An Athlone-based researcher is studying a new device that sterilises surgical instruments with a zap of electricity rather than with chemicals or antibiotics, writes Dick Ahlstrom.
The hospital superbug can survive cleaning agents and antibiotics, but it has no chance against a short pulse of electricity. A novel technique involving high-voltage pulses lasting as little as a millionth of a second may become the best way yet to kill off microorganisms.
The approach does not involve chemicals or drugs that can lead to antimicrobial resistance. It also has a very green side given its low power demand, explains Dr Neil Rowan of the department of nursing and health science at Athlone Institute of Technology (IT).
Dr Rowan, who heads Athlone's Biomedical and Health Science Research Group, received funding worth €160,000 from Science Foundation Ireland to study how the technology might be used to kill off the superbug MRSA and also the agent that causes variant Creutzfeldt Jakob Disease (vCJD).
Dr Rowan's centre has already received €1.4 million to support collaborations with groups in University College Dublin, NUI Galway and Strathclyde University. This helps to fund seven postgraduate students attached to the group, says Dr Rowan.
He is a trained microbiologist but has also studied pulsed electric fields. These subjects merge in his current work at Athlone IT, which builds on studies of pulsed power technology conducted while he was based at Strathclyde.
Most organisms, notably MRSA, develop resistance to bactericides and antibiotics over time. "Microorganisms have an adaptive ability that makes them become resistant, but they have no prior exposure to electrical fields," says Dr Rowan.
The new funding will be used to study the sterilisation of medical devices and surgical instruments without chemical biocides. Instead a powerful 40,000-volt electrical field is used to produce a "cold plasma", Dr Rowan explains.
Importantly, the field is pulsed, with pulses lasting anything from one second down to less than a microsecond. In this way a "huge energy is delivered very quickly" over a relatively small space, he says.
In practice, such a device for cleaning and sterilising would require a watertight chamber big enough to hold surgical tools. The chamber is filled with water and then oxygen is bubbled through as the pulsed 40,000-volt potential is applied across two electrodes in the chamber, explains Rowan.
The energy disassociates the oxygen to form a "cold plasma". In use, prototype devices do not raise the water temperature by more than a degree or two, and there is very little arcing to metal instruments given the water bath, Rowan says. Other physical effects take place however, all of which contribute to the system's ability to kill off even the toughest microorganisms.
Excited atoms and molecules emit light at ultraviolet wavelengths which are lethal to bacteria by penetrating to the cell nucleus and disrupting DNA. It produces acoustic shock waves within the fluid, and the field also creates free oxygen radicals and ozone, which break down the bacterial protein coat, Dr Rowan explains. Ozone levels of up to 5,400 parts per million have been achieved, he says.
The plasma alone is enough to clean and sterilise, he says. "If you form a plasma on a surface it removes proteinacious material and other organisms."
Yet the technique also delivers the other sterilising effects including reactive oxygen and UV. "Collectively it is quite good for knocking out organisms."
Preliminary tests show it is highly effective against bacteria of all sorts but also organisms such as Cryptosporidium and fungal spores, Dr Rowan says.
Athlone has embarked on a number of collaborations to assess the microbial effectiveness of the system. It will also gauge the technique's ability to denature prions, the protein agents that cause vCJD.
Such a device could be used in many other ways, Dr Rowan adds. For example, it could be used to kill off E coli and salmonella in waste water from poultry processing plants and to sterilise other effluent outflows.
Its low power demand also makes it green, he believes. Only short exposure periods are sufficient to kill off bacteria, even with as few as 50 pulses. "It's a really clever way of energy delivery," Dr Rowan adds.