Multicellular Cell Seeding on a Chip: New Design and Optimization towards Commercialization

Exploring Endothelial Expansion on a Chip

Angiogenesis is the development of new blood vessels from the existing vasculature. Its malfunction leads to the development of cancers and cardiovascular diseases qualified by the WHO as a leading cause of death worldwide. A better understanding of mechanisms regulating physiological and pathological angiogenesis will potentially contribute to developing more effective treatments for those urgent issues. Therefore, the main goal of the following study was to design and manufacture an angiogenesis-on-a-chip microplatform, including cylindrical microvessels created by Viscous Finger Patterning (VFP) technique and seeded with HUVECs. While optimizing the VFP procedure, we have observed that lumen's diameter decreases with a diminution of the droplet's volume. The influence of Vascular Endothelial Growth Factor (VEGF) with a concentration of 5, 25, 50, and 100 ng/mL on the migration of HUVECs was assessed. VEGF's solution with concentrations varying from 5 to 50 ng/mL reveals high angiogenic potential. The spatial arrangement of cells and their morphology were visualized by fluorescence and confocal microscopy. Migration of HUVECs toward loaded angiogenic stimuli has been initiated after overnight incubation. This research is the basis for developing more complex vascularized multi-organ-on-a-chip microsystems that could potentially be used for drug screening.

A Protocol for Fabrication and on-Chip Cell Culture to Recreate PAH-Afflicted Pulmonary Artery on a Microfluidic Device

Pulmonary arterial hypertension (PAH) is a rare pulmonary vascular disease that affects people of all ethnic origins and age groups including newborns. In PAH, pulmonary arteries and arterioles undergo a series of pathological changes including remodeling of the entire pulmonary vasculatures and extracellular matrices, mis-localized growth of pulmonary arterial cells, and development of glomeruloid-like lesions called plexiform lesions. Traditionally, various animal and cellular models have been used to understand PAH pathophysiology, investigate sex-disparity in PAH and monitor therapeutic efficacy of PAH medications. However, traditional models can only partially capture various pathological features of PAH, and they are not adaptable to combinatorial study design for deciphering intricately intertwined complex cellular processes implicated in PAH pathogenesis. While many microfluidic chip-based models are currently available for major diseases, no such disease-on-a-device model is available for PAH, an under investigated disease. In the absence of any chip-based models of PAH, we recently proposed a five-channel polydimethylsiloxane (PDMS)-based microfluidic device that can emulate major pathological features of PAH. However, our proposed model can make a bigger impact on the PAH field only when the larger scientific community engaged in PAH research can fabricate the device and develop the model in their laboratory settings. With this goal in mind, in this study, we have described the detailed methodologies for fabrication and development of the PAH chip model including a thorough explanation of scientific principles for various steps for chip fabrication, a detailed list of reagents, tools and equipment along with their source and catalogue numbers, description of laboratory setup, and cautionary notes. Finally, we explained the methodologies for on-chip cell seeding and application of this model for studying PAH pathophysiology. We believe investigators with little or no training in microfluidic chip fabrication can fabricate this eminently novel PAH-on-a-chip model. As such, this study will have a far-reaching impact on understanding PAH pathophysiology, unravelling the biological mystery associated with sexual dimorphism in PAH, and developing PAH therapy based on patient sex and age.

Multilayer Soft Photolithography Fabrication of Microfluidic Devices Using a Custom-Built Wafer-Scale PDMS Slab Aligner and Cost-Efficient Equipment

We present a robust, low-cost fabrication method for implementation in multilayer soft photolithography to create a PDMS microfluidic chip with features possessing multiple height levels. This fabrication method requires neither a cleanroom facility nor an expensive UV exposure machine. The central part of the method stays on the alignment of numerous PDMS slabs on a wafer-scale instead of applying an alignment for a photomask positioned right above a prior exposure layer using a sophisticated mask aligner. We used a manual XYZR stage attached to a vacuum tweezer to manipulate the top PDMS slab. The bottom PDMS slab sat on a rotational stage to conveniently align with the top part. The movement of the two slabs was observed by a monocular scope with a coaxial light source. As an illustration of the potential of this system for fast and low-cost multilayer microfluidic device production, we demonstrate the microfabrication of a 3D microfluidic chaotic mixer. A discussion on another alternative method for the fabrication of multiple height levels is also presented, namely the micromilling approach.