Sharp marketing

Sharp Corporation seems to have pulled off a marketing coup with the announcement that its Plamacluster Ions (TM) device is effective against airborne influenza H5N1 and many other pathogens. We have examined the technical basis for the claims to understand them better.

"Plasmacluster Ion technology" is a tradename for a device that produces hydroxyl radicals, a well known method for disinfection and purification. What Sharp seems to have done is to work with non-company researchers to test a household sized unit against a fairly wide variety of organisms to show its effectiveness in killing or inactivating them under laboratory conditions. Sharp describes this as a “collaborative research approach to product marketing.” The demonstration some years ago that the mechanism of deactivation of bacteria and fungi by such devices was through damage of cell membrane and surface proteins suggested it might also be effective against viruses whose surface proteins are important for their life cycle. Influenza viruses, which have hemagglutinin (H) and neuraminidase (N) proteins protruding from their viral coats are examples. Influenza A virus must first dock with a host cell before infecting it. The hemagglutinin protein is central to finding the docking site on the host cell's surface. A reasonable speculation is that alteration of the H-protein on the viral surface makes this docking impossible, although the exact mechanism was not stated on the Sharp website and it is likely it is not known.

Plasmas are sometimes called the "fourth state of matter" (after gases, liquids and solids) and consist of a gaseous mixture of positively and negatively charged ionized atoms and molecules. Plasmas sound exotic (and are not that common in terrestrial environments), but it has been estimated that they constitute more than 99% of the matter in the universe, filling interstellar space. They are behind such visible phenomena as the Northern Lights, fluorescent and neon bulbs and lightning. Generating a plasma takes energy and there are various ways to do this. The Sharp device appears to work by using a high electric potential to strip electrons off water molecules (H-O-H) to form H+ and O₂- ions. These ions are surrounded by other water molecules in the air forming "cluster ions" of H+ or O₂- ions (water on the outside, ions inside). Hence "plasmacluster" technology. The ion clusters are attracted to airborne particles on whose surface they react with each other to form hydroxyl radicals, highly reactive chemical species that readily combine with hydrogen atoms on other compounds, including proteins. At least that is how I reconstruct the Sharp explanation, which is more than a little vague. Unlike negative ion generators, little ozone is produced.

Here is Sharp's description of its testing procedure:

A Plasmacluster Ion Generator was placed in a box with a volume of one (1) m3, and Plasmacluster Ions were generated (concentration: 7000 ions/cm3). Then, aerosolized highly pathogenic avian influenza virus was sprayed into the box. Five minutes after the spraying was complete, the air in the box containing the airborne virus was sampled at 10-minute intervals. The virus was then extracted and injected into cell cultures. Changes in the cells were then observed over a four-day period.

Four days after injection, the cells injected with the virus that had not been exposed to Plasmacluster Ions were deformed and damaged. In contrast, cells injected with the virus that had been exposed to Plasmacluster Ions retained their normal condition with almost no change in evidence.

From this, it was confirmed that Plasmacluster Ions can reduce the activity of the virus by 99%. (The TCID50 [Tissue Culture Infectious Dose 50%] assay, which is widely used in the field of virology, was used to evaluate the test results.)

What we learn from this (assuming the accuracy of the description) is that under the conditions of the test, the Sharp device was capable of inactivating H5N1 virus, as measured by its ability to infect MDCK cells (cells derived from dog kidneys) in tissue culture. It is not unreasonable to suppose this has some bearing on the ability of the device to protect people against airborne virus as well, although much needs to be specified further, such as whether under usual environmental conditions the same results apply (e.g., there is not a "natural demand" from interfering microparticles prevent it from taking care of the virus and that the amount of inactivation is sufficient to reduce risk). More importantly, the relative contribution of suspended airborne microparticles in influenza transmission compared to contact with contaminated surfaces, hands or large droplets (as from a cough or sneeze) that will have insufficient contact time and too small a surface area to volume ratio to make the device work is unknown, so the ability of devices like this to interrupt epidemic transmission is unclear. It may find use in certain specialized environments.

One thing seems clear. At roughly $800/unit to take care of a typical 300 square foot room, increased public concern over an avian influenza threat will be very effective in increasing the revenues of Sharp Electronics.