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NeuroVU: Real-time Sensing in Microfluidic Models of the Neurovascular Unit

Periodic Reporting for period 1 - NeuroVU (NeuroVU: Real-time Sensing in Microfluidic Models of the Neurovascular Unit)

Reporting period: 2018-06-27 to 2020-06-26

Brain-related disorders and diseases account for ~45 million disability-adjusted life-years (DALYs) lost, or around 15% of the total, in Europe alone. While this number is projected to rise, development of drugs for the central nervous system (CNS) has slowed down significantly over the past decades. Among the major challenges identified are the comparatively poor existing model systems (i.e. in-vitro cell-based models and rodents) and the resulting shortcomings in our understanding of brain biochemistry. Of particular interest for delivery of therapeutics to the CNS is the neurovascular unit (NVU), the interface between systemic circulation and the CNS.

The aim of my research project was to find a holistic solution for integration of biophysical and biochemical sensing capabilities, microfluidics, and neurovascular cells to provide a novel class of organ-on-a-chip (OoC) models of the neurovascular unit (NVU) with advanced real-time sensing capabilities, termed NeuroVU. These systems have the potential to provide unprecedented insight into neurovascular chemistry as well as accelerate pharmaceutical development. The research was carried out at the Kungliga Tekniska Högskolan (KTH) Stockholm in the Department of Micro- and Nanosystems (MST) under the supervision of Professor Anna Herland.
One part of the project was the development and characterization of novel fabrication approaches for OoCs. Current technology largely relies on silicones or thermoplastics, which are poorly suited to systems integration (particularly sensors, but also other components with disparate materials). The main Thrust was focused on off-stoichiometry thiol-ene-epoxy (OSTE+) which has very favorable properties for this type of OoC integration, though demonstrated applications had been very limited. I established that the material is compatible with highly sensitive cell culture such as human induced pluripotent stem cells (hiPSCs). I optimized its fabrication and assembly processes to be able to produce tens to hundreds of near-identical devices with relative ease. I moreover studied the ad- and absorption of small molecules, including fluorescent dyes and neuropsychopharmaca.

Another research direction arising from materials considerations was focused on adhesive tape. The standard OoC processes (as well as my OSTE+ process) are prohibitively expensive in terms of needed equipment and expertise for researchers outside of high-resource environments. I developed a process for fabricating a tissue barrier OoC based on simple stacking of cut-out double-sided tape and off-the-shelf parts, requiring only around one hundred euros initial equipment investment. I demonstrated biological functionality with a metabolic study of the effects of chili pepper capsaicinoids.

Using the OSTE+ approach, I demonstrated one of the first isogenic (i.e. from the same donor) hiPSC-based NVU OoC. By relying on isogenic hiPSCs, the NVU model can be highly specific not just to a disorder, but to an individual patient. With the integrated sensors, I was able to show unprecedented temporal resolution in monitoring barrier integrity. To demonstrate, I specifically focused on nitrosative stress and inflammation, as well as how the NVU can be protected by pharmaceutical intervention.

I furthermore pursued multiple research avenues to optimize or eliminate the plastic membranes that support cell growth in the aforementioned OoCs. In this realm, I showcased a new laser photoablation process to create ultra-thin, ultra-porous membranes from commercial plastic films. I characterized biomimetic hydrogel-based membranes created from bio-active silk proteins or nanofibrillar cellulose. Last but not least, I established a 3D hydrogel-based OoC with in-vivo-like tubular geometry that retains the monitoring capabilities of planar membrane-based approaches.

The research conducted within this project has been presented at a number of national and international conferences. Three peer-reviewed journal articles have already been published, with the most widely appealing featured in a university-wide press release. I moreover participated in Falling Walls Lab to garner more public attention. Dissemination activities will continue past the project end date, in particular with multiple journal manuscripts close to completion. Outreach opportunities are sadly somewhat curtailed this year, but will nonetheless continue to be pursued.
The ultra-low-cost tape-based OoC system has the potential to allow low-resource research facilities to enter a field currently dominated by only the highest-resource players. The developed OSTE+ fluidic platforms, on the other hand, open up a world of new sensor integration opportunities. Both approaches can significantly advance “3R” principles in biomedical research by enabling Replacement of animal in-vivo models with novel OoC approaches. True continuous monitoring capabilities integrated into OoCs represent a significant and highly innovative step beyond the state of the art for the field, allowing studies with unprecedented temporal resolution. Last but not least, the demonstrated isogenic hiPSC model of the NVU enables disorder- and even patient-specific studies, expanding NVU OoC application from simple barrier permeation tests into the realm of personalized medicine.