuclei, AS1411 decorated MB delivery system leads to dramatically increased cell uptake of MB for probing survivin mRNA and thus induces strong intracellular fluorescence emission in targeted tumorous cells and cell nuclei. Furthermore, we demonstrate ANP can efficiently detect survivin mRNA in mitochondria. In other words, the effective delivery of MB ensures the precise detection of mRNA distribution in diverse organelles. In addition, we evaluated the efficiency of ANP in probing tumor cells in simulated blood as well as in peripheral blood from a healthy donor, and found the nanoprobe can specifically deliver MB to tumor cells and identify tumor cells in blood. The targeting delivery system we constructed holds promising applications in precise detection of subcellular distribution of mRNA in living tumor cells as well as fluorescence-guided cancer detection in liquid biopsy technology. This study provides a facile strategy to effectively improve the specificity and sensitivity of conventional molecular beacons.