Scalable In Vitro Blood-Brain-Barrier Models for Biological and Pharmaceutical Research

Abstract

This thesis presents the design, realization, characterization and application of microfluidic-based in vitro blood-brain-barrier models recapitulating an in vivo-like three-dimensional (3D) cellular organization and physiological environment to investigate the barrier response to external insults and to screen for BBB-permeable compounds against central nervous system (CNS) diseases. The high selectivity of the BBB maintains brain homeostasis, however it also poses a major roadblock in the effective delivery of drugs and therapeutics to treat CNS diseases. Barrier exclusion of therapeutics from the brain is among the main factors behind the high attrition rate of brain-targeted therapeutics. Therefore, investigating the ability of new drugs to cross the BBB during drug development will help in finding new treatment options for CNS diseases. Compared to widely used in vivo animal models, in vitro models offer lower costs, higher throughput, and the possibility to use human-based cellular models, which reduces potential issues related to species-dependent differences between human and animal BBB models. In addition, advanced in vitro models have been instrumental in reducing animal use and expedite drug development. In this thesis, two open-microfluidic platforms to realize 3D BBB models to study barrier responses to external insults and the barrier permeability to chemotherapeutics have been developed: (i) A human-cell-based blood-brain-barrier platform with integrated, transparent electrodes to monitor barrier tightness in real time via impedance and high-resolution imaging. The platform was used to investigate how the barrier reacts to external injury events, such as an ischemic insult. Electrical measurements showed a rapid decrease of the barrier electrical resistance before the appearance of actin stress-fiber bundles during the ischemic insult. (ii) A microfluidic high throughput, open-microfluidic BBB model fabricated in standard plastic material, combined with a 3D-cell culture-based tumor model platform for drug screening. The platform was used to evaluate the delivery of candidate compounds into the CNS and the efficacy of the compounds against the tumor and their toxicity on healthy cells. The developed platforms feature dynamic 3D in vitro BBB models to improve the understanding of the role of the BBB in CNS diseases and to advance the identification of therapeutics for brain diseases. The models offer the possibility to elucidate intricate mechanisms underlying the pathogenesis of CNS diseases and to facilitate the identification of potential therapeutics for brain disorders. The developed platforms exhibit high sensitivity and resolution in detecting BBB reorganization. They allow for mid-to-high throughput screening, making these platforms an attractive tool for biological and pharmaceutical research. Taken together, the developed platforms represent a significant advancement and have the potential to pronouncedly enhance our understanding of BBB biology and CNS disease pathology.