Nov 3, 2015 | By Alec

While there are a number of very promising ongoing bioengineering projects that seek to use 3D printing to manufacture transplantable organs and tissue, most are facing the same hurdles. How do you get mixtures of polymers, silicone and a patient’s own cells to form miniscule and biocompatible vessels capable of transporting oxygen and nutrients? Well, a bioengineering team from Rice University and the University of Pennsylvania might have found a solution. As they explain in a recent paper, the team have used sugar glass and silicone to create a basic system of blood vessels that could lead the way to 3D printed transplantable organs and tissue.

This promising study was led by Jordan Miller, Assistant Professor of Bioengineering at Rice and Pavan Atluri, Assistant Professor of Surgery at the University of Pennsylvania. Other involved researchers include Renganaden Sooppan, Jason Han, Patrick Dinh, Ann Gaffey, Chantel Venkataraman, Alen Trubelja, George Hung and Pavan Atluri (Pennsylvania). As they explain in a report published in the journal Tissue Engineering Part C: Methods, they were able to creative a system of native blood vessels through which blood flowed normally when attached to a small animal model.

Essentially, this points to a solution to that big hurdle: ensuring that blood reaches every nook and cranny of an artificial organ or tissue implant. As professor Miller explains, tissue engineers typically rely on a patient’s own body to grow blood vessels into engineered tissue scaffolds. That process can take weeks, and isn’t compatible with artificial organs made outside the body – they’ll die from a lack of oxygen long before the blood vessels reach them. ‘We had a theory that maybe we shouldn’t be waiting. We wondered if there were a way to implant a 3-D printed construct where we could connect host arteries directly to the construct and get perfusion immediately. In this study, we are taking the first step toward applying an analogy from transplant surgery to 3D printed constructs we make in the lab,’ Miller explains.

But the issue is about more than blood vessels. It also requires a vessel inlet and outlet small enough to connect directly to existing arteries and veins. Using a technique pioneered by Miller in 2012, bioengineering graduate student Samantha Paulsen and research technician Anderson Ta developed an interesting proof of concept. The technique itself is inspired by sugar glass cages made by pastry chefs. 3D printing individual layers of sugar glass, they created a lattice of blood vessels. Once hardened, they used it as a mold for silicone gel. Upon curing, they were left with a small network of channels the size of a gummy bear. ‘They don’t yet look like the blood vessels found in organs, but they have some of the key features relevant for a transplant surgeon. We created a construct that has one inlet and one outlet, which are about 1 millimeter in diameter, and these main vessels branch into multiple smaller vessels, which are about 600 to 800 microns,’ Miller explains.

Importantly, the inlet/outlet creations enabled them to test the models, which the team did with the help of the Pennsylvania surgeons. Attaching the small proof of concept to an animal model’s artery, they found that they could pump blood through this set of channels. Using Doppler imaging technology, they were able to observe that the system even withstood the physiologic pressures of the blood, flowing perfectly and unobstructed for up to three hours.

While not exactly close to medical applications, this is definitely a breakthrough in this particular bioengineering field, Miller argues. ‘This study provides a first step toward developing a transplant model for tissue engineering where the surgeon can directly connect arteries to an engineered tissue. In the future we aim to utilize a biodegradable material that also contains live cells next to these perfusable vessels for direct transplantation and monitoring long term,’ he says.



Posted in 3D Printing Applications



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