Fig. 1.

Schematic illustration of GEL-dbPTs composite scaffolds. (A) GEL and (B) dbPTs were used for the preparation of the composite scaffolds. (i) General morphology (left, scale bar: 100 ​μm) of the dbPTs composed of collagen fibers (middle, scale bar: 1 ​μm) and hydroxyapatite crystals (right, scale bar: 1 ​μm) shown in the SEM images. (ii) Energy dispersive x-ray spectrum of the dbPTs indicating the carbon (C), oxygen (O), magnesium (Mg), phosphorus (P), sodium (Na), and calcium (Ca) contents. Scale bars: 500 ​μm. (C) To obtain the biomaterial ink, GEL and dbPTs were mixed, then (D) the GEL/dbPT ink was printed using a 3D extrusion printer. Subsequently, printed scaffolds were cross-linked with mTG by forming the isopeptide bond via lysine and glutamine amino groups. Thus, 3D printed GEL/dbPTs composite scaffolds were produced, and the physicochemical, mechanical properties as well as the cytocompatibility, and cell-material interaction were investigated.