Fig. 2

NV@CaP-RGD significantly increased the intracellular concentration of drugs in MCF7 and MCF7/MDR cells. a, b Fluorescence images of Calcein AM. The intracellular relative Calcein fluorescence in the NV@CaP-RGD group was significantly stronger than that in the control groups. As a substrate of efflux pump proteins, strong Calcein AM fluorescence indicates a significant inhibitory effect on the function of efflux proteins and more drugs remaining in the tumor cells. c, d The inverted fluorescence microscope technique assessed the internalization of the NPs. In MCF7 and MCF7/MDR cells, the amount of drugs loaded by NPs-RGD internalized by the cells was much greater than that of the unbound drugs and NPs. Over time, the amount of NPs internalized by the cells significantly increased. e and f The concentrations of VRP and NVT in MCF7 and MCF7/MDR cells were detected using HPLC. Compared to the NV@CaP-RGD and unbound VRP and NVT groups, NV@CaP-RGD substantially increased the intracellular concentrations of NVT and VRP (***P < 0.001)