Ultrafast microwave energy fixation for electron microscopy.

We demonstrate that microwave (MW) energy can be used in conjunction with chemical cross-linking agents to fix tissue blocks rapidly for electron microscopy in as brief a time as 26 msec. The optimal ultrafast MW fixation methodology involved immersing tissue blocks up to 2 mm3 in dilute aldehyde fixative and immediately irradiating the specimens in a 7.3 kW MW oven for 26-90 msec, reaching a fixation temperature range of 32-42 degrees C. Ultrastructural preservation of samples irradiated by MW energy was comparable to that of the control samples immersed in aldehyde fixative for 2 hr at 25 degrees C. Potential applications for this new fixation technology include investigation of rapid intracellular processes (e.g., vesicular transport) and preservation of proteins that are difficult to demonstrate with routine fixation methods (e.g., antigens and enzymes).