Optimized Ultrasound Conditions for Enhanced Sensitivity of Molecular Beacons in the Detection of MDR1 mRNA in Living Cells.

P-glycoprotein (P-gp), aprognostic indicator for chemotherapy failure, is encoded by multidrug resistance gene (MDR1). MDR1 mRNA expression could serve as a guidance for personalized medicine. However, the traditional PCR process for mRNA measurement is complicated and cannot realize the real-time detection of mRNA in living single cells. In this work, optimized gold nanoparticle-based molecular beacons were employed to determine MDR1 mRNA levels in living cancer cells. To improve detection sensitivity, ultrasound (US) irradiation was applied to facilitate and enhance cellular uptake of hairpin DNA-coated gold nanoparticle (hDAuNP). The US conditions including irradiation power, exposure time, duty cycle, and incubation time were optimized. The slight difference in MDR1 expression manipulated by siRNA silence could be recognized by US assisted hDAuNP beacons; a 10-fold increase of detection sensitivity was achieved compared with the nonultrasound assistance. Meanwhile, the detection cycle could be shortened from 12 to 2 h. Furthermore, this hDAuNP beacon can serve as an antisense agent to down-regulate P-gp expression and to reverse drug resistance of MCF-7/Adr cells to doxorubicin. Our results demonstrated that the MDR1 hDAuNP beacon assisted by US irradiation had great potential to predict chemotherapy sensitivity and to overcome multidrug resistance in cancer cells and was thus a promising tool for individualized medicine.