Investigation of Heavy Metals in Zebrafish Tissue by Total Reflection X-ray Fluorescence

Heavy metals are present in the environment, in many consumer products and can be found in food. Some heavy metals like zinc and copper are essential for enzymatic and metabolic function while others like lead and mercury are toxic and interfere with biological pathways. Zebrafish are a very popular model organism for monitoring toxicity of heavy metals and investigating vertebrate development. In this study we explore the possibility of using total reflection X-ray fluorescence spectrometry to analyze histological sections of zebrafish embryos after exposure to nickel and lead. A methacrylate resin embedding protocol and a paraffin embedding protocol were evaluated as possible options for sample preparation for TXRF analysis of zebrafish embryos. It was found that paraffin is the superior material after an alkaline phosphatase stain was introduced. The stain made the normally transparent fish embryo embedded in paraffin clearly visible on the sample reflector material thus allowing for easy positioning and identification of the area of interest.