Blasting Biofilms with Plasma Torches

Killing a fungus doesn't mean you are free from its infectious grasp. You see many pathogenic fungi (and bacteria) grow in what is referred to as a biofilm, and killing the fungus doesn't make the biofilm magically disappear. If you think for a second that is obvious; killing a person wouldn't make the body go away, if it did the boys from Pulp Fiction would never have called in The Wolf.

Anyway, the biofilm is the complex of organisms living together in a self created extracellular matrix. That matrix does a number of things; it supplies a structure for the colony, holds some of the nutrients from the surrounding environment, and it offers protection from things like host responses and microbial forces.

Obviously killing the pathogen itself is the number one goal, but without actual removal of the infector, the host is still open to inflammation and secondary infection. Biofilms of pathogens are involved in well over half of infections contracted by once in a hospital. The problem is that conventional cleaning and disinfecting procedures biofilms often remain. It is for this reason that a new study has attempted to see the potential effectiveness of Plasma Torches on biofilms... Ok, technically Low-Temperature Atmospheric Pressure Plasma, but come on this is a torch:

Biofilm blasting Plasma Torch, driven with 5 slm Ar and
0.05 slm O₂, impinging a polymer surface.

Plasma treatment has been shown to be effective in killing pathogens and has been extensively studied in sterilizing and cleaning biomedical materials. But what about its potential for combining these aspects into killing and removal of biofilms in one awesomely torch-tastic moment?

A new study by researchers out of Germany seeks to answer this question. The team basically grew Candida albicans biofilms on a flat surface and blasted the hell out of it with an Argon plasma jet, and then also with a combination jet of Argon and Oxygen. They then used microscopic imaging to detect whether or not there was any biofilm remaining.

Atmospheric Pressure Plasma: A High-Performance Tool for the Efficient Removal of Biofilms

C. albicans is a good model for this study because it is one of the most prevalent biofilm creating pathogens. It is known to colonize pretty much everything from dental materials to prostheses and is responsible for some majorly life threatening infections.  And it is also a fungus, so I get to talk about this study.

The team grew C. albicans on a Polystyrene wafer that was pre-treated to enable a uniform colony growth on its surface. They did this by growing the fungus in a broth and then transferring a sample onto the wafer. The samples were incubated for 7 days, with a medium change every twenty-four hours, and then wafers were washed with a saline solution to remove any left overs.

And now for the plasma treatment.  Since previous studies suggested that a small distance allowed for the greatest plasma etching, the scientists held a constant distance of 7mm between the nozzle and sample. They then proceeded to subject the C. albicans, along with its biofilm matrix, to 60, 120, 180 and 300s of Argon plasma jet. They used a control that was exposed to the gas without full on plasma ignition. They repeated this with the aforementioned mix of Argon with a hint of Oxygen.

At 300s the Argon plasma did its initial job, killing C. albicans, but it didn't quite have the up-and-at-em to completely remove the biofilm entirely. However, as you can see in the below picture, adding some good 'ol Oxygen to the Plasma made for a clean wafer. The major caveat is that a plasma jet treatment is localized; I mean it can only hit the pathogen directly in front of it.

So, while more testing is always a good thing, this study demonstrates the potential use of Non-thermal plasma in efficiently removing C. albicans biofilms from surfaces. This could open up new possible sterilization and bio-decontamination techniques. Plus maybe it is the first step down the road to get a Plasma globe into every laboratory like on old sci-fi shows.

Awesome Researchers:
Katja Fricke, Ina Koban, Helena Tresp, Lukasz Jablonowski, Karston Schroder, Axel Kramer, Klaus-Dieter Weltman, Thomas von Woedtke, & Thomas Kocher (2012). Atmospheric Pressure Plasma: A High-Performance Tool for the Efficient Removal of Biofilms PLoS One DOI: 10.1371/journal.pone.0042539

Additional Photo Cred(Plasma ball):
Blaise Frazier aka PiccoloNamek via WikiCommons