On November 20, 2012, a training course on critical point drying (CPD) was held in the Center for Bio-imaging, the CAS Protein Science Core Facility Center at the Institute of Biophysics. The aim of this training was to introduce the principles and applications of CPD, thus developing the skills of users in operating the critical point dryer as well as scanning.

The training was organized by Shufeng Sun, an electron microscopy engineer from the Center for Bio-imaging. Engineer Liang Wang from Ke Yang Co., Ltd. was invited to give a talk. Fifteen users of the scanning electron microscope attended the training.

The training included both lectures and practice exercises. During the lecture session, Shufeng Sun described techniques for preparing biological specimens for scanning electron microscopy. He introduced four different techniques, that is, direct drying, chemical drying, freeze-drying, and critical point drying. He also described the relevant protocols, applications, and advantages and disadvantages of each technique. Liang Wang then presented the history, principles and applications of CPD. He discussed developing trends in Tousimis type critical point dryers. Interaction between the lecturers and trainees on the key points and operational details of CPD was animated. During the practical session, trainees took turns to use the Tousimis Samdri－795 critical point dryer to prepare biological specimens such as fruit flies, ricinus flowers, and cultured cells. The specimens were then scanned by electron microscopy and observed. After carefully analyzing operational procedure and electron microscopy photos, trainees proposed improved protocols based on different specimens.

This one-day training increased trainees’ understanding of CPD and will promote greater use of the critical point dryer at the Center for Bio-imaging. (This training was sponsored by the electron microscopy supplier Zhongjingkeyi Company.)

Fig.3. Drosophilia haltere prepared by CPD and photographed by scanning electron microscopy (Specimens were provided by Jianwen Deng et al.)

Author：Shufeng Sun

Photo provided byJianguo Zhang，Shuoguo Li