Diffusion gradient chemotaxis

As seen in Fig. 1, two main modalities can be distinguished. Cell migration in diffusion gradient chemotaxis assays is mainly dependent on the strength of the chemokine-receptor interaction, but transendothelial... 

Widman, M.T., Emerson, D., Chiu, C.C. and Worden, R.M. (1997). Modeling microbial chemotaxis in a diffusion gradient chamber. Biotechnol. Bioengineer. 55, 191-205. 

Figure 1 Schematic of a chemotaxis experiment. "A" shows a diffusion gradient assay, and "B" shows a transendothelial chemotaxis assay.

Walker GM, Sai JQ, Richmond A, Stremler M, Chung CY, Wikswo JP (2005) Effects of flow and diffusion on chemotaxis studies in a microfabricated gradient generator. Lab Chip 5 611-618... 

To determine the optimal concentration for collecting the invasive population, it is often necessary to perform dose response experiments and try a range of chemoattractant amounts. We have found that for EGF, the optimal concentration in the in vivo invasion assay is 25 nM while for the in vitro Boyden chamber chemotaxis it is 5 nM. The difference can be explained by different diffusion properties of the gradient emanating from a tip of a needle into live tissue vs. EGF in a buffer being directly accessible to migrating cells across pores in a filter. By the same token, the optimal... 

Key words Chemotaxis, Molecular gradients, Collagen gel, Axon guidance, Diffusible factors,... 

In this technique, which is seldom used with bacteria, a stimulant gradient is established by diffusion between upper and lower wells, separated by a polycarbonate membrane [30]. Bacteria are placed in the lower well and a chemoattractant in the upper well. In the case of negative chemotaxis, the chemorepellent is included with the bacteria in the lower well. In either case, the bacteria follow the gradient, swim upwards through the polycarbonate membrane and accumulate in the... 

Kim, M., Kim, T. (2010). Diffusion-based and long-range concentration gradients of multiple chemicals for bacterial chemotaxis assays. Analytical Chemistry, 82(22), 9401—9409. http //dx.doi.org/10.1021/acl02022q. 

Although this assay measures the main feature of CKRs (i.e., chemotaxis), it does not resemble the in vivo situation. For example, the chemokines do not form a gradient in the lower compartment. Furthermore, the chemoattractants diffuse to the upper compartment in time, which ceases cell... 

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