Oxygen‐Generating Cryogels Restore T Cell Mediated Cytotoxicity in Hypoxic Tumors

Abstract

Solid tumors are protected from antitumor immune responses due to their hypoxic microenvironments. Weakening hypoxia‐driven immunosuppression by hyperoxic breathing of 60% oxygen has shown to be effective in unleashing antitumor immune cells against solid tumors. However, efficacy of systemic oxygenation is limited against solid tumors outside of lungs and has been associated with unwanted side effects. As a result, it is essential to develop targeted oxygenation alternatives to weaken tumor hypoxia as novel approaches to restore immune responses against cancer. Herein, injectable oxygen‐generating cryogels (O2‐cryogels) to reverse tumor‐induced hypoxia are reported. These macroporous biomaterials are designed to locally deliver oxygen, inhibit the expression of hypoxia‐inducible genes in hypoxic melanoma cells, and reduce the accumulation of immunosuppressive extracellular adenosine. The data show that O2‐cryogels enhance T cell‐mediated secretion of cytotoxic proteins, restoring the killing ability of tumor‐specific cytotoxic T lymphocytes, both in vitro and in vivo. In summary, O2‐cryogels provide a unique and safe platform to supply oxygen as a coadjuvant in hypoxic tumors and have the potential to improve cancer immunotherapies.

Biomaterials and Oxygen Join Forces to Shape the Immune Response and Boost COVID‐19 Vaccines

“…The capacity of O 2 ‐cryogels to reduce local hypoxia was first evaluated. O 2 ‐cryogels and cryogels were fabricated as previously described, [ 32 ] and their ability to generate oxygen in vitro was confirmed using contactless environmental oxygen probes (Figure S1, Supporting Information). As intended, O 2 ‐cryogels released oxygen in their surrounding environment for nearly 48 h, with an oxygen level peaking at over 310 µM after 3 h. On the contrary, catalase‐free O 2 ‐cryogels produced an insignificant amount of oxygen, confirming the need to use this enzyme.…”

“…For O 2 ‐cryogel fabrication, APC (1% w/v, Sigma‐Aldrich), and CaO 2 (1% w/v) were mixed with the cryogel polymer solution before the addition of TEMED and APS as previously reported. [ 32 ]…”

“…Cryogel Fabrication: Cryogels were fabricated as previously described by redox-induced free radical cryopolymerization of hyaluronic acid glycidyl methacrylate (HAGM, 4% w/v) at subzero temperature (−20 °C). [16,26,32] Briefly, the polymer solution was precooled at 4 °C prior to adding tetramethylethylenediamine (TEMED, 0.42% w/v, Sigma-Aldrich) and ammonium persulfate (APS, 0.84% w/v, Sigma-Aldrich). Then, the mixture was transferred into Teflon molds (4 mm × 4 mm × 1 mm, cubiform with 2 square-shaped sides), placed in a freezer at −20 °C, and allowed to cryopolymerize for 16 h. Finally, the newly formed cryogels were thawed at room temperature (RT) to remove ice crystals and washed with Dulbecco's PBS (Gibco).…”

“…[26] This is supported with our previous findings on cryogel cancer vaccines where a sustained release of immunomodulatory factors (GM-CSF and CpG ODN 1826) promoted DC infiltration and stimulation. [26,32,33] Within the cryogels, DCs are expected to take up N and RBD protein antigens and be simultaneously stimulated by CpG ODN 1826 and additive oxygen. Activated, antigen-loaded DCs would then migrate to the draining LNs, activate antigen-specific T cells, and ultimately boost antibody-producing B cells.…”

“…[ 31 ] Thus, oxygen‐producing calcium peroxide (CaO 2 ) particles and acrylate‐PEG‐catalase (APC) were incorporated within the cryogel‐based vaccine formulations before freezing, as previously described. [ 32 ] The resulting oxygen‐generating COVID‐19 cryogel‐based vaccine (O 2 ‐Cryogel VAX ) was designed to generate oxygen upon the reaction of CaO 2 with water and to eliminate hydrogen peroxide byproducts through a catalase‐mediated breakdown. Herein, we first characterized the encapsulation and release of biomolecules from O 2 ‐Cryogel VAX and their potential to reverse hypoxia‐associated DC inhibition.…”