Cell identity, count, and viability for critical quality attributes using the Cellaca® PLX image cytometer

Carolina Franco Nitta, Mackenzie Pierce, Tim Smith, Marek Dobrowolski,
Srinivas Gundimeda, Bo Lin, Dmitry Kuksin, and Leo Li-Ying Chan

Cell and Gene therapy is one of the fastest growing fields of cancer
therapeutics that heavily relies on robust and consistent
instrumentations and technologies to verify and validate fit-for purpose critical quality attributes (CQA). Some of the key
parameters required for satisfying CMC (Chemistry Manufacturing
and Controls) criteria standards for cellular therapeutic products are
cell identity, count, viability, purity, potency, stability, and
microbiological quality, which may be routinely performed using
flow cytometry. Some of these critical attributes can be exceedingly
trivial for flow cytometric analysis, which can be complex, requires a
dedicated user, and may carry a high maintenance cost. In the past
decade, affordable image cytometry has been developed for cell
characterization and cell-based assays but has not demonstrated the
sensitivity required for visualization and analysis of surface markers,
cell health, and viability. In this work, we demonstrate the capability
of the newly developed Cellaca® PLX image cytometry system for
population analysis of surface markers, viability of fluorescent
protein-expressing cells, and cell health in comparison to flow
cytometry. For immunophenotyping assays, PBMCs were stained
with anti-human CD3/CD4/CD8 antibodies with Hoechst.
Additionally, viability detection of GFP and RFP-containing cell lines
was performed by staining with RubyDead and Hoechst. Finally,
apoptosis was induced in Jurkat cells with Staurosporine and stained
with Caspase 3-488, RubyDead, and Hoechst. All assays were
imaged and analyzed using the Cellaca® PLX image cytometer, and
the data generated were compared directly to the CytoFlex flow
cytometer. Results show similar percentages of surface marker
populations: CD3 (76% and 81%, PLX and CytoFlex, respectively),
CD4 (43% and 42%), and CD8 (15% and 17%). RFP and GFPcontaining cells showed comparable viabilities on Cellaca® PLX and
CytoFlex, and the population percentages of Hoechst positive cells
stained with Caspase 3 and RubyDead were within 5% of each other.
Our experiments demonstrate that the Cellaca® PLX can be of
significant value to the Cell and Gene Therapy communities by
providing novel image cytometry methods which may satisfy several
CMC criteria including high throughput capabilities with sensitivity
and low maintenance.