Cytoprotective Encapsulation of Individual Jurkat T Cells within Durable TiO₂ Shells for T‐Cell Therapy

Lymphocytes, such as T cells and natural killer (NK) cells, have therapeutic promise in adoptive cell transfer (ACT) therapy, where the cells are activated and expanded in vitro and then infused into a patient. However, the in vitro preservation of labile lymphocytes during transfer, manipulation, and storage has been one of the bottlenecks in the development and commercialization of therapeutic lymphocytes. Herein, we suggest a cell‐in‐shell (or artificial spore) strategy to enhance the cell viability in the practical settings, while maintaining biological activities for therapeutic efficacy. A durable titanium oxide (TiO 2 ) shell is formed on individual Jurkat T cells, and the CD3 and other antigens on cell surfaces remain accessible to the antibodies. Interleukin‐2 (IL‐2) secretion is also not hampered by the shell formation. This work suggests a chemical toolbox for effectively preserving lymphocytes in vitro and developing the lymphocyte‐based cancer immunotherapy.