Carbon steel is relatively hard compared to stainless steel and a carbon steel blade will keep its cutting edge longer when used in a clean and dry application; however, it has the inherent disadvantage that it will rust quickly when exposed to moisture. Hence to prevent rusting in storage, carbon steel blades have a film of oil that must be removed before the blade can be used. The corrosion process is, of course, accelerated significantly in saline such as artificial cerebral spinal fluid (aCSF).
For these reasons, normal razor blades and carbon steel blades are not recommended for precision tissue sectioning. Campden Instruments supply two types of blades for the 9000SMZ vibrating microtome:
CI.7550-1-SS/50 Stainless-Steel Blades
Made from surgical quality stainless steel, these blades are double bevelled on both faces and are honed to an acute cutting edge. Because of the relative softness of stainless steel, for optimum performance it is recommended that stainless steel blades should only be used once per tissue sample undergoing slicing or changed at the beginning of each day. Notes on best practice may be found on the 9000SMZ Support Hub webpage.
CI.7550-1-C Ceramic Blades
Made from ultra-hard zirconium, this is a material that can be lapped to the finest of edges. The body of the blade is very rigid which maintains a straight cutting edge. The result is that slice quality is substantially improved with prolonged slice life, especially in the most difficult tissues. Additionally, the blade has a much longer life due to the ultra-hard cutting edge not losing its sharpness and being impervious to corrosion.
For studies where the deposition of metal into the slice would have undesirable effects, the benefit of ceramic blades is clear. The initial higher cost of the ceramic blade is more than offset by its longevity.
To facilitate the fitting of the narrow blades a special blade holder tool is provided. This helps ensure correct blade alignment and reduces the risk of personal injury when fitting the blade. Further details are shown in Section 8.
The 9000SMZ instrument is supplied with a fixed angle titanium blade holder suitable for the CI.7550-1-SS/50 stainless steel and CI.7550-1-C ceramic blades. Sample blades are included with each instrument.