The Analytical BrainMet (Bioimaging of Metals in Brain and Metallomics) Centre at the Forschungszentrum Jülich, Germany, has developed novel mass spectrometry imaging (MSI) techniques using laser ablation-inductively coupled plasma-mass spectroscopy (LA-ICP-MS) to advance dementia research by studying the effects of metals and metalloproteins in thin cryosections of brain tissue in respect to the origin of neurodegenerative diseases including aging, tumor, and stroke. These novel MSI techniques for elements and isotopes have been developed with the use of a powerful ICP-MS system combined with collision cell technology. Since the implementation of this technology, the BrainMet Centre has realized considerable benefits, such as accuracy, reliability, reproducibility of results, and increased sample throughput.
Founded in December 2009, the Analytical BrainMet Competence Centre was opened in collaboration with Thermo Fisher Scientific (Bremen, Germany) to create new and powerful MSI technologies for dementia research. This cutting-edge research aims to advance understanding of dementia by studying the effects of metals and metalloproteins in the origin of neurodegenerative diseases such as Alzheimer’s, Parkinson’s, epilepsy, as well as their effects on aging of the brain and in brain lesions.
In most neurodegenerative diseases, abnormal accumulations of metals are observed in the brain, leading to the destruction of the neural network and, subsequently, cell death. Analysts at the BrainMet Centre are researching the specific quantitative distribution of essential and toxic metals in thin native tissue sections of the brain to study their significance in the occurrence of diseases of the central nervous system (CNS).
Metals imaging and analysis of metalloproteins
As essential mineral elements, metals are of preeminent significance for living organisms and are vital for brain biochemistry and cellular processes. In most neurodegenerative diseases, abnormal deposition of metals is observed in certain brain regions. For example, in the case of Parkinson’s disease, the iron content of the cells in the substantia nigra region of the brain is known to increase, leading to the destruction of nerve cells.
Prior to the establishment of the BrainMet Centre, no studies had been performed on the quantitative distribution of metals (imaging) combined with the analysis of metalloproteins in tissue samples of diseased brain compared to controls. The BrainMet Centre aims to develop robust, reproducible, reliable, sensitive, and precise BrainMet techniques and use them to research the quantitative distribution of all essential and toxic metals, nonmetals (e.g., carbon, phosphorus, sulfur, chlorine, and iodine) and metalloids (e.g,, arsenic, selenium, and antimony). ICP-MS and LA-ICP-MS have been established as the most sensitive inorganic/bioinorganic analytical techniques for the determination of trace elements and isotope ratios. LA-ICP-MS has also proven to be a strong technique for quantitative elemental imaging of biological tissue including soft and hard animal tissue, plants, bones, teeth, hair, and nails. In addition, the method is able to detect metals, phosphorus, and sulfur in protein spots. The BrainMet Centre began working to develop novel analytical techniques involving LA-ICP-MS technology capable of providing validated and plausible distribution images of all metals, metalloids, and selected nonmetals in rodent and human brain tissue.
Bioimaging of elements and single-cell analysis
Figure 1 - XSERIES 2 ICP-MS system.
To conduct its challenging research and develop innovative bioimaging techniques, the BrainMet Centre required an instrument with the ability to provide a high level of sensitivity and productivity for both routine and high-performance analytical work. The BrainMet Centre implemented the Thermo Scientific XSERIES 2 ICP-MS system (Thermo Fisher Scientific) (Figure 1), which combines third-generation collision cell and protective ion extraction technologies with an ergonomic, compact design.
By using the ICP-MS system combined with laser ablation (LA-ICP-MS), the BrainMet Centre has been able to develop techniques for bioimaging of elements. The methods include new quantification strategies using synthetic matrix-matched brain standards and on-line solution-based calibration methods for bioimaging of brain tissue and biomonitoring of metals in single hairs. This enables the monitoring of platinum in a single hair after cisplatin treatment for cancer.
