Graphene-wrapped particles kill drug-resistant bacteria in wastewater
Antibiotic-resistant bacteria are emerging as a serious public health threat, and part of the reason is that the bugs can pass resistance genes to each other. Now, researchers at Rice University have developed a system using nanoparticles wrapped in graphene oxide to kill both the superbugs and their free-floating resistance genes in wastewater.
Bacteria are community-minded organisms, so when some of them figure out how to resist antibiotics, they’re quick to spread that ability to others to help them survive. These antibiotic-resistance genes (ARGs) can persist in environments like wastewater plants and escape into natural waterways, supercharging bugs that haven’t directly encountered drugs themselves.
That means it’s often not enough to just kill the bacteria themselves – those loose genes will just spawn more superbugs. So scientists are investigating ways to prevent bacteria from spreading those genes, as well as how to clean up both bacteria and ARGs at the same time.
The new study sits in the latter category, describing a new disinfecting system for use in wastewater treatment plants. The core of the new technology are photocatalysts in the form of “nano-spheres” made of bismuth, oxygen and carbon. When stimulated by light, these produce molecules called reactive oxygen species (ROS), which are deadly against bacteria and ARGs alike.
In tests against multi-drug-resistant E. coli, the team found that these nano-spheres performed better if wrapped in a protective shell made of graphene oxide. This layer reduced the number of ROS that were destroyed by scavengers in the environment, letting them produce three times more ROS than the uncovered spheres.
As an added improvement, doping these graphene oxide shells in nitrogen helped the spheres capture more bacteria, giving them more time to kill the bugs and the ARGs they may drop after they die.
“Wrapping improved bacterial affinity for the microspheres through enhanced hydrophobic interaction between the bacterial surface and the shell,” says Pingfeng Yu, co-lead author of the study. “This mitigated ROS dilution and scavenging by background constituents and facilitated immediate capture and degradation of the released ARGs.”
The researchers also say that the spheres are large enough to be filtered out of the water and reused several times. In tests, the team showed that even after being reused 10 times, the spheres retained the vast majority of their photocatalytic activity.
The research was published in the journal Water Research.
Source: Rice University