From the cellular perspective: exploring differences in the cellular baseline in macroscale and microfluidic cultures.

Microfluidic devices for cell culture based assays provide new types of engineered microenvironments and new methods for controlling and quantifying cellular responses to these microenvironments. However, without an understanding of the effects of the microenvironments present in microdevices from a cellular perspective, it will be challenging to integrate work done in microdevices with biological data obtained via traditional methods. With the adaptation and validation of In Cell Westerns (ICWs) and in situ analysis techniques to microfluidic devices, we can begin to look at a variety of cellular responses to microcultures. Here we observe several differences in proliferation, glucose metabolism, signaling pathway activation and protein expression levels between cells cultured in traditional macroscale cultures and in microfluidic cultures. The issues of glucose starvation, growth factor restriction, volume density and effects of interactions with poly(dimethylsiloxane) (PDMS) were examined to determine the relative importance of each to cell behavior. Changes in glucose metabolism, insensitivity to volume density or media supplementation, and finally reduced proliferation as the exposure to PDMS increased, suggests that perhaps interactions between media/cells and this commonly employed polymer may be significant for some cell based assays. The differences between cells in macroscale and microfluidic cultures suggest that the cellular baseline may be substantially altered in microcultures due to both inherent differences in scale as well as material differences. The observations highlight the need to biologically validate micofluidic devices for cell based assays in order to accurately interpret the data obtained with them in the context of traditional macroculture data. Additional areas of study that will further characterize and validate microscale culture are discussed.