Bulk Harvest Testing (QnsTEM)
GMP-Validated Viral Safety and Particle Quantification in Complex Biological Matrices
Bulk harvest testing using Quantitative Negative Staining Transmission Electron Microscopy (QnsTEM) enables the direct detection, characterization, and quantification of viral particles and virus-like particles (VLPs) in cell-free bioprocess samples.
It is specifically designed for highly complex and variable biological matrices encountered in upstream and downstream biopharmaceutical manufacturing, including cell culture supernatants, clarified harvests, and process intermediates.
Unlike targeted molecular assays, QnsTEM provides morphology-based, non-targeted detection of known and unknown viral agents, making it a powerful orthogonal method for viral safety assessment.
Why QnsTEM for Bulk Harvest Testing?
Bulk harvest samples present significant analytical challenges due to:
- High variability between production runs
- Complex protein and impurity backgrounds
- Presence of cellular debris and aggregates
- Matrix effects that can impact assay performance
QnsTEM is specifically engineered to remain robust across diverse sample matrices, enabling reliable detection and quantification even in challenging bioprocess conditions.
Key advantages for bulk harvest applications include:
- High tolerance to complex biological matrices
- Consistent performance across upstream and downstream samples
- Direct visualization without reliance on target-specific reagents
- Reliable detection of low-abundance viral particles
Applications
- Adventitious agent testing of bulk harvest samples
- Viral particle quantification in process intermediates
- Retrovirus-like particle (RVLP) detection
- Contamination investigations and root-cause analysis
- Upstream and downstream process monitoring
- Orthogonal viral safety testing
Our state-of-the-art method of QnsTEM for the detection of adventitious agents in unprocessed bulk harvest samples
Method
After separating the cells from the test item via centrifugation, possible virus or virus-like particles can be concentrated in the supernatant by ultracentrifugation. A defined volume of this test item is then stained with heavy metal salts. Biological structures are embedded in the staining agent and not directly stained (negative staining). These structures then appear bright against a dark background when visualising with TEM.
Quantitative Negative Staining TEM (QnsTEM) is an improved approach designed
to enhance the sensitivity, accuracy and robustness of virus detection and quantification in
biological suspensions. QnsTEM eliminates the need to mix beads into the sample by utilizing
reference grids for calibration, thereby reducing variability and improving reproducibility. The
method provides a state of the art and more reliable alternative to existing TEM
based techniques for adventitious agent detection in bulk harvest samples and for the
qualitative investigation of particles. The QnsTEM method enables accurate and precise
quantification of virus particles by transmission electron microscopy using a validated
calibration approach, which has been validated using well characterized virus reference materials with titers determined by qPCR.
to enhance the sensitivity, accuracy and robustness of virus detection and quantification in
biological suspensions. QnsTEM eliminates the need to mix beads into the sample by utilizing
reference grids for calibration, thereby reducing variability and improving reproducibility. The
method provides a state of the art and more reliable alternative to existing TEM
based techniques for adventitious agent detection in bulk harvest samples and for the
qualitative investigation of particles. The QnsTEM method enables accurate and precise
quantification of virus particles by transmission electron microscopy using a validated
calibration approach, which has been validated using well characterized virus reference materials with titers determined by qPCR.
To ensure that the test is executed in the defined parameters of the validation, system suitability criteria (SSC) were defined. Only after all SSCs have been successfully passed, the test item grid is then screened for adventitious agents.
Turnaround Time
Results and the corresponding Final Reports (CoA) can be issued within 5 working days.