FIG. 1.

Diverse cell models can be chosen depending on the desired level of complexity and type of information. (A) Models involving the study of single cells for obtaining mechanistic information. Single cells can be adherent (a, reprinted with permission from Fan et al., J. Controlled Release 170, 401 (2013). Copyright 2013 Elsevier), trapped in microfluidic structures (b, reprinted with permission from Li et al., Lab Chip 13, 1144 (2013). Copyright 2013 The Royal Society of Chemistry) and mammalian or not (Xenopus oocyte in c, reprinted with permission from Zhou et al., J. Controlled Release 157, 103 (2012). Copyright 2012 Elsevier). (B) More complete models make use of cell population that can be arranged as a monolayer (a, reprinted with permission from Sridhar et al., PLoS One 9, e93618 (2014). Copyright 2014 Author(s), licensed under a Creative Commons Attribution 4.0 License.⁷⁹) or be in suspension (b, reprinted with permission from Tandiono et al., Lab Chip 12, 780 (2012). Copyright 2012 The Royal Society of Chemistry) in order to learn about the cell behavior in a collaborative context. (C) More complex bottom-up models are developed in which the cells are placed in a 3D environment, that is more similar to the in vivo situation. These models can be classified in 3 main categories: cell clusters (a), organs-on-a-chip with fully developed blood vessels (b, reprinted with permission from Moya et al., Tissue Eng., Part C 19, 730 (2013). Copyright 2013 Mary Ann Liebert, Inc. publishers), and biofilms (c, reprinted with permission from D. J. Stickler, Nat. Clin. Pract. Urol. 5, 598 (2008). Copyright 2008 Macmillan Publishers Ltd.⁸⁰), which are particularly used to optimize cleaning processes. (D) Some ex vivo models were also used to study bubble-cell interactions such as excised tissues (a, reprinted with permission from Chen et al., Appl. Phys. Lett. 101, 163704 (2012). Copyright 2012 AIP Publishing LLC) or a chicken egg embryo (b, reprinted with permission from Faez et al., Ultrasound Med. Biol. 38, 1608 (2015). Copyright 2015 Elsevier) to which regulatory restrictions do not apply.