LOW VACUUM SCANNING ELECTRON MICROSCOPY (LVSEM) FOR INTEGRATED MICROSCOPIC EVALUATION OF IMPLANTABLE DEVICES

Abstract

Scanning electron microscopy (SEM) can be used to evaluate tissue/ implantable device interfaces at high magnification. However, specimens prepared for SEM often cannot be used for subsequent light microscopy (LM) or transmission EM, thus ruling out direct correlation of SEM, LM, and TEM findings for one specimen. LVSEM may circumvent this problem. The techniques used to prepare specimens for LVSEM are similar to those for LM and TEM. First, the specimen is fixed, then dehydrated with graded ethyl alcohol to absolute alcohol. Then, the specimen is dried; mounted and secured on an alL/minum stub; and examined in a microscope equipped for LVSEM USM-5900LV) under low vacuum. For evaluating biologic specimens from stents or catheters, optimal settings are 10 kV, Spot 40, and 18–40 Pa. The principal advantage of LVSEM over traditional SEM is that the specimen evaluated can still be subjected to LM and TEM. As we have found, this can reduce costs and minimize the number of animals needed. Moreover, by using the Exakt™ plastic embedding and microgrinding system, LM findings can be directly correlated with TEM findings. LVSEM provides an excellent tool for locating and identifying the types of tissue that may be adhering to a device. In such cases, the adherent tissue can be removed and then evaluated by LM and/or TEM. In conclusion, LVSEM is a potentially powerful new technique that allows for more precise qualitative and quantitative evaluation of interfaces between tissue and implantable devices.