Scientists in the US have invented a new material that makes urinary catheters, intravenous catheters, and implants so slippery, life-threatening colonies of E. coli and Staph bacteria struggle to accumulate on them.
It’s estimated that biofilms - adhesive colonies of harmful bacteria that form on medical equipment - are responsible for more than 80 percent of all microbial infections in the body, and there are a select few species of bacteria that are becoming increasingly difficult to deal with in hospitals, even with copious amounts of antibiotics on hand.
For example, urinary tract infections (UTIs) represent 40 percent of all hospital-acquired infections, and 11 percent of those are caused by the bacterium Pseudomonas aeruginosa. In fact, P. aeruginosa currently accounts for up to 15 percent of all hospital-acquired infections in the US, and it’s notoriously resistant to the drugs we try to combat it with. Two of the most significant human pathogens, E. coli and Staphylococcus epidermidis, are similarly troublesome, causing all kinds of tissue and blood infections thanks to their continued and widespread existence in even the world’s cleanest and best-staffed hospital environments. If you're really unlucky, you could go in for a routine surgical procedure, and die from a severe bacterial infection.
Long story short, we need better ways of keeping our medical equipment free from bacteria, and antibiotic treatments are becoming less and less of an option.
So a team led by chemist Joanna Aizenberg from the Kavli Institute for Bionano Science and Technology at Harvard University has come up with a solution: commercially available silicone tubing - the same kind that’s already being used in today’s medical tubing - infused with high-purity silicone oil. This silicone mixture releases a self-lubricating, slippery coating that’s super-repellent, long-lasting, non-toxic, and cheap to produce.
Suitable for all kinds of medical surfaces, including those of mechanical heart valves, urinary catheters, intravenous catheters, and implants, this silicone material has been engineered to take up and store large amounts of lubricating silicone oil in its molecule structure, just like a sponge. This means where ever it’s used, the substance will form a smooth lubricant layer over the surface, making it a whole lot more difficult for bacteria to hold on to and colonise the area.
“The solid silicone tubing is saturated with silicone oil, soaking it up into all of the tiny spaces in its molecular structure so that the two materials really become completely integrated into one,” one of the team, Caitlin Howell, said in a press release.
And the best part is it doesn’t lose its slipperiness over time, because the silicone oil is only released onto the surface of the silicone when needed, so to replace any oil that’s been wiped away by other liquids such as urine, blood, or gastro-intestinal fluids.
To test their new coating, the team exposed treated and untreated medical tubing to P. aeruginosa, E.coli, and Staphylococcus epidermidis. They found that the silicone oil-infused tubing greatly reduced bacterial adhesion and largely eliminated biofilm formation.
The researchers discuss their results in the journal ACS Biomaterials Science & Engineering:
"We have demonstrated that P. aeruginosa biofilm formation can be reduced in various shear conditions, including those representative of indwelling catheters, by at least 10-fold. After a five-second wash with water, the biofilm volume can be almost completely removed, while a robust biofilm remained on the untreated control silicone surfaces. Further, the materials passively resist bacterial accumulation without the use of bactericidal agents, and could thus be developed as an important component in reducing excessive antibiotic usage."
“With widespread antibiotic resistance cropping up in many strains of infection-causing bacteria, developing out-of-the-box strategies to protect patients from bacterial biofilms has become a critical focus area for clinical researchers,” added one of the team, bioengineer Donald Ingber, in the press release. “Liquid-infused polymers could be used to prevent biofilms from ever taking hold, potentially reducing rates of infection and therefore reducing dependence on antibiotic use.”
The next step is to get FDA approval so the new material can be used in hospitals. As the silicone parts have already been approved, this will hopefully only take a couple of years. The team is also now working on expanding the technology to other applications, such as keeping the surfaces of waste-water management systems, maritime vessels, and oil pipes clean.
“Each technology in our portfolio has different properties and potential uses, but collectively this range of approaches to surface coatings can prevent a broad range of life-threatening problems,” says Aizenberg, "from ice accumulation on airplane wings to bacterial infections in the human body.”
Game on, bacteria.