The MTT assay was performed to calculate the toxicity of the probe in mammalian cells. Cells were seeded at 5x10 3 /well and grown in 96-well plates. After 24 h of seeding, the cells were treated with different concentrations (50 and 500 μg/mL) of the NRs, respectively, and incubated for 24 h at 37 °C and 5 % CO2. At the end of this incubation, the medium was removed from all the wells, and the cells were incubated further in fresh growth medium supplemented with 0.5 mg mL -1 of MTT for 4 h. The medium containing MTT was then removed, after which DMSO was added to solubilize the formazan. The absorbance values were recorded using a TECAN Spark plate reader at 570 nm. The cell viability was calculated as the absorbance with respect to the positive control as a reference, in which the cells were treated with triton X-100 at 0.1%. The results presented here are a mean of 8 wells ± standard error. Esterase activity was tested by incubating cells for 30 min at 37 °C in growth medium supplemented with 1 µM of fluorescein diacetate before imaging or flow cytometry analysis. Cell proliferation has been evaluated by first seeding U87 cells in 6 well plates at 1x10 5 cells per wells. After 24 h, nanorods has been added at 50 µg/mL concentration. Three days after seeding, grow medium has been refreshed. For every time points, 3 wells were detached with trypsin-EDTA treatment (5 min at 37 °C) and cells were numbered and they viability check by trypan blue counting on biorad TC20 automated counter.