Blood in their hands

Wounded soldiers on the battlefield and victims of natural disasters may be saved in future by 'plastic blood', recently developed by researchers at Sheffield University.

The lightweight polymer would be manufactured and stored in dehydrated form so medical teams would only need to add water to create O negative, the universally-transfusible blood type.

The plastic promises to be a fast, life-saving answer to victims in critical need of blood. It will also circumvent problems associated with human-donated blood, which can pass on diseases such as hepatitis C or HIV.

The artificial blood is made of plastic molecules that hold an iron atom at their core, in a similar manner to haemoglobin, so they can bind oxygen and transport it around the body.

Lance Twyman, lead researcher at Sheffield, created the molecules in the university's laboratories by using glycidol, a monomer, to polymerise an iron-cored porphyrin into a hyper-branched, tree-like structure. He has been working on the project for the last five years but said the quest to create 'artificial blood' has been going on for many years.

Twyman said earlier attempts were unsuccessful because researchers tried to use the porphyrin itself. 'The problem with that is porphyrins try to aggregate when they are in water, and while [previous researchers] had some tricks to try to stop that, they were working with organic solvents,' he said.

'It wasn't until recently the scientific community developed this new type of hyper-branching polymer. So instead of polymerising like a normal polymer in a straight line, these new ones polymerise in three directions, like a tree growing. So if we start the polymerisation with one of these porphyrins, we can ensure that the porphyrin is at the centre of a globular polymer that isn't going to change its shape very much. What we have is a polymer that really does mimic the shape and size of haemoglobin.'

While some might think that artificial blood would look different from real blood, Twyman describes the polymer as a blood-red paste with the consistency of honey. 'The red colour comes from the porphyrin, which is also what gives blood its red colour,' he said.

It might sound risky to inject plastic into a person's veins, even to save their life. However, Twyman points out that porphyrins are natural, and the polymer component would be ignored by the body's immune system.

While the Sheffield researchers need to tweak their polymer for another few months before biological testing begins, they say laboratory tests using spectroscopy have been successful. 'There will have to be toxicology tests done before animal or human studies,' said Twyman, adding that if the tests show positive results, artificial blood could be used in critical situations outside the hospital in seven years' time.

That does not mean artificial blood will be used in the same way as real blood. 'Ideally, it would be a true replacement for blood, but that's far too complicated,' he said. 'It is likely to be used as an alternative to plasma, which is given when people are bleeding to death. It gives the heart something to pump but it doesn't do anything in terms of oxygen binding.'

Twyman said the goal is to use it as a 'top-up for your own blood, not to replace it.' He said: 'It would be suitable for all trauma situations such as roadside accidents or battlefields. It could be used in an earthquake scenario with many casualties unconscious and bleeding to death. You won't have time to find out what blood group they are so we would be able to give them this.'

Even if the biological testing fails Twyman, who has a PhD in polymer chemistry, said his work could be used in a multitude of hyperbranch polymer applications, ranging from the ink to the car industries. 'The fact that it's a new way of thinking about branch polymers means it might not be this product or this molecule being used,' he said, 'but a molecule that is similar or based on this might be.'