Powerful EM analysis provides images and quantitative data on virus integrity and purity

Gene therapy / Viral and VLP based vaccines

A fundamental challenge in manufacturing virus-based products is achieving sufficient purity while maintaining virus integrity. TEM is a direct visual method that provides high-resolution morphology information on viruses and their associated impurities.

For viral characterization, Vironova services offer a complete EM analysis package that includes both negative stain transmission electron microscopy and cryo-transmission electron microscopy.  Each of these methods provides powerful image datasets representative of the sample and a report that highlights the sample morphology with a graphical presentation of quantitative data and conclusions from the analysis. 

In addition to our TEM services, we also offer MiniTEM – a movable 25kV TEM microscope with a high level of automation and ~1nm resolution. MiniTEM allows a user-friendly electron microscopy technology for viral characterization to be put in the hands of any process developer in the gene therapy or vaccine field.

With MiniTEM you can carry out automated viral characterization studies in your own lab, close to your process.

Choose your analysis

Size distribution analysis
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MiniTEM automates imaging, AAV particle detection and measurements to present accurate size distribution data

MiniTEM™ can reveal contaminants in AAV samples, for example proteosomes in the figure below.


In the above graph an overlay of the results from MiniTEM and DLS analysis of the same sample is shown. DLS was in this case not able to distinguish between AAV particles and the proteasomes.

Size distribution study with MiniTEM can also reveal small size debris and aggregates

Level and size of aggregates

The size distribution graph shows the number of particles of expected size as well as smaller size debris and aggregates – the data is easily correlated to what is revealed in the acquired images.

Purity analysis
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Automated size distribution analysis can be used to detect level of debris and compare the purity of different AAV samples

Level of debris

The box-plot shows purity measurement of the two samples calculated as the ratio of the total area of debris to Adenovirus particles.

Virus integrity status
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MiniTEM can be used to automatically quantify disrupted empty AAV particles

Virus particle morphology

TEM analysis of negatively stained AAV samples (nsTEM) is a reproducible method for revealing particles with disrupted capsid structure. Disrupted particles take in stain and can therefore be identified by their darker centres. 


Comparing particle integrity of two AAV samples in MiniTEM:

Integrity graphs

Integrity states


Comparing particle integrity of Adenovirus samples in MiniTEM:

Integrity ratio


Below is an analysis of MuLV (murine leukemia virus). The numbers of circular intact particles with preserved morphology, of non-circular particles morphologically affected by the processing, and of debris, are compared.

MuLV debris

Detailed virus morphology
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Examples of details in virus morphology revealed with nsTEM


Virus integrity before Virus integrity after
Rotavirus Influenza


Influenza spike proteins

Influenza virus protein


Percentage full AAV capsids
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The VAS software in combination with cryoTEM accurately distinguishes between full and empty AAV particles

Cryo EM Cryo EM graph

The output of VAS analysis is a report with quantitative data.


Cryo EM table


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Sample: Myoviridae Coliphage - Isolated by the Brouns lab, Kavli Institute - BN/TU Delft

These analyses are part of our standard service offering. If you’d rather have your own automated solution – take a closer look at our MiniTEM system

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