Complex patient-specific bone defects remain difficult to reconstruct because the regenerative capacity of bone is limited and prefabricated implants cannot readily match defect geometry. In this work, methylcellulose-gelatin-hydroxyapatite (MC/GEL/HA) inks were formulated with varying methylcellulose content and hydroxyapatite incorporation, crosslinked with EDC/NHS, and 3D-printed into porous scaffolds with defined square-pore architectures. Inks were evaluated by oscillatory and steady-shear rheology, and printed scaffolds were characterized for morphology, chemical composition, mechanical performance, physicochemical stability, wettability, apatite-forming bioactivity, and osteogenic responses of human bone marrow mesenchymal stem cells. Methylcellulose content primarily governed ink rheology and printability, and increased compressive strength (up to ~0.38 MPa for 15MC/10GEL/30HA), whereas hydroxyapatite enhanced surface hydrophilicity, promoted apatite nucleation within 7 days in simulated body fluid, and markedly increased alkaline phosphatase activity (>10-fold over HA-free scaffolds), mineralization (~2-fold by Alizarin Red), and the highest osteocalcin expression among the HA-containing formulations (~2.45-fold at day 14). The 15MC/10GEL/30HA formulation showed the most favorable balance of printability, mechanical performance, and osteogenic performance. These complementary functions reconciled structural stability with osteogenic performance, supporting the MC/GEL/HA system as a tunable bioink platform for non-weight-bearing bone regeneration, while warranting further in vivo validation.

In the innate immune system, natural killer (NK) cells are effector lymphocytes which control several tumor types and microbial infections by limiting disease spread and tissue damage. With tumor cell killing abilities, with no priming or prior activation, NKs are potential anti-cancer therapies. In clinical practice, NKs are used in intravenous injections as they typically grow as suspension, similar to other blood cells. In this study, we designed a novel and effective biomaterial-based platform for NK cell delivery, which included in situ NK cell encapsulation into three-dimensional (3D) biocompatible polymeric scaffolds for potential anti-cancer treatments. Depending on physical cross-linking between an alginate (ALG) polymer and a divalent cation, two natural polymers (gelatin (GEL) and hyaluronic acid (HA)) penetrated into pores and generated an inter-penetrating hydrogel system with improved mechanical properties and stability. After extensive characterization of hydrogels, NK cells were encapsulated inside using our in situ gelation procedure to provide a biomimetic microenvironment.