HeLa cells were treated with cisplatin at selected concentration levels (0 to 100 μM) for a specified incubation time (ranging from 0 to 96 h). After the drug treatment, cells were incubated with propargyl choline (2 mM in regular cell culture medium) for 1 h at 37°C. Propargyl choline labeled cells were rinsed with PBS and fixed using formaldehyde (3.7% in PBS) at 4°C. After 30 min of fixation, cells were rinsed with PBS and incubated with the click chemistry reaction buffer for 30 min in the dark at room temperature. This reaction buffer contains 0.1 M Tris-Buffer (), 0.05% Triton, 10 μM Alexa-488 azide, 1 mM , and 50 mM Ascorbic Acid. After the click chemistry reaction, cells were rinsed and imaged using an inverted fluorescence microscope (IX71, Olympus Inc., Center Valley, PA). Excitation and emission filters for fluorescence microscopy were and 520 to 550 nm, respectively. Exposure time of the CCD camera (charge-coupled device, Hamamatsu Photonics, Bridgewater, NJ) was 500 ms for fluorescence imaging of cells. Multicellular spheroids were treated with a fixed concentration of cisplatin for 48 h prior to incubation with propargyl choline using the same procedure as described above for the 2-d cell culture models. Multicellular spheroids were imaged using a Zeiss LSM 510 confocal microscope (Carl Zeiss, Inc., Thornwood, NY) with 488 nm laser excitation and a band pass emission filter (520 to 550 nm).