3D printed vascular grafts advancing cardiovascular surgery

Cardiovascular diseases, such as blocked arteries, are a leading cause of death globally. Surgeons often replace or bypass damaged or blocked arteries using grafts, which can be made from veins taken from the patient's own body or synthetic materials. However, these options can have complications, such as poor compatibility with the body – the patient's own veins might not always be the right size or may fail over time – while synthetic grafts often lead to issues like infections or poor blood flow through the graft.

To overcome these issues, the researchers developed a two-step method for creating vascular grafts using a combination of advanced 3D printing, specifically extrusion printing, and a technique called electrospinning.

Extrusion Printing

The process begins with extrusion printing, where a gel-like substance known as GelMA (gelatin methacryloyl) – a modified form of gelatin – is layered to form the basic structure of the graft.

This material is chosen for its biocompatibility, meaning it is safe for use in the human body and supports the survival and growth of cells.

After the GelMA structure is printed, the next step involves electrospinning.

Electrospinning

Electrospinning adds an outer layer of extremely fine fibres around the GelMA structure. These fibres are made from a blend of polymers, including polycaprolactone (PCL) and poly(L-lactide-co-𝜖-caprolactone) (PLCL). These materials are plastic-like and can be adjusted in composition to alter the mechanical properties of the graft, such as its strength and elasticity. The researchers found that these fibre-reinforced grafts are not only strong but also flexible, closely mimicking the natural properties of human arteries.

By varying the composition of the polymers in the fibres, they could create grafts that were more or less elastic, depending on the type of artery they were intended to replace. The strength of the grafts, reinforced by 100% PCL or a mix of 75% PCL and 25% PLCL, was comparable to that of native arteries, with burst pressures exceeding those of small-diameter arteries.

Human compatibility

Another key finding from the study was that the materials used in these grafts are biocompatible, meaning they are safe for use in the human body and support the growth of cells that naturally line blood vessels, helping the graft to integrate with the body. This biocompatibility is important because it helps the graft integrate better with the patient’s existing blood vessels, reducing the likelihood of complications such as blood clots or graft failure. Moreover, the GelMA material provides a bioactive surface that encourages the survival and proliferation of endothelial cells, which are essential for the proper functioning of blood vessels.

The 3D printing technique used in this research also allows for the customisation of grafts to meet the specific needs of individual patients. This means that grafts can be tailored in size and mechanical properties to suit different patients, potentially leading to better outcomes in surgeries.

The resulting grafts are flexible enough to mimic the natural elasticity of human arteries and can be produced in a range of diameters. Preclinical testing showed that the grafts exhibited good mechanical strength, with properties closely aligned with those of natural vessels, indicating they could be very suitable for cardiovascular surgeries. However, further research, including clinical trials, is necessary to confirm their effectiveness and safety in patients.

Looking to the future, the team will research the use of the blood vessels in animals, in collaboration with the University of Edinburgh’s Roslin Institute, followed by trials in humans. This study presents a promising new method for creating vascular grafts that could improve the success rates of surgeries for cardiovascular diseases. The grafts are designed to closely mimic the properties of natural arteries, making them more compatible with the human body and potentially leading to fewer complications.

In essence, this research offers a step forward in developing better, more reliable replacements for damaged blood vessels, which could benefit many patients undergoing heart and vascular surgeries.