NK cells encapsulated in micro/macropore-forming hydrogels via 3D bioprinting for tumor immunotherapy

Abstract

Background Patients face a serious threat if a solid tumor leaves behind partial residuals or cannot be completely removed after surgical resection. Immunotherapy has attracted attention as a method to prevent this condition. However, the conventional immunotherapy method targeting solid tumors, that is, intravenous injection, has limitations in homing in on the tumor and in vivo expansion and has not shown effective clinical results. Method To overcome these limitations, NK cells (Natural killer cells) were encapsulated in micro/macropore-forming hydrogels using 3D bioprinting to target solid tumors. Sodium alginate and gelatin were used to prepare micro-macroporous hydrogels. The gelatin contained in the alginate hydrogel was removed because of the thermal sensitivity of the gelatin, which can generate interconnected micropores where the gelatin was released. Therefore, macropores can be formed through bioprinting and micropores can be formed using thermally sensitive gelatin to make macroporous hydrogels. Results It was confirmed that intentionally formed micropores could help NK cells to aggregate easily, which enhances cell viability, lysis activity, and cytokine release. Macropores can be formed using 3D bioprinting, which enables NK cells to receive the essential elements. We also characterized the functionality of NK 92 and zEGFR-CAR-NK cells in the pore-forming hydrogel. The antitumor effects on leukemia and solid tumors were investigated using an in vitro model. Conclusion We demonstrated that the hydrogel encapsulating NK cells created an appropriate micro–macro environment for clinical applications of NK cell therapy for both leukemia and solid tumors via 3D bioprinting. 3D bioprinting makes macro-scale clinical applications possible, and the automatic process shows potential for development as an off-the-shelf immunotherapy product. This immunotherapy system could provide a clinical option for preventing tumor relapse and metastasis after tumor resection. Graphical Abstract Micro/macropore-forming hydrogel with NK cells fabricated by 3D bioprinting and implanted into the tumor site.

Injectable smart stimuli-responsive hydrogels: pioneering advancements in biomedical applications

“…53 Kim et al prepared an injectable biological ink consisting of gelatin and sodium alginate to 3D print micro/macropore-forming hydrogels. 138 They first 3D printed the hybrid hydrogel with macropores, and then crosslinked the hydrogel by 3% CaCl 2 . Thereafter, the hydrogel was incubated with natural killer (NK) cells under 37 °C, and interconnected micropores were generated as the gelatin was removed due to the its thermal sensitivity.…”

Advances in 3D bioprinting for regenerative medicine applications

“…However, the monitoring of the biological response of such multi-level co-culture structures can be quite taxing, especially the in vivo evaluation. Additionally, 3D bioprinting has showed great prospects as an alternative avenue for the delivery of immunogenicity-related molecules [ 46 , 294 ] and as tumor replicating platforms for drug screening applications [ 295–297 ]. Of particular interest is the bioprinting of immunomodulatory constructs encapsulating macrophages, as these cell types have shown to not only act as one of the chief regulators for immunogenic response, but also directly control chemotaxis-related processes of cell differentiation and tissue regrowth [ 279 , 298 , 299 ].…”

Harnessing the potential of hydrogels for advanced therapeutic applications: current achievements and future directions

“…delivered to localized tumor regions. 117 , 406 – 408

Fig. 7 a Schematic diagram of the installation process of the injectable delivery system.

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