Chemical Imaging of Cardiac Cell and Tissue by Using Secondary Ion Mass Spectrometry

Abstract

Purpose

Identification and localization of biomolecules in cells and tissue samples are important for understanding of subcellular structures and can be helpful in biomedical and pharmaceutical research.

Procedures

Isolated cardiac cells and tissue of rats are studied by using time-of-flight secondary ion mass spectrometry. This technique provides chemical composition of cardiac cell membrane and tissue surface in native form.

Results

The result is a spatially resolved chemical imaging of cell and tissue surfaces as a lateral distribution of biologically relevant molecules—phospholipids, along with fatty acids, and cholesterol. Phospholipids are represented by phosphatidylcholine and cardiolipin molecules and their fragments. Phosphatidylcholine polar head group at mass of 184.1 u has an origin in the cell membrane, and a two-dimensional distribution of this fragment provides clear chemical contours of the cell. The high-resolution contrast of the cell is observed within its environment represented with Na⁺ ions. Images of PO₄H⁻ fragment and fatty acids with 16 or 18 C atoms are determined in cardiac tissue. Distributions of these 16 and 18 C fatty acids are the same within their groups, and interestingly, these two distribution groups are spatially complementary. Contours of phosphatidylcholine and cardiolipin fragments are also complementary, the distributions of 16 C fatty acids and phosphatidylcholine are identical, and the distributions of 18 C fatty acids and cardiolipin are also the same. This complementarity thus supports the chemical compositions of phosphatidylcholine and cardiolipin based on 16 C and 18 C fatty acids, respectively.

Conclusion

The method provides information not only about cell and tissue morphology, shape, and condition but also about cellular membrane chemical composition and lateral distribution of biologically relevant molecules.