Figure 3.

Equilibrium separation and analysis of LNCaP EpCAM distribution in a gradient pitch array. (a) A stitched image is shown of magnetically labeled LNCaP cells equilibrating at different pitches within a 2μm incremented chip driven at 5Hz frequency. Insets show cells equilibrating at pitches according to quantity of particles per cell (PPC). (b) The graph plots the PPC versus the on-chip location and critical pitch of individual cells (points). The theoretical 1/3 power relationship between PPC and pitch is shown as a solid line. Five statistically significant (p<0.05) populations were identified ranging from 1–25, 22–46, 40–70, 83–123 &130–180 particles per cell with corresponding averages (black circles). Each subpopulation equilibrated at increasing horizontal pitches, correlating well with the theoretical model (R²=0.91). (c) Independent of the attached particle number, the cell distribution as a function of pitch for both chips is also shown (N=508). (d)The PPC distribution of magnetically labeled LNCaP cells is also plotted for a 10μm incremented chip at 5Hz, again correlating with the predicted model (R²=0.89). More punctate trapping is observed due to the coarseness of the pitch gradient and additional populations of more strongly labeled cells are observed compared to the 2μm incremented chip. (e) The cell distribution as a function of pitch for this chip is also shown.