Effect of inoculum concentration in NT2 cell expansion as 3D-aggregates. Cells were cultured in spinner vessels with inoculum concentrations of 0.4 (SP-0.4B, squares), 1 (SP-1B, circles) and 4 (SP-4B, triangles) ×105 cell/mL. Phase contrast photomicrographs of cultures samples visualized by day 1, day 3 and day 6 of cultivation. Scale bar: 100 μm (A). Growth curves expressed in terms of cell concentration; error bars denote standard deviation of average from 2 independent experiments (B).