(363f) A Cytometer Capable Of Tracking Suspended Particles In Time

To experimentally determine how the state of a cell population changes over time either a Eulerian or Lagrangian frame of reference can be used. In the Eulerian reference frame one measures the state of an entire cell population at discrete time points. In order to extract the single-cell dynamics from a time series of such measurements it is necessary to solve an inverse problem which in most cases is a non-trivial task. In contrast, in the Lagrangian reference frame one tracks individual cells over time and the dynamic properties of cells directly result from the observations. The properties of the entire cell population are then obtained as the sum of contributions of the individual components.

Traditional flow cytometry is restricted to the Eulerian approach as the measurement yields the cellular property distribution as a snapshot in time and cells are discarded after the measurement. We have developed a new type of cytometer that can track many single cells in suspension consistent with the Langrangian viewpoint. The measurement approach takes advantage of the Segre Silberberg effect that applies when dilute particles are subjected to Poiseuille flow in a capillary. Under such conditions particles of a given size and shape self-organize on the same streamline and keep their relative position in an oscillatory flow regime. We demonstrate that the relative cell order is indeed maintained over extended time periods under such conditions. From the single-cell measurements during each period of the oscillatory flow cycle the single-cell growth rates can be directly extracted. It is anticipated that with further refinements this instrumentation will represent a useful new tool to study cell function during growth and development in highly quantitative terms.