TABLE 3.

Overview of studies reporting immune cell infiltration using biomaterial-based scaffolds for (CAR-)T cell adoptive cell transfer. The table gives an overview of different materials used for ACT of T cells and provides details about the mouse model used, the presence of a fibrotic capsule, the immune cell infiltration, long term stability and biocompatibility, and the delivery route tested.

Biomaterial	Mouse model	Fibrotic capsule	Immune cell infiltration	Long term stability	Long term biocompatibility	Delivery route	Ref
HA cryogel—1, 5, and 10 days	Immunocompetent (C57BL/6J)	N.A.	Day 10, mainly neutrophils (>80%, 6.5∙106 cells), some macrophages (<5%, 2.5∙104)	Short, average half-life 9.5 days	N.A.	Injection s.c. with 16G needle	Kerr et al. (2022)
	Immunodeficient (NSG)	N.A.	Day 10, mainly macrophages (90%, 3∙104), very little neutrophils	Long, average half-life >3 months
Nitinol film—4 months	Female NSG	Thin layer—4 months	Limited (macrophages, lymphocytes and multinucleate giant cells)	Yes, material is non-degradable	Yes, no changes in ALT, AST, LDH or CRE	Implanted	Coon et al. (2020)
Alginate Histopathology at 4 weeks Immune cell infiltration at day 4	Immune competent (C57BL/6J) for histopathology study. NSG mouse engrafted with human PBMCs for immune cell infiltration study	Thin layer—4 weeks	Limited at day 4, mainly murine CD11b+ (80% of all infiltrating cells)	Yes, material is non-degradable	Yes, no histopathology of the major organs at 4 weeks. Blood biochemical analysis was fine	Implanted	Agarwalla et al. (2022)
PNP hydrogel—4 weeks	Immune competent (SKH1-Elite), for biocompatibility study	No visible sign	N.A.	Short, retention half-life of 8.9 ± 2.6 days	N.A.	Injected s.c. 21G needle	Grosskopf et al. (2022)