Bacteriophage-nanocomposites: An easy and reproducible method for the construction, handling, storage and transport of conjugates for deployment of bacteriophages active against Pseudomonas aeruginosa

• This paper details development of a novel, cost effective protocol for the binding of bacteriophages without loss of function.
• Bacteriophage-nanotube conjugates were efficacious after storage at 20 °C for six weeks.
• Retention of viral infective potential was demonstrated by subsequent spread plating on to lawns of susceptible P. aeruginosa.
• Bacteriophage-nanotube conjugates were added to human cell culture in vitro for 9 days without causing necrosis and apoptosis.
• Analysis of the human cell culture medium revealed an initial but not long lasting interleukin response.

The purpose of this work was proof of concept to develop a novel, cost effective protocol for the binding of bacteriophages to a surface without loss of function, after storage in various media. The technology platform involved covalently bonding bacteriophage 13 (a Pseudomonas aeruginosa bacteriophage) to two magnetised multiwalled carbon nanotube scaffolds using a series of buffers; bacteriophage–nanotube (B–N) conjugates were efficacious after storage at 20 °C for six weeks. B–N conjugates were added to human cell culture in vitro for 9 days without causing necrosis and apoptosis. B–N conjugates were frozen (− 20 °C) in cell culture media for several weeks, after which recovery from the human cell culture medium was possible using a simple magnetic separation technique. The retention of viral infective potential was demonstrated by subsequent spread plating onto lawns of susceptible P. aeruginosa. Analysis of the human cell culture medium revealed the production of interleukins by the human fibroblasts upon exposure to the bacteriophage. One day after exposure, IL-8 levels transitorily increased between 60 and 100 pg/mL, but this level was not found on any subsequent days, suggesting an initial but not long lasting response. This paper outlines the development of a method to deliver antimicrobial activity to a surface that is small enough to be combined with other materials. To our knowledge at time of publication, this is the first report of magnetically coupled bacteriophages specific to human pathogens which can be recovered from test systems, and could represent a novel means to conditionally deploy antibacterial agents into living eukaryotic systems without the risks of some antibiotic therapies.