Extracellular Silica Nanomatrices Promote In Vitro Maturation of Anti‐tumor Dendritic Cells via Activation of Focal Adhesion Kinase

The efficacy of dendritic cell (DC)-based cancer vaccines is critically determined by the functionalities of in vitro maturated DCs. The maturation of DCs typically relies on chemicals that are cytotoxic or hinder the ability of DCs to efficiently activate the antigen-specific cytotoxic T-lymphocytes (CTLs) against tumors. Herein, the maturation chemicals are replaced with extracellular silica nanomatrices, fabricated by glancing angle deposition, to promote in vitro maturation of murine bone marrow-derived DCs (mBMDCs). The extracellular nanomatrices composed of silica nanozigzags (NZs) enable the generation of mature mBMDCs with upregulated levels of co-stimulatory molecules, C-C chemokine receptor type-7, X-C motif chemokine recetpor-1, DC-specific ICAM-3 grabbing nonintegrin, and enhanced endocytic capacity. The in vitro maturation is partially governed by focal adhesion kinase (FAK) that is mechanically activated in the curved cell adhesions formed at the DC-NZ interfaces. The NZ-maturated mBMDCs can prime the antigen-specific CTLs into programmed cell death protein-1 (PD-1)^lowCD44^high memory phenotypes in vitro and suppress the growth of tumors in vivo. Meanwhile, the NZ-mediated beneficial effects are also observed in human monocyte-derived DCs. This work demonstrates that the silica NZs promote the anti-tumor capacity of in vitro maturated DCs via the mechanoactivation of FAK, supporting the potential of silica NZs being a promising biomaterial for cancer immunotherapy.