Microfluidic chip based OoC’s. The design of microfluidic OoCs enables control over the cellular microenvironment to create more physiologically and relevant cell models. This is in contrast with the traditional way of static cell culture systems and bioreactors. The development of microfluidic OoC systems has mainly relied on the interdisciplinary cooperation between the engineering community and biologists. Although these interactions have been widely successful, there have been issues and a mismatch between materials that engineers can easily prototype and materials that biologists are familiar with (Xxxxxxxx, Xxxxx, and Xxxxx 2012). Microfluidic fabrication is most commonly carried out with elastomers. Polydimethylsiloxane (PDMS) is the exponent material used for the creation of complex microfluidic devices due to both its ease in prototyping as well as its material properties, such as transparency and oxygen permeability. Microfabrication methods are used to generate soft, flexible and micropatterned structures using soft lithography processes. However, PDMS may influence the experimental results, as it is prone to adsorbing hydrophobic compounds from the solutions into the bulk PDMS (Xxxxxxxx Xx, Xxxxxxxx, and Xxxxxxx- Xxxxxxx 2009). Biologists have predominantly used glass and polystyrene (PS) to build substrates and for this reason, they do not have much experience with PDMS. The use of PS has dominated cell culture applications since the 1960s due to its low cost, optical clarity, durability, and mechanical strength. Even though glass and PS are harder and more brittle than PDMS, devices from these materials do not have the same limitations as PDMS, including hydrophobic adsorption, evaporation, and leaching of uncrosslinked polymers. Unfortunately, the production of microfluidic devices based on thermoplastic polymers and glass is more complex than when PDMS is used. These devices can be produced at low-cost by large-scale fabrication but prototyping is more costly. Therefore, thermoplastic polymer based OoC’s are currently less widely investigated than PDMS-based. The complexity of microfluidic OoC depends on the cell type and architecture of the microfluidic chip. The simplest OoC models contain only a single cell type in a straight microfluidic channel. The microchannel surfaces may be coated with hydrogels to improve cell adhesion and proliferation. Despite the simplicity of the microenvironment, such devices have interesting applications for studies on vascular (X. Xxx et...
