Serafini, C. E.; Gorti, V.; Casteleiro Costa, P.; Silva Trenkle, A. D.; Kanwar, B.; Wang, B.; Wicker, B.; Kippner, L. E.; LeCompte, I.; Chen, R. Q.; Joffe, B.; Li, Y.; Bowles-Welch, A. C.; Li, J.; Brown, C. E.; Kwong, G. A.; Balakirsky, S.; Roy, K.; Robles, F. E.

Cell therapies, including T cell immunotherapies, offer promising treatments for previously untreatable diseases, but their widespread use is hindered by challenges in monitoring therapeutic cells during culture--impacting consistency, potency, and cost. This work demonstrates the use of quantitative phase imaging (QPI), specifically a compact, non-interferometric form called quantitative oblique back illumination microscopy (qOBM), for non-destructive, label-free, in-line assessment of T cell cultures. qOBM enables near real-time feedback on culture growth, contamination, and cell status (viability and activation), comparable to flow cytometry. We further apply this method to characterize genetically modified CAR T cells and explore its potential for advanced T cell phenotyping. Analysis of data from over 50 independent donors shows strong correlation between qOBM metrics and traditional destructive at-line assays. Overall, qOBM provides a powerful tool for continuous, in-line monitoring of therapeutic cell cultures, which can be transformative for improving reproducibility, reducing costs, and advancing the development of cell-based therapies.