Uranium-free X solution: a new generation contrast agent for biological samples ultrastructure.

Area of Science:

• Electron Microscopy
• Materials Science
• Biotechnology

Background:

• Biological samples have low atomic number elements, resulting in poor electron scattering and minimal contrast in Transmission Electron Microscopy (TEM).
• Standard embedding resins used for thin sectioning also consist of light atoms, further reducing contrast between the sample and its surroundings.
• Heavy metal salt staining solutions, particularly uranyl acetate (UA), are commonly used to enhance contrast, but alternatives are sought due to UA's radiogenic issues.

Purpose of the Study:

• To develop and characterize a novel staining solution using lanthanide polyoxometalates (LnPOMs) as a heavy atom source for TEM.
• To evaluate the efficacy of this new solution (X Solution or X SOL) as an alternative to uranyl acetate for various biological sample preparation techniques.
• To demonstrate that the proposed LnPOM-based solution achieves comparable or superior staining performance to UA.

Main Methods:

• Formulation of a novel staining solution (X Solution) utilizing lanthanide polyoxometalates (LnPOMs).
• Application of X Solution for negative staining (NS), en bloc staining, and post sectioning staining (PSS) of biological samples.
• Extensive chemical characterization of the LnPOM species within the X Solution.
• Comparative analysis of staining efficiency against uranyl acetate (UA).

Main Results:

• The developed X Solution, based on LnPOMs, effectively enhances contrast in biological samples for TEM analysis.
• X Solution demonstrated remarkable performance in NS, en bloc, and PSS applications.
• The staining efficiency of X Solution was found to be superior to that of uranyl acetate (UA).

Conclusions:

• Lanthanide polyoxometalates (LnPOMs) provide a viable and effective heavy atom source for biological sample staining in TEM.
• The proposed X Solution serves as a high-performance alternative to uranyl acetate (UA) for multiple staining techniques.
• This new staining approach offers improved contrast and performance, addressing limitations associated with traditional methods.