Associate Professor Daniel Heath, Professor Andrea O’Connor and Hazem Alkazemi, writing for Pursuit - a University of Melbourne medical research site:
First we needed to create the shape, a kind of framework on which to grow the blood vessel layers. We did this by electrospinning a layer of polymer fibres onto a mandrel, which provides the tubular shape for the blood vessel graft.
Electrospinning is a technique that uses an electrical voltage to draw a polymer stream into thin fibres that mimic the protein structure of our native tissue, a bit like spinning wool onto a bobbin at the nano-scale.
However, this process results in fibres that are randomly oriented, when we need fibres aligned along the length, or axis, of the tube to promote axial alignment of the endothelial cells.
To align these fibres, we developed a simple freezing technique.
By placing the electrospun tube into a rigid mold partially filled with water and freezing it, we caused ice crystals to grow along the axis, which pushed the fibres into alignment.
We then grew endothelial cells on the tube to create the inner layer of the vessel – the endothelium. The cells spontaneously align with the fibres, generating a continuous, aligned endothelial cell layer like we see in native blood vessels.
This layer also provides appropriate mechanical properties, enables the graft to be sutured to native blood vessels and prevents rupture of the graft.
Next, we cast a soft hydrogel layer around the electrospun fibres. This hydrogel layer prevents leakage from our graft and also acts as a scaffold for smooth muscle cells.
We know that cells are very sensitive to the stiffness of their surroundings so we trialled hydrogels of varying stiffness.
Surprisingly, we observed that the softer gels allowed the vascular smooth muscle cells to rapidly and spontaneously align in a 3D ring structure, mimicking what is found in native blood vessels.
Well - I can look forward to getting all of my internal plumbing replaced for my 65th birthday…