Brian Roberts is a man who is running out of options, but doctors hope a bio-engineering development could one day help people in his situation.

Key points: Many patients like Mr Roberts are facing limb amputation after their bodies reject stents or grafts

Many patients like Mr Roberts are facing limb amputation after their bodies reject stents or grafts Researchers develop a liquid "cloak" using a naturally occurring human molecule to trick the body into accepting the implant

Researchers develop a liquid "cloak" using a naturally occurring human molecule to trick the body into accepting the implant The discovery will not be tested on humans for at least another four to seven years

His scars show the price he has paid for his love of motorbikes.

The day before Mr Roberts' 20th birthday, his motorbike slid on spilt diesel and he crashed head-on with a cement truck.

In the decades since the 1974 accident, his body has rejected a graft and stent, and doctors may be forced to amputate his leg.

Researchers are now on the cusp of discovering why some bodies reject medical devices, and what can be done to prevent it from happening — including developing a liquid that appears to trick the body into accepting an implant.

"I was very lucky. I almost bled to death," Mr Roberts said.

The bike's handlebars pierced his thigh and struck Mr Roberts' femoral artery.

Brian Roberts has compartment syndrome after complications from a motor bike accident. ( ABC News: Brendan Esposito )

"There was a mortician going one way and a doctor going the other and they tied the artery off," he said.

"I like to think that one of them knew that one of them was going to get more work from me."

The accident set off a litany of medical problems that he is still dealing with today at the age of 64.

Surgeons took a graft from the main vein from his right thigh, to repair the one on his left.

The 250cc motor bike after Mr Roberts' crash in 1974. ( ABC News: Brendan Esposito )

While it worked for many decades, he didn't realise over time the grafts had been rejected by his body, something that should have been picked up by regular medical checks.

About three years ago, the graft was replaced by a metal stent, which also failed after 18 months.

During that time, while blood flow to his lower leg was minimal, he developed a serious staph infection and his leg started to discolour and die.

"There is nothing in your body that says this stent is failing," Mr Roberts said.

"You don't know it's failed until you suffer the consequences of the failure."

His lower leg was swollen to the size of his thigh, becoming red and inflamed. Doctors did everything they could to control the infection.

Brian Roberts' body has rejected stents and grafts. ( ABC News: Brendan Esposito )

Six months ago doctors took a vein from his arm and grafted it in his leg in a last-ditch effort to repair his vein damaged in that 1974 crash.

If that fails, Mr Roberts is out of options and doctors will have to amputate his leg.

New liquid tricks body into accepting implant

Dr Richard Tan from the Heart Research Institute (HRI) is the brains behind a new bio-engineered liquid, designed to trick the body into accepting an implant.

At 34, he is considered one of the leaders in his field of research.

Dr Richard Tan's research is showing promising results. ( ABC News: Brendan Esposito )

Early lab trials show promising results, and while human trials are still some way off, Dr Tan hopes they are just as successful.

"We have developed a coating for these devices that can essentially tell our body's inflammatory system to turn off, making these grafts more acceptable to the body," he said.

He said the liquid acts like a cloak, resulting in a striking improvement in the lifespan and effectiveness of medical implants.

"We think if you can tell the body to accept an implant better, it will increase how long they last and how effective they are," said Professor Steve Wise, from HRI.

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Every year up to 20,000 Australians need a coronary bypass to restore normal blood flow to an obstructed artery.

Even more people are hospitalised each year for peripheral artery disease.

For those patients, their best treatment option is to get a small bypass graft for the heart or leg, using arteries from their own body.

But up to a third of patients cannot use their own veins because they have been damaged.

New synthetic vascular grafts made from PCL at the Heart Research Institute in Sydney. ( ABC News: Brendan Esposito )

Those patients need synthetic vein alternatives, which often fail within a year if they are placed in the heart, or within three years if used in the legs.

The new liquid is made from a naturally occurring molecule found in the human body.

"The coating we applied to these grafts... prevents the foreign-body response to the implant, which makes it last a lot longer by switching off the body's immune system and preventing rejection of that graft," Dr Tan said.

At the moment, researchers are focusing their attention on grafts used in coronary bypass surgery.

A stainless steel stent is soaked in a solution of human cytokine. ( ABC News: Brendan Esposito )

"But we believe this can be applied to many other grafting applications throughout the body. And more broadly, just be applied to medical devices that get implanted and need to perform for long periods of time," he said.

The discovery will not be tested on humans for at least another four to seven years.

But if the research continues to be successful, the discovery of this new bio-engineered material has the potential to impact millions of people who need implants to stay alive each year.

For Mr Roberts, trials on the new liquid can't come soon enough.

"It would be wonderful given my history," he said.

The solution of human cytokine is called interleukin-4. ( ABC News: Brendan Esposito )

Mr Roberts has the early stages of heart disease and is likely to require cardiac stents to keep his arteries open.

Despite the unknown, and years of pain, struggles, surgeries and limited mobility, his positivity has remained intact.

"Given my history of them failing it would be wonderful if there was something to stop them failing," he said.