Bio-imaging and serum analysis of zinc and other trace elements in a study of age-related diseases using inductively-coupled plasma mass spectrometry

Trace elements participate in numerous biological processes and understanding their activity is essential in monitoring various diseases. Zinc has long been recognized as a fundamental component of various tissues, being highly concentrated in the retina and an essential structural component of many proteins. It plays a crucial role in many biological activities including homeostasis, immune function, oxidative stress, and aging disorders. During aging, the systemic metabolism of iron, zinc and copper changes, and this disruption in metal homeostasis appears to be associated with age-related disorders such as Alzheimer s disease (AD) and Age related macular degeneration (AMD). As understanding the role of these metals is critical in finding the underlying causes for such diseases, and providing proper diagnosis and treatments, the distribution of these crucial elements in AD and AMD has been investigated. A rapid, accurate technique using sector field inductively coupled plasma mass spectrometry (SF-ICP-MS) was developed for the preparation and analysis of small volume (30 µl) biological samples. Analytical performance was evaluated using Serum UTAK certified reference material and the method was applied to Zn, Cu and Fe determination in 81 human serum samples from AD and AMD patients. No significant difference was found in Zn and Cu levels between AD and AMD patients, whereas Fe in AMD patients was slightly higher than AD patients. The results showed a decrease in serum Zn and Fe, and a notable increase in serum Cu in both AD and AMD patients compared to healthy controls. Elemental bio-imaging using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was successfully employed for Zn imaging in 12 rat retina sections given either a conventional or a Zn-containing diet. A new data processing method, involving fitting Gaussian peaks to individual LA-ICP-MS line scans, was established. The RPE/retina peak area ratio was used to evaluate the differences in Zn content between supplemented and non-supplemented rats. In general, the difference between the three differentially fed rat groups was not statistically significant for the relatively small group of twelve rats investigated here. Thickness of Zn bands was also found to vary between controls and supplemented rats. This technique has the potential to support biologists in recognising possible new biomarkers for disease, related to specific trace elements.