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Published on: June 28, 2019
Hafnium-Substituted Wells-Dawson Polyoxometalate as a High-Performance Contrast Agent for Transmission Electron
Aleksandra Milosavljević1, Mila Ćetković1, Tamara Kravić-Stevović1
1Institute of Histology and Embryology, Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia.
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Transmission electron microscopy (TEM) is a key tool for ultrastructural analysis, yet its performance critically depends on contrast agents, many of which are constrained by toxicity and regulatory concerns. In this study, Wells-Dawson (WD)-type polyoxometalates (POMs), including Parent WD-POM, Lacunary WD-POM, Zr-WD 1:2 POM, and Hf-WD 1:2 POM, were investigated as alternative contrast agents for TEM imaging of rat kidney tissue. Among the tested compounds, Hf-WD 1:2 POM provided the most consistent contrast enhancement, enabling clear visualization of subcellular structures with minimal background interference and no detectable aggregation. Its contrast performance depended on both concentration and incubation time, with higher concentration (0.01 mol/L) and prolonged incubation (24 h) yielding increased signal-to-noise ratio (SNR), although SNR alone did not fully reflect image quality. In comparison with conventional staining agents (uranyl acetate and Uranyless), Hf-WD 1:2 POM achieved significantly improved contrast effectiveness without inducing detectable tissue damage. These findings identify Hf-WD 1:2 POM as a promising non-radioactive alternative for TEM imaging and support the potential of POMs as versatile platforms for the development of advanced contrast agents.
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01:15Transmission Electron Microscopy
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When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
01:20Preparation of Samples for Electron Microscopy