Biomedical Engineering Reference
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d
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Fig. 5 Chemotaxis of human umbilical vein endothelial cells. a, b Representative phase contrast
images of devices at time = 0 and 6 h under a gradient of 14 ng/ml/mm and average
concentration of 25 ng/mL. The chamber is divided into four equal regions of increasing VEGF
concentration. The arrow points in the direction of the VEGF gradient. c-e The average net
accumulation in the number of cells within each region under three linear concentration profiles,
±standard deviation (n = 3-5 devices). Statistically significant accumulation/depletion of cells,
p \ 0.05. Originally published in [ 30 ]. Reproduced by permission of The Royal Society of
Chemistry, http://dx.doi.org/10.1039/B719788H
regions that ranged in average concentration from 19 to 31 ng/mL and, had identical
gradient steepness (Fig. 5 a, b). Over this concentration range, similar numbers of
cells were observed to chemotaxis in each region. In regions 2 and 3, accumulation
of cells from the region of lower concentration is equal to depletion of cells to the
region of higher concentration; therefore, there is no net change in cell number.
Similarly, depletion of cells from region 1 (with the lowest VEGF concentration)
was equal to accumulation in region 4 (with the greatest VEGF concentration).
Greater average concentration has been theoretically predicted and experimentally
shown to decrease chemotaxis, with sensitivity to the gradient scaling with one over
the square root of concentration [ 67 ]. These results suggest that a higher average
concentration would be required to observe a loss of directed migration in this
system. In addition to the VEGF concentration profile, the density or type of sub-
strate is known to impact 2D migration [ 68 ]. While these experiments utilized a
fibronectin-coated surface, future studies could evaluate chemotaxis on a variety of
 
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