BBB-on-a-Chip: Modeling Functional Human Blood-Brain Barrier by Mimicking 3D Brain Angiogenesis Using Microfluidic Chip

Microphysiological Blood-Brain Barrier Systems for Disease Modeling and Drug Development

The blood-brain barrier (BBB) is a highly controlled microenvironment that regulates the interactions between cerebral blood and brain tissue. Due to its selectivity, many therapeutics targeting various neurological disorders are not able to penetrate into brain tissue. Pre-clinical studies using animals and other in vitro platforms have not shown the ability to fully replicate the human BBB leading to the failure of a majority of therapeutics in clinical trials. However, recent innovations in vitro and ex vivo modeling called organs-on-chips have shown the potential to create more accurate disease models for improved drug development. These microfluidic platforms induce physiological stressors on cultured cells and are able to generate more physiologically accurate BBBs compared to previous in vitro models. In this review, different approaches to create BBBs-on-chips are explored alongside their application in modeling various neurological disorders and potential therapeutic efficacy. Additionally, organs-on-chips use in BBB drug delivery studies is discussed, and advances in linking brain organs-on-chips onto multiorgan platforms to mimic organ crosstalk are reviewed.

The Art of Building Living Tissues: Exploring the Frontiers of Biofabrication with 3D Bioprinting

The scope of three-dimensional printing is expanding rapidly, with innovative approaches resulting in the evolution of state-of-the-art 3D bioprinting (3DbioP) techniques for solving issues in bioengineering and biopharmaceutical research. The methods and tools in 3DbioP emphasize the extrusion process, bioink formulation, and stability of the bioprinted scaffold. Thus, 3DbioP technology augments 3DP in the biological world by providing technical support to regenerative therapy, drug delivery, bioengineering of prosthetics, and drug kinetics research. Besides the above, drug delivery and dosage control have been achieved using 3D bioprinted microcarriers and capsules. Developing a stable, biocompatible, and versatile bioink is a primary requisite in biofabrication. The 3DbioP research is breaking the technical barriers at a breakneck speed. Numerous techniques and biomaterial advancements have helped to overcome current 3DbioP issues related to printability, stability, and bioink formulation. Therefore, this Review aims to provide an insight into the technical challenges of bioprinting, novel biomaterials for bioink formulation, and recently developed 3D bioprinting methods driving future applications in biofabrication research.

Human blood-labyrinth barrier on a chip: a unique in vitro tool for investigation of BLB properties

Hearing loss is one of the leading causes of disability worldwide, usually as a result of hair cell damage in the inner ear due to aging, acoustic trauma, or exposure to antibiotics or chemotherapy. No drug therapies can protect or restore hearing and current in vitro and animal models used in drug discovery have a very low success rate, mostly due to major differences in anatomy and accessibility of the inner ear environment between species. The blood-labyrinth barrier (BLB) in the stria vascularis is a highly specialized capillary network that controls exchanges between the blood and interstitial space in the cochlea. The BLB is critical for normal hearing, functioning as a physical, transport, and metabolic barrier. To address its complexity and accessibility, we created the first micro-engineered human model of BLB on a chip using autogenous progenitor cells from adult temporal bones. We successfully isolated the BLB from post-mortem human tissue and established an endothelial cell and pericyte culture system on a BLB chip. Using biocompatible materials, we fabricated sustainable two chamber chips. We validated the size-dependent permeability limits of our BLB model by measuring the permeability to daptomycin (molecular weight 1.6 kDa) and midazolam (molecular weight 325.78 Da). Daptomycin did not pass through the BLB layer, whereas midazolam readily passed through the BLB in our system. Thus, our BLB-chip mimicked the integrity and permeability of human stria vascularis capillaries. This represents a major step towards establishing a reliable model for the development of hearing loss treatments.