Tumor spheroid growth: ultra-low attachment (ULA) 96-well round-bottomed plates vs agar-coated 96-well flat-bottomed plates. (a) ULA 96-well round-bottomed plates and agar-coated 96-well flat-bottomed plates were used to generate U-87 MG spheroids (a single spheroid per well). Starting from day 4 post initiation, images were obtained at intervals using an inverted microscope. Analysis was carried out using Image-Pro Analyzer software and growth curves were obtained. Values are means ± SD (n = 16 spheroids/timepoint; a representative result of two independent experiments is shown). (b) Representative images of U-87 MG spheroids grown on ULA plates or on agar-coated plates at the indicated timepoints. Scale bar: 100 μm.