Bacteria-killing spikes for food production surfaces

An RMIT University study has suggested that rough surfaces inspired by bacteria-killing spikes on insect wings may be more effective at combatting drug-resistant superbugs, including fungus, than previously understood.

RMIT scientists have designed a pattern of microscales spikes that can be etched onto titanium implants or other surfaces to provide drug-free protection from bacteria and fungus. It could also have applications for stainless steel benches used in food production and agriculture.

The study, published in Advanced Materials Interfaces, tested the effectiveness of the altered titanium surface in killing multidrug-resistant Candida – a potentially deadly fungus responsible for one in 10 hospital-acquired medical device infections.

The specially designed spikes, each of a similar height to a bacteria cell, destroyed about half the cells soon after contact. Significantly, the other half not immediately destroyed were rendered unviable from the injuries sustained, unable to reproduce or cause infection.

The surface’s effectiveness against common pathogenic bacteria including golden staph was demonstrated in an earlier study published in Materialia.

Candida destroyed on microspikes tilted view.

Group leader Distinguished Professor Elena Ivanova said the latest findings shed light on the design of antifungal surfaces to prevent biofilm formation by dangerous, multidrug-resistant yeasts.

“The fact that cells died after initial contact with the surface — some by being ruptured and others by programmed cell death soon after — suggests that resistance to these surfaces will not be developed,” she said.

“This is a significant finding and also suggests that the way we measure the effectiveness of antimicrobial surfaces may need to be rethought.”

Advances have been made over the past decade in designing surfaces that kill superbugs on contact. However, finding the right types of surface patterns to eliminate 100% of microbes so some don’t survive to become resistant is an ongoing challenge.

“This latest study suggests that it may not be entirely necessary for all surfaces to eliminate all pathogens immediately upon contact if we can show that the surfaces are causing programmed cell death in the surviving cells, meaning they die regardless,” she said.

RMIT’s Multifunctonal Mechano-biocidal Materials Research Group has been developing antimicrobial surfaces inspired by the nanopillars covering dragonfly and cicada wings for over a decade.

Ivanova’s team has spent the past decade replicating these nanopillars, with this latest advance achieved using a technique called plasma etching to create the antibacterial and antifungal pattern in titanium.

The technique could also be optimised and applied to a range of materials and applications, such as the stainless steel benches used in food production and agriculture.

Top image caption: Group leader Distinguished Professor Elena Ivanova with her team.