Centrifuge-free cell radiolabeling using acoustophoresis

Tracking ex vivo radiolabeled cells using radionuclide imaging such as positron emission tomography is an emerging method for evaluating cell-based therapies. Traditional radiolabeling requires a centrifuge in multiple steps to optimize labeling and remove unbound radiotracers. With the goal of automating the radiolabeling procedure, we explored an acoustophoresis-based approach for radiolabeling cells, eliminating the need of using a centrifuge, simplifying the design of this future device. The AcouWash 2 (AcouSort AB, Lund, Sweden), an acoustophoresis based cell washing device, was evaluated for its ability to label EL4 murine T lymphoblasts with zirconium-89 (⁸⁹Zr)-oxine without centrifugation. The AcouWash 2 successfully replaced the culture medium with a protein-free buffer, as required for ⁸⁹Zr-oxine cell labeling. Additionally, it was able to concentrate EL4 cells by a factor of 5.6 ± 0.4, achieving or exceeding the optimal labeling cell density. After cell incubation with ⁸⁹Zr-oxine, AcouWash 2 exchanged the incubation solution with a solution for infusion, removing unbound ⁸⁹Zr-oxine. These steps eliminated the need for centrifugation at each stage of the labeling procedure. The resulting radiolabeled EL4 cells exhibited labeling metrics, specific activity, percent labeling efficiency, percent free ⁸⁹Zr-oxine in the suspension buffer and cell viability, comparable to those obtained from conventional centrifuge-based method. Our results demonstrate that the radiolabeling can be performed entirely using acoustophoresis, which paves the way for developing a fully automated radiolabeling device based on acoustophoresis technology.