Researchers 3D Print Microfluidic Blood Vessel Model to Study Disease-Causing Blood Clots

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We’ve seen 3D printed blood vessels before – even an entire functioning network of them that was surviving in mice – but researchers in the Netherlands who are working with blood vessels and 3D printing technology are focused on something a little different. The team, consisting of scientists from the University of Twente and Utrecht University, is using 3D printing techniques to replicate the interaction between the flow of blood and blood vessel walls, in order to reproduce and study blood clots.

Blood clots in a person’s artery, or arterial thrombosis, can be fatal, and are one of the top causes of heart attacks and strokes, which result in over 14 million deaths around the world each year. 3D printing has been used in the past to help doctors identify the types of plaque that cause heart attacks, but by mimicking blood flow in the artery walls, this research team hopes to duplicate both diseased and healthy blood vessels in vitro for the purpose of controlled studies.

3D printed microfluidic blood vessel chip, with and without stenotic defect.

The researchers developed a more anatomically correct, microfluidic blood vessel model, using layered stacks of computed tomography angiography (CTA) data and stereolithography, that mimics a blood clot forming due to stenosis defects (blood vessel narrowing).

The team published a paper on this important research, titled “Mimicking arterial thrombosis in a 3D-printed microfluidic in vitro vascular model based on computed tomography angiography data,” in Lab on a Chip; authors include Pedro F. Costa, Hugo J. Albers, John E.A. Linssen, Heleen H.T. Middelkamp, Linda van der Hout, Robert Passier, Albert van den Berg, Jos Malda, and Andries D. van der Meer.

Microscopy images of a 3D model incorporating two curves of approximately 80°, measured from the centre of curvature. (a) Close up of a print encapsulated in PDMS. (b) Close up of a cast PDMS chip after successful mould removal. Scale bar, 400 µm

The study’s abstract explains:

Microfluidic chip-based vascular models allow controlled in vitro studies of the interaction between vessel wall and blood in thrombosis, but until now, they could not fully recapitulate the 3D geometry and blood flow patterns of real-life healthy or diseased arteries. Here we present a method for fabricating microfluidic chips containing miniaturized vascular structures that closely mimic architectures found in both healthy and stenotic blood vessels. By applying stereolithography (SLA) 3D printing of computed tomography angiography (CTA) data, 3D vessel constructs were produced with diameters of 400 μm, and resolution as low as 25 μm. The 3D-printed templates in turn were used as moulds for polydimethylsiloxane (PDMS)-based soft lithography to create microfluidic chips containing miniaturized replicates of in vivo vessel geometries. By applying computational fluid dynamics (CFD) modeling a correlation in terms of flow fields and local wall shear rate was found between the original and miniaturized artery. The walls of the microfluidic chips were coated with human umbilical vein endothelial cells (HUVECs) which formed a confluent monolayer as confirmed by confocal fluorescence microscopy. The endothelialised microfluidic devices, with healthy and stenotic geometries, were perfused with human whole blood with fluorescently labeled platelets at physiologically relevant shear rates. After 15 minutes of perfusion the healthy geometries showed no sign of thrombosis, while the stenotic geometries did induce thrombosis at and downstream of the stenotic area.”

Thrombosis-on-a-chip fabrication process. (a) The 3D model as seen directly after printing. (b) The blue support struts were removed with a scalpel; small “pinches” were sufficient to detach the struts due to their small diameter. PDMS was then cast into the mould-box (red dotted line). (c) PDMS was cured overnight at 60 °C, resulting in a 4mm chip thickness. After curing, the PDMS was separated from the mould box by cutting the box at the edges with a scalpel and breaking it open. The removal of the 3D printed model vessel was conducted in two steps using forceps, and without the need for bending the PDMS chip during removal. (d) First, the model was gently pulled at the outlet side, where it broke at the thinnest part of the stenosis or at the heel of the outlet in case of the healthy channels. (e) Afterwards, the rest of the 3D printed construct was removed from the inlet side. (f) Full 3D PDMS microfluidic chip.

The researchers 3D printed a mold of the blood vessel structure, and poured in a mixture of a crosslinking agent and PDMS, then cured the mold to make the vessel’s channel. Then they lined the channel with endothelial cells and perfusing (passing) blood, which was flowing at normal arterial shear rates. This allowed them to set up the ideal circumstances to form a blood clot. Due to the geometry of the 3D printed model, it offers more clinical relevance to researchers than the usual in vitro models with square walls, because it “achieves an even distribution of shear stress across the vessel.”

The paper reads, “Overall, the novel methodology reported here, overcomes important design limitations found in typical 2D wafer-based soft lithography microfabrication techniques and shows great potential for controlled studies of the role of 3D vessel geometries and blood flow patterns in arterial thrombosis.”

The research team believes that patient CTA data could allow them to go even further in their work, and develop patient-specific, 3D printed blood vessel models. In addition, the technique they used to gain resolution and control of blood vessels may offer a better model alternative for diseases like vascular dementia, and could even be used to develop a “fully stratified approach” to the research of vascular diseases, which may mean that less animals would be used in these types of studies. Discuss in the 3D Printed Blood Vessels forum at 3DPB.com.

[Source: Medical Physics Web / Images: researchers via Lab on a Chip]

 

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