Think about plasmas and what probably comes to mind is the sort of super-hot fireball found in a nuclear-fusion reactor or the interior of the Sun. Think again, though, because research into the biomedical applications of plasmas has exploded in the last few years.
A case in point is Journal of Physics D: Applied Physics, which has just published a special cluster of papers on the uses of gas plasmas in biology and medicine. Here are some of the highlights:
• Canadian scientists have taken a big step towards developing a plasma-sterilization system capable of killing prions, the agents responsible for BSE (more commonly known as mad cow disease). Prions are notoriously difficult to eliminate, so much so that current sterilization technology requires complete destruction of many contaminated clinical instruments. Now, Caroline Bernard and colleagues of the École Polytechnique de Montréal and Montreal University have come up with a method to detect the effectiveness of prion inactivation. Their approach could one day form the basis of a commercial plasma-sterilization system that destroys prions while leaving clinical instruments intact.
• Biological cells have been successfully transplanted using a miniature plasma torch in pioneering work by scientists at Canada's McGill University. Sara Yonson and colleagues have managed to precisely detach a few cells from their neighbours, pick them up and move them into a different dish without damaging either the cells or the neighbouring tissue. "This is a preliminary step on the road to selected tissue removal [using plasma]," said the team. The work could eventually form the basis of a useful laboratory tool for tissue analysis or even find applications in novel cancer therapies. The plasma torch is also capable of modifying surfaces to promote cell attachment and growth.
• The plasma sterilization of implants and prosthetics needs to be tailored to the specific object, report scientists from Slovenia and Montenegro. Traditional sterilization methods are not suitable for devices that remain inside the body or that are made of polymers. As a result, gentler plasma-sterilization techniques are now widely used in experimental and clinical environments. Little, however, is known about how these plasma methods actually work. Now, though, Uros Cvelbar of the Josef Stefan Institute and colleagues have found that the plasma interacts with the device surface as well as with the bacteria on it - which means that the sterilization process is intrinsically linked to the material type. The researchers suggest that the plasma technique should be modified accordingly to achieve the best results.
• Although argon-plasma coagulation (APC) is a widely used clinical technique, there is still much room for improvement, according to a review by researchers at the German equipment manufacturer ERBE Elektromedizin, Tübingen. APC is a versatile tool used in nearly all areas of surgery to staunch bleeding and shrink tissue. Despite its popularity, though, there is still no clear understanding of the underlying physical processes. What's more, the plasma jets are difficult to control and their effects hard to specify. The authors suggest that improvements in the operating theatre will require closer investigation of the underlying physics.
• Physicists from the University of Iowa have shown how gas flow rate affects the area targeted by a plasma needle. This is a device capable of localized disinfection of an area just a few millimetres across that works quickly and gently. The plasma needle doesn't damage healthy tissue so it has potential applications in many areas of medicine, including cleaning dental cavities and clearing blocked arteries. John Goree and colleagues have succeeded in changing the shape and size of the killing spot it produces by altering the gas flow, and this is a big step towards the eventual clinical deployment of the technology.