Harvard Bioengineers Print Custom Blood Vessel Grafts in Minutes

The problem with small vessels

When trauma or vascular disease damages a blood vessel, surgeons often have to replace the injured section. For the smallest vessels, the options are grim. Anything under about 6 millimeters across has no clinically approved artificial implant. Surgeons fall back on taking a graft from elsewhere in the patient's body, an extra invasive step that still may not match the size or shape of the vessel they are trying to fix.

A printer that spins fibers

Researchers in Kit Parker's lab at Harvard's John A. Paulson School of Engineering and Applied Sciences have a different idea. They use a technique called Focused Rotary Jet Spinning. The machine flings liquid polymer through high speed air streams, laying ultra thin fibers onto a rotating mandrel. The fibers stack into a tube that looks and behaves a lot like a real blood vessel.

The pitch is speed. The team showed it can build these grafts in minutes, with control over diameter and wall thickness. That opens the door to making a graft for one specific injury, in one operating room, while the patient is on the table.

Why this matters in the OR

The researchers call it intraoperative manufacturing. In a car crash or on a battlefield, a torn artery is a clock. High blood pressure means fast blood loss, and a graft sized on the spot could save a limb or an organ. The same approach could help children born with heart defects, where surgeries are already highly individual and complex.

What the graft is made of

The grafts use a synthetic copolymer of polylactic acid and polycaprolactone. As the material spins, it forms nano and microscale fibers that mimic the body's own extracellular matrix. Once implanted, the tube holds up against blood pressure. Over time it breaks down while the patient's own cells rebuild the vessel wall, with the goal of fast inner lining growth to keep blood flowing smoothly and limit clotting.

What comes next

The work, led by former Parker lab PhD student Michael Peters, landed on the cover of Advanced Materials. So far the team has built centimeter scale grafts for small animal surgery with collaborators in Zurich. The next step is larger animal models and longer tests at different pressures and flow rates. Parker imagines a day when FDA grade manufacturing happens inside the hospital, much like dentists already print crowns chairside.

The Harvard Office of Technology Development has filed intellectual property and is looking at commercialization. For now, the result is a concrete demonstration that vascular implants do not have to come from a shelf.