A microfluidic model of human brain (μHuB) for assessment of blood brain barrier

Abstract

Microfluidic cellular models, commonly referred to as “organs‐on‐chips,” continue to advance the field of bioengineering via the development of accurate and higher throughput models, captivating the essence of living human organs. This class of models can mimic key in vivo features, including shear stresses and cellular architectures, in ways that cannot be realized by traditional two‐dimensional in vitro models. Despite such progress, current organ‐on‐a‐chip models are often overly complex, require highly specialized setups and equipment, and lack the ability to easily ascertain temporal and spatial differences in the transport kinetics of compounds translocating across cellular barriers. To address this challenge, we report the development of a three‐dimensional human blood brain barrier (BBB) microfluidic model (μHuB) using human cerebral microvascular endothelial cells (hCMEC/D3) and primary human astrocytes within a commercially available microfluidic platform. Within μHuB, hCMEC/D3 monolayers withstood physiologically relevant shear stresses (2.73 dyn/cm 2 ) over a period of 24 hr and formed a complete inner lumen, resembling in vivo blood capillaries. Monolayers within μHuB expressed phenotypical tight junction markers (Claudin‐5 and ZO‐1), which increased expression after the presence of hemodynamic‐like shear stress. Negligible cell injury was observed when the monolayers were cultured statically, conditioned to shear stress, and subjected to nonfluorescent dextran (70 kDa) transport studies. μHuB experienced size‐selective permeability of 10 and 70 kDa dextrans similar to other BBB models. However, with the ability to probe temporal and spatial evolution of solute distribution, μHuBs possess the ability to capture the true variability in permeability across a cellular monolayer over time and allow for evaluation of the full breadth of permeabilities that would otherwise be lost using traditional end‐point sampling techniques. Overall, the μHuB platform provides a simplified, easy‐to‐use model to further investigate the complexities of the human BBB in real‐time and can be readily adapted to incorporate additional cell types of the neurovascular unit and beyond.

Size, shape, and flexibility influence nanoparticle transport across brain endothelium under flow

“…As the nanoparticles investigated herein (100 nm and larger) are too large to utilize a paracellular route through the BBB, this was not viewed as a major drawback. μHuB chips were prepared as described previously . After flow conditioning, hCMEC/D3 cells retained their preconditioning morphology, resisting elongation (Figure b) and formed a complete monolayer (Figure c).…”

“…Figure a shows the device schematic. Devices were prepared as previously described . Briefly, devices were coated with 300 μg/ml human fibronectin for 1 hr, then perfused and primed with nitrogen gas to remove bubbles.…”

“…Development of dynamic microfluidic‐based in vitro systems that incorporate hemodynamic shear addresses several of these existing limitations . One such model particularly well suited to our investigations is the μHuB, a simplified and easy‐to‐use tool with real‐time imaging capabilities . The μHuB consists of a commercially available microfluidic chip scaffold and an immortalized cell line that incorporates physiologically relevant applied shear stresses and demonstrates size‐selective permeability to dextran tracers as well as expression of phenotypical tight junction markers.…”

Lab-On-A-Chip for the Development of Pro-/Anti-Angiogenic Nanomedicines to Treat Brain Diseases

“…The human-like perfusability, dynamic microenvironment, and the ability to carry out robust, rapid and reproducible assays in a controlled operational condition, with high throughput screening readouts, have made the above devices a super-tool to screen angiogenic drugs [41]. Some of the above devices were already evaluated for drug screening [32,34,36,38,40], and a few studied the effect of NPs [35,41] and NMs [39].Microfluidic technology has also been used to model brain vasculogenesis/angiogenesis [42][43][44][45][46], BBB [2,42,[47][48][49][50][51][52][53], brain tissues [54,55], and brain angiogenesis-related cellular events such as inflammation [47,50], cell migration [56], cell-cell interactions [57], etc., see Table 2. In addition, specific conditions, involving pathological-angiogenesis, such as brain tumors [46,[54][55][56]58], ischemic strokes [59], and neurodegenerative disorders including Alzheimer's disease (AD) [60], Parkinson's disease (PD) [61], and Huntington's disease (HD) [62], could also be created on-chip.In addition to this, LOCs have been developed for studying the biocompatibility, cellular uptake and transport of NMs [2,27], many of them focusing on brain angiogenesis [2,45,…”

“…Microfluidic technology has also been used to model brain vasculogenesis/angiogenesis [42][43][44][45][46], BBB [2,42,[47][48][49][50][51][52][53], brain tissues [54,55], and brain angiogenesis-related cellular events such as inflammation [47,50], cell migration [56], cell-cell interactions [57], etc., see Table 2. In addition, specific conditions, involving pathological-angiogenesis, such as brain tumors [46,[54][55][56]58], ischemic strokes [59], and neurodegenerative disorders including Alzheimer's disease (AD) [60], Parkinson's disease (PD) [61], and Huntington's disease (HD) [62], could also be created on-chip.…”