Cold plasma, a hot ticket for hospital hygiene
Researchers working on BIODECON, an EU funded project, are developing a novel method involving cold plasma discharges to sterilise medical instruments. Unlike existing technologies, they say that the plasma discharge could destroy bacteria, viruses, and prions without damaging the instruments themselves. The project is funded under the 'New and emerging technologies' (NEST) section of the Sixth Framework Programme (FP6). Hospital surgical procedures must be conducted using sterile instruments and supplies. While supplies such as gloves, surgical blades, and suture materials are commercially available in sterile packs, many surgical instruments have to be sterilised in-house. To date, methods involving highly toxic chemicals and high temperatures have been used to decontaminate the surfaces of medical paraphernalia. However, these methods have severe drawbacks, according to Professor Achim von Keudell, BIODECON's project coordinator, To get rid of a pathogen using highly toxic chemicals, instruments are washed in the chemical mixture for about one minute. Instruments are then rinsed in distilled water for about an hour to remove the traces of the toxic chemicals. 'This is a very long treatment time which not only uses a lot of energy but also produces a large amount of waste, since the toxic chemicals have to be disposed of afterwards,' Professor von Keudell told CORDIS News. In procedures where high temperatures are needed, it can happen that the instruments or medical equipment are damaged. 'Polymers like those found in implants cannot be exposed to high heat or aggressive toxic chemicals since the plastic would dissolve,' explained Professor von Keudell. Because some devices cannot withstand these sterilisation procedures, they can only be used once. So expensive instruments like the catheter, a polymer tube that can be inserted into a body cavity duct or vessel, are thrown away after one use. Another problem is how sterilisation methods are validated. To date, methods only have to prove that they can kill off endospores or bacteria. But medical equipment can also hold traces of viruses and biomolecules like the 'prion' proteins that cause Creutzfeldt-Jakob. These can be fatal for patients. 'The standard argument has been that if a sterilisation method can inactivate bacteria, it will be able to inactivate prions or viruses,' explained Professor von Keudell. 'But we know that this is not true. If you sterilise a scalpel with traces of prions, you will see afterwards that it is still infected.' The cold plasma discharge methods currently under development by the BIODECON project consortium target all three types of contaminants. A plasma discharge is a gas containing energetically excited and ionised particles, which is created when electricity ignites the gas. The excited particles in the plasma react with and destroy the bio molecules, rendering toxins and pathogenic micro-organisms harmless. The researchers are exploring the potential of plasma at a range of low and high pressures, using a variety of source gases including oxygen fluorine hydrogen, nitrogen and argon. According to Professor von Keudell the plasma procedures can inactivate bacteria and biomolecules much more quickly than traditional methods. 'The typical plasma sterilisation process has two time constants. In a matter of seconds the topmost lying bacteria are killed by the intense UV light. You then need a couple of minutes for the plasma to reach also lower lying layers of bacteria on the sample,' he explained. Also unique to this novel method is the fact that the surface of an instrument does not have to be heated for the plasma to take effect. This means that medical equipment can be decontaminated without being damaged. However, there are some obstacles to overcome before the plasma procedures are ready to be used, says Professor von Keudell. 'If you have to remove a lot bacteria, say in a thick layer, then the plasma process will take much longer and use up more energy and chemicals, and will therefore be more expensive,' he explained. 'You might then have to think of a two-step process combining a traditional sterilisation method with a plasma one.' Procedures would also have to be adapted to tackle bacteria and biomolecules when enveloped in a matrix like blood, fat or living tissues. Finally, plasma technologies would also have to be adapted to deal with medical equipment like tubing. 'It would be easy to use plasma to sterilise something in a narrow volume like a tube from the outside, but not so easy to get to the inside. Methods using chemicals are still the preferred choice since it is not hard to guide a liquid through a tube,' says Professor von Keudell. Despite these obstacles, the professor believes that there is a 'fair chance' that the plasma methods under development will be validated. As for bringing a plasma sterilisation device to the market, Professor von Keudell explained that the consortium would first need to find industrial partners willing to invest in developing a prototype. At its mid-term meeting in June, the project consortium will meet with industrial advisors, who will give their thoughts on the market potential of the research.
Countries
Germany, France