Chemical imaging of cardiac cell and tissue by using secondary ion mass spectrometry.

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 PO(4)H(-) 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.