Design, Naturally: Sharkskin V Superbugs

By Anwen Bowers

Antimicrobial resistance is one of the biggest challenges faced by the healthcare industry. The evolution of superbugs such as MRSA is evidence that the arms race between antibiotics and bacteria is not a sustainable strategy for preventing infection and keeping patients healthy. Bacteria are able to make infinite changes to their DNA, but there isn’t an infinite supply of new drugs available to target them. Scientists looking for alternative methods to tackle the spread of disease causing bacteria have turned to the natural world for inspiration.

Bacteria in hospitals spread through contact. If a person touches a surface that hosts bacteria, they can pass it along next time they touch a piece of equipment, or a patient. So could making surfaces inherently resistant to bacteria be an effective way of stopping the transfer and spreading of disease?

Traditional approaches to keeping surfaces sterile involve using some sort chemical agent, for example treating socks with silver to keep smelly feet at bay (equally effective against vampires). The disadvantage of chemical treatment is that protection is short lived, and needs constant renewal. Research suggests that silver nanoparticles in socks last not much longer than a few washes, as the silver is rinsed out into the environment where it becomes a poisonous threat to wildlife.

In a paradigm shift in strategy, scientists have proposed a new mechanical approach to keeping surfaces clean. Taking inspiration from the sea, they want to develop a texture that prevents bacteria from spreading by discouraging microbes from settling in the first place.

Place almost anything underwater and it won’t be long before a thin film of green slimy phytoplankton will start to settle. This plankton is the trigger for a chain reaction of settlement, as larvae of adhesive animals such as anemones and barnacles will soon follow. This has long been a problem for the shipping industry as fouling like this on ship’s hulls creates a huge amount of drag, slowing down the vessel and adding fuel costs. Even whales, despite their constant movement, will succumb to the nuisance of barnacles and parasites.

But scientists observed that sharks remain clean and crust free, even into old age. For a long time it was thought that sharks move too quickly through the water to give anything any time to settle. Closer inspection of the surface of their skin provided an alternative answer. Sharks are covered in specialised scales called dermal dentacles.

Dentacle means “small tooth”, a name derived the dentine tissue from which they’re made and the same found in your teeth. Dermal dentacles are highly textured, and when meshed together they form an extremely complex surface, full of micro mountains and canyons. This surface appears to be too unstable for any bacteria to settle and establish a community effectively.

Without the base layer of microscopic organisms, the bigger problem of larger, fouler organisms cannot develop, and the shark remains clean and smooth. This evolutionary advantage then helps the seas’ top predators move swiftly through the water in pursuit of their prey.

Shark skin is already well studied, and has inspired a range of products, famously the Olympic grade swimwear that can reduce drag and shave milliseconds of a swimmer’s time. To use it as a surface for hospitals was the idea of Anthony Brennan, founder of the company Sharklet^tm , who have trademarked a textured pattern based on the structure of sharkskin. The company claims that Sharklet^tm surfaces harbour 94% less bacteria than standard worktops and equipment.

Installed in places such as drawer handles and even surgical equipment, Sharklet^tm could be a cost effective way of reducing the spread of bacteria, as well as use of antiseptic and not to mention the time staff spend cleaning surfaces. What has evolved over millions of years could be a solution to a very pressing 21^st century issue.