Timescale analysis for estimating upper limit perfusion rate in a microfluidic perfusion cell culture platform

Proliferation characteristics of CHO-K1 cells were investigated under a variety of medium perfusion rate conditions in a microfluidic perfusion cell culture platform. Five microcavities of \(800\,\upmu \hbox {m}~(w)\,\times \,800\,\upmu \hbox {m}~(l)\,\times \,400\,\upmu \hbox {m}~(h)\) were adopted in order to minimize or isolate the shear effects on cell surfaces. Microchannels of \(800\,\upmu \hbox {m}~(w)\,\times \,3.5\,\hbox {mm}~(l)\,\times \,100\,\upmu \hbox {m}~(h)\) serially connecting these microcavities created flow contractions and expansions repeatedly, resulting in two different diffusion and convection timescales through the platform. Average shear stresses on the bottom of microcavity were both numerically and analytically estimated, and medium flow was operated at rates where shear stress is below \(\sim\)2 mPa. Proliferation rates of CHO-K1 cells were investigated based both on population groups derived from the number of initially seeded cells and on the microcavity locations. Population groups showed minimal influences on proliferation rates, while proliferation rates increased clearly with medium perfusion rates. Strong effects of microcavity locations were observed on proliferation at \(\hbox {Pe}\,\ge \,45\). Such effects were analyzed by investigating the relationships of reaction, diffusion, and convection timescales associated with perfusion conditions. The ratio of diffusion timescale and convection timescale was suggested as a guideline to estimate the upper limit of perfusion rate in microfluidic perfusion cell culture platform.