Applying secondary ion mass spectrometry to the analysis of elements in goblet cells of conjunctiva.

Abstract

We investigated the location of elements in the goblet cells of rat conjunctiva by analyzing ion images produced by secondary ion mass spectrometry (SIMS) and comparing them with those produced by energy dispersive X-ray analyser (EDX). Conjunctivas of normal Spraque-Dawley rats were quenched in propane prechilled liquid nitrogen. Semi-thin sections were made with a cryo-ultramicrotome, freeze-dried, carbon-coated and observed under a light microscope, SIMS and scanning electron microscope (SEM). In the element analysis by SIMS, images of positive ions were examined with an O2+ primary ion source and images of negative ions with a Ga+ ion source. The same sections were observed and analysed with SEM-EDX. Morphological features and images of elements with SIMS and EDX were compared. Na, Mg, K, and Ca were detected as positive ions and OH, CN, P, S, and Cl as negative ions with SIMS, but C, N, O, Na, Mg, P, S, Cl, K, and Ca were detected with EDX. The spatial resolution of SIMS in element location was higher than that of EDX. Many elements were clearly located in the goblet cells on ion images by SIMS. Element ion images were demonstrated more densely in goblet cells than in other parts within conjunctiva and by SIMS compared to EDX. SIMS is a useful method for the detection of elements and their locations in ocular tissues and cells.