Medical & Dental

CU Boulder researchers develop 3D printing technique to create hardened artificial blood vessels

Researchers from the University of Colorado Boulder (CU Boulder) have developed a 3D printing method using controlled oxygen inhibition to imitate the highly structured, pliable geometry of blood vessels.

“The idea was to add independent mechanical properties to 3D structures that can mimic the body’s natural tissue,” said Xiaobo Yin, an Associate Professor in CU Boulder’s Department of Mechanical Engineering and the senior author of the study.

“This technology allows us to create microstructures that can be customized for disease models.”

Hardening 3D printed blood vessels

According to the research, engineering a solution for hardened blood vessels associated with cardiovascular disease and viable artery and tissue replacement has been “historically proven challenging”. Using a 3D printer built with parts purchased from eBay at a total cost of $500, the researchers developed a stereolithography 3D printing method to manufacture microscopic structures.

This method integrates an oxygen inhibition layer between a cured polymer structure to physically limit the curing thickness during the additive manufacturing process.“Oxygen is usually a bad thing in that it causes incomplete curing,” said Yonghui Ding, a Postdoctoral researcher in Mechanical Engineering and the lead author of the study. “We utilize a layer that allows a fixed rate of oxygen permeation.”

“By keeping tight control over oxygen migration and its subsequent light exposure, the researchers have the freedom to control which areas of an object are solidified to be harder or softer—all while keeping the overall geometry the same.”

a) A Schematic set-up of digital projection stereolithographic 3D printing system where hydrogel precursor solution is cured layer-by-layer through UV exposure. b) Schematic of oxygen inhibition-assisted printing, in which the curing zone is physically limited between the cured region and the oxygen inhibition layer. c) Depth profile of double bond conversion rate
under different UV exposure dosages. Image via CU Boulder.

Mimicking the diseased blood vessels

Testing their concept, the researchers printed three versions of structure featuring a top beam supported by two rods. The structures were identical in shape, size, and materials, but had been printed with three variations in rod rigidity: soft/soft, hard/soft and hard/hard. Following this, the team found that the harder rods supported the top beam while the softer rods allowed it to fully or partially collapse.

The researchers also printed a small Chinese warrior figure, with hard outer layers and soft interior layers, which gave the warrior varied textures. CU Boulder believes that this method is “opening a new avenue towards 3D in vitro tissue fabrication.” This research is also said to accelerate more personalized treatments for those suffering from hypertension and vascular diseases.

“We were able to create this structure to mimic the diseased blood vessel. We can use it to test drugs before they go to clinical trial,” explained Ding. “This is a profound development and an encouraging first step toward our goal of creating structures that function like a healthy cell should function.”

The researchers are now working on depositing cells during the 3D printing process to make a living artery.

The research paper “Orthogonal programming of heterogeneous micro-mechano-environments and geometries in three-dimensional bio-stereolithography” is co-authored by Hang Yin, Yonghui Ding, Yao Zhai, Wei Tan, and Xiaobo Yin.

a) stiff/stiff, b) soft/stiff, and c) soft/soft structures. d, e, and f show the 3D printed warrior model with stiff body with a soft heart inside. Image via CU Boulder.
a) stiff/stiff, b) soft/stiff, and c) soft/soft structures. d, e, and f show the 3D printed warrior model with a stiff body and a soft heart inside. Image via CU Boulder.

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Featured image shows an illustration of arteries. Image via CU Boulder.