Embodiments described herein generally provide for the expansion of cells in a cell expansion system using an active promotion of a coating agent(s) to a cell growth surface in some embodiments. A coating agent may be applied to a surface, such as the cell growth surface of a hollow fiber in a bioreactor, by controlling the movement of a fluid in which a coating agent is suspended, by changing flow rates, by changing flow directions, by rotation of the bioreactor, and/or combinations thereof.