Antibacterial phages combined with
magnetic nanoparticle clusters effectively kill infectious bacteria found in
water treatment systems. A weak magnetic field draws the clusters into biofilms
that protect the bacteria and break them up so the phages can reach them.
The nanoclusters developed through
Rice's Nanotechnology-Enabled Water Treatment (NEWT) Engineering Research Center
carry bacteriophages -- viruses that infect and propagate in bacteria -- and
deliver them to targets that generally resist chemical disinfection. Without
the pull of a magnetic host, these "phages" disperse in solution,
largely fail to penetrate biofilms and allow bacteria to grow in solution and
even corrode metal, a costly problem for water distribution systems.
The Rice lab of environmental engineer
Pedro Alvarez and colleagues in China developed and tested clusters that
immobilize the phages. A weak magnetic field draws them into biofilms to their
targets. Biofilms can be beneficial in some wastewater treatment or industrial
fermentation reactors owing to their enhanced reaction rates and resistance to
exogenous stresses, said Rice graduate student and co-lead author Pingfeng Yu.
"However, biofilms can be very harmful in water distribution and storage
systems since they can shelter pathogenic microorganisms that pose significant
public health concerns and may also contribute to corrosion and associated
economic losses," he said.
The lab used phages that are
polyvalent -- able to attack more than one type of bacteria -- to target
lab-grown films that contained strains of Escherichia coli associated with
infectious diseases and Pseudomonas aeruginosa, which is prone to antibiotic
resistance.
The phages were combined with
nanoclusters of carbon, sulfur and iron oxide that were further modified with
amino groups. The amino coating prompted the phages to bond with the clusters
head-first, which left their infectious tails exposed and able to infect
bacteria.
The researchers used a relatively weak
magnetic field to push the nanoclusters into the film and disrupt it. Images
showed they effectively killed E. coli and P. aeruginosa over around 90 percent
of the film in a test 96-well plate versus less than 40 percent in a plate with
phages alone.
The researchers noted bacteria may
still develop resistance to phages, but the ability to quickly disrupt biofilms
would make that more difficult. Alvarez said the lab is working on phage
"cocktails" that would combine multiple types of phages and/or
antibiotics with the particles to inhibit resistance.
See:
Posted by Dr. Tim Sandle