Recently, a new metal-protein microscope (MPM) was created by coupling a laser microdissection (LMD) apparatus and the ICP-MS system. This breakthrough approach enables a new dimension of BrainMet techniques (with spatial resolution at submicrometer scale) in single-cell analysis combined with fluorescence and proteomics studies.
Bioimaging of metals in brain tissue
The novel analytical technique based on the use of LA-ICP-MS technology has proven to be highly efficient for the quantitative bioimaging of metals in samples of brain tissue. The team at BrainMet has been able to take advantage of the features offered by the ICP-MS system, which include multielemental capability, low detection limits, high-precision isotope ratio measurements, and increased sample throughput. Using the technique, the team has been able to conduct routine measurements of brain tissue, enabling the development of new quantification procedures by solution-based calibration.
There has also been a significant increase in the reliability and accuracy of the data obtained by the Centre, while the collision cell technology incorporated as standard in the instrument has allowed them to overcome the matrix effects and interference problems of atomic and polyatomic ions inherent in ICP-MS technology. As a result, in bioimaging LA-ICP-MS applications involving the use of the ICP-MS technology, interference problems such as those caused by oxide ions have practically been eliminated, permitting elements such as iron, sulfur, and phosphorus to be measured more easily.
Figure 2 - Applications of BrainMet techniques.
Following the deployment of the new ICP-MS system at the BrainMet Centre, the instrument has been used successfully in selected studies for the quantitative distribution analysis of healthy and diseased samples of brain tissue. Studies have included cases of Parkinson’s disease mouse brain studies, photo-induced stroke, and depression, as well as for investigating the growth of brain tumors. The technique can also be used for routine examinations of normal tissue samples for brain research while also being applicable for micro- and nanoelectronics. The analytical protocols and different applications are described in the handbook, Inorganic Mass Spectrometry, Principles and Applications, by J.S. Becker (Wiley 2007). Several applications of novel BrainMet techniques are also summarized in Figure 2.
Applications in forensics and materials research
The BrainMet Centre is also applying LA-ICP-MS technology for the direct analysis of solid samples such as provenance of sample, forensics, and materials research. The Centre has recently used the system to analyze a gold wedding ring from the Middle Ages in respect to its matrix composition (fingerprinting). The high sensitivity of ICP-MS means that only three laser shots were necessary to characterize the composition of the gold ring with regard to its origin. Further applications for which the instrument is being used include analysis of metal distribution in 1-D and 2-D gels, trace analysis, and determination of stoichiometry of solid materials by LA-ICP-MS, depth profiling, and imaging of solid surfaces.
Through its research, the BrainMet Centre has established that by combining its studies on the bioimaging of metals with those of metallomics, it is possible to explore the relationship between metal ions and metalloproteins in brain tissue and neurodegenerative diseases. To achieve its goals, the laboratory required a LA-ICP-MS solution that was capable of providing validated images of all metals, metalloids, and selected nonmetals in brain tissue.
Since the implementation of the new ICP-MS system, the BrainMet Centre has benefitted from a robust, sensitive, accurate, and reliable system that optimizes the laboratory’s performance. The resulting data from the studies have been successfully combined by the BrainMet Centre with neuroscientific imaging procedures from the Institute of Neurosciences and Medicine at the Forschungszentrum Jülich. These procedures include positron emission tomography (PET), autoradiography, magnetic resonance imaging (MRI), and histochemical and optical imaging techniques to enable high-tech biomedical research.
The BrainMet Centre’s techniques are currently being further refined with the aim of improving the lateral resolution down to the low micrometer and nanometer range. In addition, the development of the metal-protein microscopy (MPM) will also make distribution analyses on individual cells, cell organelles (e.g., mitochondria), and synapses possible in the future.
Dr. Sabine Becker is Head of the Analytical BrainMet Center, Forschungszentrum Jülich, Germany. Dr. Hamester is Product Manager, ICP-MS/GD-MS, Thermo Fisher Scientific, Hanna-Kunath-Strasse 11 28199, 0421 Bremen, Germany; tel.: 800-532-4752; e-mail: email@example.com.