T cell therapies have shown limited success in solid tumors, mainly due to the difficulty of T cells to penetrate the tumor tissue. Here, we develop injectable and viscoelastic click alginate hydrogels for local and sustained delivery of T cells, with the goal to improve T cell administration, viability, proliferation, and persistence in vivo . Oxidized alginate (Alg), functionalized with norbornene-to-tetrazine for inverse electron demand Diels-Alder covalent click crosslinking, and varying low (1% Alg) and high (2% Alg) alginate concentration were used. 1% Alg hydrogels showed better injectability in a fully crosslinked state, characterized by lower stiffness, larger mesh size, viscoelastic behavior, lower injection forces and higher cell viability upon injection. In vitro experiments demonstrated that 1% Alg supported T cell viability and proliferation, and promoted sustained release for 10 days. Using a chicken in vivo chorioallantoic membrane model, hydrogel-based T cell administration exhibited better local delivery, proliferation and persistence over time compared to bolus injection, with 1% Alg showing enhanced T cell release compared to 2% Alg. Further, in a murine model with a local injection in the mammary gland, 1% Alg showed enhanced T cell persistence within the mammary gland and high tissue integration. In conclusion, we engineered injectable, viscoelastic click alginate hydrogels that support T cell administration, local injection, viability, proliferation and persistence in vivo, opening future opportunities for spatio-temporal control of T cell immunotherapies. • By modulating the polymer concentration and crosslinking density, it is possible to control the injectability and viscoelasticity of click crosslinked alginate hydrogels. Lowering the alginate concentration, enhances viscous relaxation. • Lower alginate concentration supports higher T cell viability, proliferation and promotes sustained T cell release in vitro. • Injectable click crosslinked alginate hydrogels enable T cell transplantation and persistence in vivo. • Hydrogel-based T cell administration exhibited better local delivery and persistence over time compared to bolus injection in an in vivo CAM model. • Lower alginate concentration showed enhanced T cell persistence and high tissue integration within the mammary gland in a in vivo mouse model.
Berasain et al. (Wed,) studied this question.