Dr Pete Twigg examines
some bone prepared to trial
the hydrogel

A hydrogel with a 'unique' crosslinker could improve cartilage repair. This will enhance the lives of people suffering from medical joint problems such as osteoarthritis.

The research from the University of Bradford, UK, and its spin-out company Advanced Gel Technology Sciences Ltd (AGT),exploits the high water content, inertness and biocompatibility of hydrogels, as well as their chondroconductivity, which allows cells to live in or on the gel.

‘The difficulty in matching the mechanical behaviour of cartilage is in achieving low friction and high wear resistance in a material with such a low modulus (of the order of one megapascal),’ says Dr Pete Twigg, Senior Lecturer in Medical Engineering at the University of Bradford.

Advanced Gel Technology has developed a proprietary crosslinker for the polymeric material that it says provides improved control over the hydrogel’s structure and its properties.

Twigg says, ‘It is more biomimetic than previous approaches. That should mean the hydrogel lasts longer in the joint and should prevent damage to the cartilage counterface. The compressive stiffness, as well as its friction and wear properties, are optimised for the sliding wear conditions of the articular surface of the joints’.

Because cartilage is mainly an extracellular matrix, natural repair is poor. Accumulated cartilage wear leads to osteoarthritis, which is accelerated by localised damage, such as sports injuries.

Twigg says, ‘Osteoarthritis can be successfully treated through joint replacement, but these implants have a limited lifetime, and so surgeons are reluctant to use them in younger patients. This means there is usually a long period of managing osteoarthritis through pain relief’.

He adds, ‘There is enormous demand for conservative treatments for localised osteoarthritis that can be used earlier in life and will not compromise future joint replacement’.

Autologous chondrocyte implantation involves culturing cartilage cells in the laboratory and injecting them into the afflicted area. However, ‘this process is costly, and the cartilage produced is of poor quality,’ says Twigg.

The new repair gel could overcome this. The current approach is to insert cylindrical plugs of the hydrogel into the tear through minimal invasive surgery to prevent bones rubbing against each other. Eventually, the team aims to inject the polymer solution and crosslinker into the damaged area so that it cures in situ.

‘This would provide a significant stop gap before joint replacement. For others it would be the only treatment required,’ adds Twigg.

Clinical trials are yet to be undertaken, and AGT eventually hopes to license out the technology. ‘We are also looking at tissue engineering approaches,’ says Twigg.