Joint lubrication is crucial for the relief of those suffering with arthritis. However, the lubricants currently used break down in the body and lose their effectiveness. But now, researchers at Boston University believe that they have developed a synthetic polymer that does not break down and so will be a more effective lubricant. This could have considerable significance for those facing the prospect of knee replacement surgery.
According to research team member Mark Grinstaff, the team has been working on ways to increase the molecular weight of a polymer methyl 5-oxanorbomene-2-carboxylate to create a large molecular weight polyanion, sodium poly (7-oxanorbomene-2-carboxylate) by using a ring-opening metathesis polymerisation process. This has allowed them to create longer chains and increase the polymer’s molecular weight to up to 2.5 million.
At these molecular weights, the rheological properties (flow characteristics) change and the team found that when dissolved in water their polymer became slippery to the touch, leading them to consider the possibility that it might be useful as a joint lubricant for those with osteoarthritis.
As Grinstaff explains, the polymer has two advantages over current lubricants:
- Because of its higher molecular weight, it will remain in the joint longer as opposed to diffusing through the cartilage.
- Unlike current products that are based on cross-linked hyaluronic acid solutions, it has a carbohydrate skeleton and so does not get broken down by the enzymes in the synovial fluid, which also helps keep it in the joint longer.
His team plans to develop the polymer so that it can be injected into the knee to reduce pain and delay the need for total knee replacement surgery.
Imperial College’s Philippa Cann has expressed interest in the approach, but remains cautious. She points out that the polymer has only been tested on cartilage from cadavers, which is entirely different from injecting it into a joint that already contains synovial fluid and might already exhibit cartilage damage. Tests under more physiologically relevant conditions are therefore required to help understand how the polymer will react to other substances present in the joint