How sugar could be used to extend the lifetime of artificial joints

Having manufactured pure sugars and syrups for nearly a century, we at Ragus have seen it all when it comes to sugar. However, the latest innovative application is new even to us.

A recent scientific discovery has found that sugar can be used for creating a long-lasting lubricative coating between surfaces. This research, undertaken by an international team of scientists, including Durham and York universities and Tsinghua University in China, could revolutionise the lifetime of joint-like mechanisms by reducing the damage caused by wear and tear. The researchers suggested that in the future, the sugar-containing polymer could even help repair artificial joint implants, demonstrating how the unique properties of sugar continue to amaze.

In any mechanism where there are moving parts – from joints in the human body, to the engines in machines – friction is created between the surfaces. Over time, this friction will inevitably wear down surfaces, reducing the mechanism’s efficiency and causing irreversible damage. To minimise this, a lubricant is needed. However, even with a protective layer, the constant use of the mechanism can still cause wear.

Until now, the materials used to create this protective, lubricative layer have required regular replacing, costing individuals time and money. So, how can sugar solve this problem?

The research initiative that began in 2018 looked to investigate how sugar polymers would interact with water molecules as a technique for longer-lasting lubrication between surfaces. The findings, which were published in the Chem – Cell Press at the end of last year, drew on the properties and past applications of sugar as inspiration.

Sugar is a humectant, meaning it binds water molecules easily and retains moisture. This makes it an ideal ingredient for materials designed to be slippery and protective. By using sugar in the protective coating, a layer of water is coaxed to the surface, creating a protective sheet between the interacting surfaces.

As well as being interested in the function of sugar to attract water and create a slippery protective layer, the researchers wanted to take it a step further. By investigating the properties of the sugar polymers, they found that the sugar-coating could be used to not only protect surfaces, but also to actively repair them.

To investigate this theory, the scientists focussed on a naturally occurring sugar compound. These sugar compounds are made up of chemical building blocks linked together to create a shape resembling a large ring – or a hoop – leaving a cavity in the centre. It’s this cavity that gives the sugar it’s potential.

‘There’s been decades of interest in these sugar rings,’  Dr McGonigal, the Associate Professor and senior writer of the paper explained, ‘because you can – theoretically – fit something inside that cavity.’

One popular use of sugar rings that already exists is in drug formulation.

‘It can help to have a pharmaceutical molecule like ibuprofen placed in the centre of the sugar ring. This way the drug is protected, and it can get into a person’s system faster.’

Another use of the sugar compounds is in air-freshener products, as the sugar ring can capture perfumed molecules and hold them inside its cavity. It was this history of sugar rings that inspired the researchers to investigate what else could be held inside the cavities.

For the purpose of this experiment, the scientists used modified titanium metals, testing whether the sugar rings would attach to the metals and hold them in place. Their findings showed that the sugar rings – in seeking something to fill the cavity – would self-assemble to the metal surface, latching on and creating a protective layer without the need for any human interference.

Every year in England and Wales, approximately 160,000 hip and knee replacement procedures are carried out. Replacements involve major surgery and can take up to two months to recover from, yet many patients are required to repeat the procedure more than once in their lifetime due to the materials wearing down over time.

The findings of the research team proposed that by using a polymer coating made up of sugar rings, it would work to lubricate the artificial joints, protecting the surfaces when they knock together. However, not only would the sugar-coating provide protection, it would also be capable of repairing itself over time as friction caused wear to the surfaces.

As the joints rub together and the coating wears down, the sugar ring’s capability to latch onto surfaces and hold them in its cavity would make it able to reattach when rubbed away, and so restore itself.

Dr McGonigal explained further: ‘we wanted the molecules to be able to latch onto the surface, and if they were knocked off to then come back and reattach without any human interference. Our body is able to repair wear to cartilage in the joints naturally, but in artificial joints this is not possible and so the material must be replaced. If you could have a replacement solution for what out body does, then you could repair the surface of the joint without having to take it out and put it back in. That could extend the lifetime potentially for as long as the person needed.’

Though the research focussed on the theoretical use of the sugar polymers in artificial joints, the list of potential uses is much longer. A lot of the joints in heavy machinery or car engines rely on protective coatings, and this sugar alternative could increase the lifetime of those.

As a natural humectant, sugar has a range of applications beyond flavour, including extending shelf-lives, retaining moisture to create textures, and stabilising the chemicals in products. The research undertaken by this team of scientists demonstrates another use of sugar beyond the food and beverage industry, highlighting the unique natural properties and varying possibilities of this inspiring product. Our team at Ragus Pure Sugars look forward to seeing what comes next.

Ragus has over 90 years’ experience manufacturing pure sugars and syrups for specialist applications. To learn more about our products, please contact our Customer Services Team. To see more sugar news and updates, continue browsing SUGARTALK and follow Ragus on LinkedIn.