CAR-T Expansion Monitoring: Consolidated Cell Characterization Using Moxi GO II

CAR-T expansion QC has long leaned on two separate core-lab instruments — a Coulter counter for counting and sizing, and a multi-parameter flow cytometer for viability and immunophenotyping — whose 3–6 hour turnaround can arrive after the intervention window has closed; this University of Pennsylvania study (Pajarillo et al., Cytotherapy 2024) shows the Moxi GO II consolidating both into a single 15-second, at-bench measurement.

Working at the University of Pennsylvania Center for Cellular Immunotherapies (Ruella Lab), the authors benchmarked the Moxi GO II — a compact, battery-powered instrument that pairs Coulter-principle volumetric sizing with 2-color fluorescence detection — against the gold-standard two-instrument workflow (a Beckman Coulter Multisizer and a BD LSRFortessa) across routine CAR-T expansion assays. From 60 µL of stained sample, a single 15-second test returns cell count, size, viability, and CD4/CD8 and CAR19 phenotyping, matching the reference instruments for viability (r² = 0.97), CD4+ T cell identification (r² = 0.997), and CAR19 transduction efficiency (r² = 0.90). The note also states plainly where the instrument fits — the routine 2-color checkpoints that make up most of an expansion campaign — and where high-parameter flow cytometry is still the right tool.

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• Two instruments consolidated into one 15-second test — the Moxi GO II combines Coulter-principle counting and sizing with 2-color fluorescence viability and immunophenotyping in a single at-bench measurement from 60 µL of sample, replacing the standard workflow of a separate Coulter counter plus a multi-parameter flow cytometer.
• The 3–6 hour core-lab turnaround eliminated — routine expansion checkpoints no longer wait on dual core-instrument scheduling, sample transport, and cytometrist availability; actionable QC data arrives at the bench at the moment expansion decisions are being made.
• Viability matched the flow cytometer at r² = 0.97 — the Moxi GO II's Coulter-based viability assessment correlated at r² = 0.97 (P < 0.0001) with the multi-parameter flow cytometer reference across the clinically relevant viability range.
• CD4+ T cell identification at r² = 0.997 — near-perfect concordance with the flow cytometer on the CD4/CD8 ratio, a primary process QC metric used to inform re-stimulation timing and harvest readiness.
• CAR19 transduction efficiency at r² = 0.90 — CAR construct expression, a measurement that previously required dedicated flow-cytometry core access, tracked at r² = 0.90 with the reference instrument.
• Absolute cell-size tracking of activation state — Coulter-principle sizing measures each cell's true displaced volume (~4% CV) rather than an optical Forward-Scatter estimate, giving a real-time readout of the femtoliter-scale T cell swelling that signals activation during expansion.
• Scope reported honestly — the Moxi GO II is optimized for routine 2-color process QC (CD4/CD8, viability, concentration, and size); labs needing 8+ simultaneous markers, multi-laser excitation, or rare-event detection should continue to use high-parameter flow cytometry for those specific experiments.