A new biodegradable gel has been developed by the University of Manchester to repair damage caused by a heart attack.
Experts at the university, backed by the British Heart Foundation (BHF), created the substance, which can be injected directly into the beating heart.
The gel - made of amino acids called peptides, the building blocks of proteins - works as a scaffold for injected cells to grow new tissue.
It behaves like a liquid when it is under stress as the peptides disassemble, and then work to reassemble, making it a solid.
This holds the cells in place as they graft onto the heart.
In the past, when cells have been injected into the heart to reduce the risk of heart failure, only 1% have stayed in place and survived.
For the results to be successful, a good blood supply is vital for the injected cells to be able to develop into a new tissue.
To prove that the technology could work, researchers showed the gel can support growth of normal heart muscle tissue.
When they added human cells that had been reprogrammed to become heart muscle cells into the gel, they were able to grow them in a dish for three weeks and the cells started to spontaneously beat.
They also tested the gel on healthy mice.
They injected a fluorescent tag with the gel into their hearts, and the results revealed that the gel stayed on the hearts for two weeks.
Echocardiograms (ultrasounds of the heart) and electrocardiograms (ECGs, which measure the electrical activity of the heart) on the mice confirmed the safety of the gel.
To gain more knowledge, researchers plan to test the gel after mice have a heart attack to see if they develop new muscle tissue.
The study has being presented at the British Cardiovascular Society Conference in Manchester.
Professor James Leiper, associate medical director at the British Heart Foundation, said: "We've come so far in our ability to treat heart attacks and today more people than ever survive.
"However, this also means that more people are surviving with damaged hearts and are at risk of developing heart failure.
"This new injectable technology harnesses the natural properties of peptides to potentially solve one of the problems that has hindered this type of therapy for years.
"If the benefits are replicated in further research and then in patients, these gels could become a significant component of future treatments to repair the damage caused by heart attacks."
Katharine King, from the University of Manchester, who led the research, said: "The heart has a very limited ability to repair any damage it sustains.
"Our research has been looking for ways to overcome this so we can keep the heart in a healthier place for longer.
"While it's still early days, the potential this new technology has in helping to repair failing hearts after a heart attack is huge.
"We're confident that this gel will be an effective option for future cell-based therapies to help the damaged heart to regenerate."