Creation and functionalization of 3D titanium–spongin composites

Naturally pre-structured three-dimensional (3D) scaffolds derived from commercial marine sponges represent renewable biomaterials with hierarchical, porous architecture optimized by evolution. For the first time, purified spongin scaffolds from Hippospongia communis sponges were functionalized via ion–plasma vacuum arc deposition of titanium, followed by high-temperature carbonization. The applied metallization process preserved the native open-cell 3D architecture of spongin while introducing an α-Ti nanostructured surface layer. Subsequent carbonization at 1200 °C led to the formation of turbostratic carbon and crystalline titanium carbide/oxycarbide phases, as confirmed by SEM, EDX, HRTEM, XRD, and Raman spectroscopy. The biological response of MG-63 osteoblast-like cells was evaluated using indirect cytocompatibility screening, Live/Dead confocal microscopy, WST-1 metabolic activity analysis, protein-normalized ALP-associated activity, and immunofluorescence staining of osteoblast- and adhesion-associated markers. MG-63 cells were selected to provide a bone-relevant osteoblast-like in vitro model for assessing cell–material interactions on Ti-containing spongin-based scaffolds. Ti–Spg and C–Ti–Spg scaffolds demonstrated enhanced cell coverage after 7 days of culture compared with native spongin. At day 14, C–Ti–Spg showed the highest protein-normalized ALP-associated activity together with the most extensive RUNX2-, OPN- and FAK-associated immunostaining pattern, supporting enhanced osteoblast-related activity and adhesion/matrix-associated cell–scaffold interactions under basal culture conditions. Complementary WST-1 metabolic readouts and FDA/PI confocal imaging did not indicate material-induced cytotoxicity, while WST-1 data were interpreted as relative metabolic indicators because colorimetric assays in 3D porous scaffolds can be influenced by reagent diffusion and scaffold architecture. This study demonstrates that naturally prefabricated 3D spongin scaffolds can be successfully metallized with Ti and converted into TiC-containing carbonized composites without loss of structural integrity or cytocompatibility. The combination of preserved hierarchical architecture with titanium-based surface chemistry provides a sustainable platform for the further development of bioinspired functional scaffolds for tissue engineering applications.