Nonlinear concentration gradients regulated by the width of channels for observation of half maximal inhibitory concentration (IC₅₀) of transporter proteins

This paper describes a simple microfluidic device that can generate nonlinear concentration gradients. We changed the "width" of channels that can drastically shorten the total microfluidic channel length and simplify the microfluidic network design rather than the "length" of channels. The logarithmic concentration gradients generated by the device were in good agreement with those obtained by simulation. Using this device, we evaluated a probable IC₅₀ value of the ABC transporter proteins by the competitive transport assays at five different logarithmic concentrations. This probable IC₅₀ value was in good agreement with an IC₅₀ value (0.92 μM) obtained at the diluted concentrations of seven points.