Microphysiological systems for modelling and monitoring biological barriers
- Autores: Jose Yeste Lozano
- Directores de la Tesis: Rosa Villa Sanz (dir. tes.), Xavier Illa Vila (codir. tes.)
- Lectura: En la Universitat Autònoma de Barcelona ( España ) en 2018
- Idioma: español
- Tribunal Calificador de la Tesis: Eduardo Fernández Jover (presid.), Elena Martínez Fraiz (secret.), Ramón Bragós Bardía (voc.)
- Programa de doctorado: Programa de Doctorado en Ingeniería Electrónica y de Telecomunicación por la Universidad Autónoma de Barcelona
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- Resumen
Microphysiological systems (MPS) are biologically inspired microengineered in vitro models that faithfully recapitulate tissue- and organ-level physiology and emulate physiologically relevant in vivo conditions, such as cell organization and microenvironmental cues. Recent advances in biomaterials and microtechnologies have enabled the development of significant MPS with potential applications in toxicity, disease modelling, and drug development. Current MPS are extremely useful for modelling biological barriers that separate the blood circulation from tissue compartments and that play an important role in the pathophysiology of many prevalent human diseases.
The primary function of a barrier tissue is to control the transepithelial transport of solutes; therefore, the ability to quantify transport in a barrier model is critical. Electrical impedance spectroscopy (EIS) permits its quantification with the advantages of being non-destructive, label-free, and easily applicable in real time. However, it is challenging to achieve the uniform current distribution required for accurate measurements within miniaturized cell culture channels of MPS, which can partially explain the large disparity of transepithelial electrical resistance (TEER) values reported for identical cell types. Here, a numerical study is presented to elucidate this issue and to optimize a tetrapolar configuration especially suitable for performing accurate EIS measurements in microfluidic channels, in which cells can be visualised alongside TEER analysis since it implements minimal electrode coverage. Based on this optimal configuration, it was developed a modular perfusion chamber made of a disposable porous membrane, where the barrier tissue is formed, and two reusable plates, where electrodes are patterned. Additionally, with the same electrodes but in a bipolar configuration, the concentration of NaCl in both sides of the tissue can be estimated from electrical conductances of the solutions—enabling in-line measurement of the transepithelial chemical gradient of NaCl. This measurement system was validated using an in vitro model of the renal tubule, which is physiologically exposed to transepithelial gradients as a result of its continuous transepithelial transport of NaCl.
Beyond the capabilities of membrane-based compartmentalization strategies, the development of MPS with multiple interconnected biological barriers will expand the technology to recapitulate more complex organ-level functions. There are multiple technical challenges to reproduce several biological barriers in a single device while maintaining a particular controlled microenvironment for each cell type. Here, it is presented a novel microfluidic device where 1) multiple cell types, arranged in side-by-side compartments, are interconnected with microgrooves and where 2) multiple barrier tissues are measured through metal electrodes in the microgrooves. As a proof-of-concept, the device was used to mimic the structure of the blood-retinal barrier (BRB) including the inner and the outer barriers. Both barriers were successfully formed in the device and monitored in real time, demonstrating its great potential for application to organ-on-a-chip technology.
