Groundbreaking imaging tech maps elements in frozen bio-particles with precision
Flash-freezing samples preserves their structure in a state close to how they exist in nature.
Researchers have used this technique for years to study the size, shape, and dispersion of biological matter at high resolution.
But cryo-TEM has one major blind spot: it struggles to reveal elemental composition, an essential factor for understanding material function.
Current solutions like energy-filtered TEM (EF-TEM) and electron energy loss spectroscopy (EELS) can detect elemental signals, but they come with drawbacks.
They often cause sample damage, suffer from image drift, and have mostly been used for metals or bulk materials.
Imaging beyond the structure
A team at Tohoku University has now solved that limitation. They developed a new cryo-EELS/EF-TEM technique that captures both the structure and elemental makeup of samples in frozen solvents.
The method allows researchers to study delicate organic nanomaterials without compromising image clarity or damaging the sample.
The problem with conventional EELS imaging is two-fold: ice within the sample increases unwanted background signals, and drift during scanning causes blurred images.
These issues make it hard to resolve the actual material under investigation, especially in biological or soft organic samples.
To address this, the Tohoku team refined the '3-window method,' a known EELS background correction approach, tailoring it for frozen conditions.
This improved background subtraction helps remove interference from the ice, making the elemental signals from the target material stand out clearly.
Solving drift with new tools
Drift remained a challenge during long EELS scans. To counter this, the team introduced a drift compensation system that stabilizes the image throughout data collection.
They also developed a software extension for the ParallEM microscope control system. This tool automates energy shift adjustments during elemental mapping, streamlining the process.
With the new method in place, the researchers successfully visualized silicon distribution in silica nanoparticles as small as 10 nanometers.
The particles were suspended in frozen solvent, closely mimicking real-world biological conditions.
They also tested the technique on hydroxyapatite particles, a calcium phosphate material found in bones and teeth.
The method clearly revealed the distribution of calcium and phosphorus, two biologically significant elements, alongside the particles' structure.
The ability to map both structure and composition at such fine resolution opens up major possibilities.
This technique can now support research into biomaterials, medical implants, food technology, catalysts, and even functional inks.
The findings were published in Analytical Chemistry on July 31, 2025.
By overcoming the core limitations of cryo-EELS and EF-TEM, namely drift, damage, and background noise, the Tohoku University team has pushed the boundaries of what cryo-TEM can do.
Researchers across disciplines now have a powerful new tool to explore nanoscale materials' hidden chemistry without losing the detail or integrity of their samples.
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