Microfluidic device for cell culture, metabolite analysis and cytotoxicity assay. (a) The integrated microfluidic device. (b) Microchannels for HLM encapsulation by PEG hydrogels. (c) Design of the on-chip micro-SPE column. (d) Cell culture channel. (e) An image of the microfluidic device filled with a blue dye in the bioreactor part cell culture part. Reproduced from Mao, S.; Gao, D.; Liu, W. et al. Lab Chip, 2012, 12, 219–226 (ref 58), with permission, copyright Royal Society of Chemistry, 2012.