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Electro-elution - Development of a method to remove infectivity from surgical instruments -Trust Sterile Services, Bellshill, Scotland.


 The Transmissable Spongieform Encephalopathies (TSE's) are a group of infections including scrapie (in animals) and mad cow disease and CJD in humans. They are believed to be caused by proteins known as prions. Prions are unusual in having two three dimensional shapes in which they are stable. In their normal coiled form, prions are a normal part of the cell markers that signal the immune system to report that all is well.  However, if these proteins flip form a coiled (PRPc) (spiral) form to a folded (PRPsc) (beta pleated sheet) configuration (like folded rolls of computer paper) they are believed to be the causative agent of the TSE degenerative brain diseases.

CJD infectivity is believed to have been removed from the British food chain (Note CJD has now been identified in wild game in the US which has caused the death of a number of hunters who have eaten them). However, recently it has been demonstrated that CJD can be transmitted from infected to non infected patients through neurosurgical instruments. Prion protein binds firmly to steel and is not removed by normal cleaning methods or destroyed by autoclaving or soaking in disinfectants.

The Osmosis Unit was invited to  investigate this problem and determine a method of removing TSE infectivity from surgical instruments that could be used as a normal part of normal reprocessing of surgical instruments.

Brain is a very sticky material which binds firmly onto stainless steel. Our research demonstrated that the binding was made worse if alcohol (a material used liberally in operating theatres) also comes in contact with the infected instrument. We published our findings in the Journal of Hospital Infection ( Prior FGR, Fernie K, Renfrew A, Heneaghan G. Alcoholic fixation of blood to surgical instruments - a possible factor in the surgical transmission of CJD. J Hosp Infection,  2004; 58: 78-80). 

Consideration of the chemistry of the process led to the suggestion that large proteins may be able to cold electroplate onto steel. In this case, removal of prion should be possible by reversing this electroplating process. We constructed a electro-elution prototype in which the protein contaminated instrument is held as the cathode of an electrolytic circuit. Tests showed that blood, alcohol fixed blood and homogenised brain were removed from steel surfaces in about 3-4 minutes. Testing the process more thoroughly by using a Cleaning test disk demonstrated that the difficult to clean parts such as the box joint and the inside of catheter lumen were cleaned in less than 20 minutes. A patent for the process has been filed. Initial tests suggest that not only is PRPsc removed but is denatured in the electrolyte. A partner is now being sought to convert the prototype into a full scale instrument cleaning device.

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Last modified: 07/05/06