Chemical fixation creates nanoscale clusters on the cell surface by aggregating membrane proteins

Chemical fixations have been thought to preserve the structures of the cells or tissues. However, given that the fixatives create crosslinks or aggregate proteins, there is a possibility that these fixatives create nanoscale artefacts by aggregation of membrane proteins which move around freely to some extent on the cell surface. Despite this, little research has been conducted about this problem, probably because there has been no method for observing cell surface structures at the nanoscale. In this study, we have developed a method to observe cell surfaces stably and with high resolution using atomic force microscopy and a microporous silicon nitride membrane. We demonstrate that the size of the protrusions on the cell surface is increased after treatment with three commonly used fixatives and show that these protrusions were created by the aggregation of membrane proteins by fixatives. These results call attention when observing fixed cell surfaces at the nanoscale. Atomic force microscopy imaging shows that cell fixation can lead to unwanted aggregation of membrane proteins.

Automated summary

Chemical fixatives have been found to potentially affect the nanoscale structures of cell surfaces by inducing aggregation of membrane proteins. However, research in this area has been limited due to the lack of methods for observing cell surface structures at the nanoscale. In this study, a method using atomic force microscopy and a microporous silicon nitride membrane was developed to observe cell surfaces with high resolution. The results showed that commonly used fixatives increased the size of protrusions on the cell surface, indicating the aggregation of membrane proteins caused by the fixatives.