Mw 43 000

The protocols for the CS scaffold fabrication were adopted from our previous studies [33 (link)]. To obtain pure CS powder, CaO (99.9%, Sigma-Aldrich, St. Louis, MO, USA), SiO₂ (1 µm, 99.99%, Sigma-Aldrich), and Al₂O₃ (99.5%, Sigma-Aldrich) were added and mixed in proportions of 70%, 25%, and 5%, respectively, followed by sintering in a high-temperature furnace at 1400 °C for 2 h. Subsequently, varying amounts of Fe₃O₄ nanoparticles (100 nm, 97%, Sigma-Aldrich) were added to the CS powder (0, 2.5, and 5 wt. %) and ball-milled at 300 rpm for 12 h. The ball-milled product was then dried and mixed in a 1:1 ratio with poly-ε-caprolactone (PCL; Mw 43,000; Polysciences, Warrington, PA, USA). First, PCL was melted at 180 °C, then alcohol was added and uniformly stirred before being placed in an oven for 12 h of dehydration. The CS-PCL-Fe pastes were stored in a remodified storage until further use. Prior to printing, the pastes were placed into the printing cartridge with a 20G nozzle, heated to 80 °C, and printed at 2 mm/s and 240 kPa. The various groups were named according to the concentration of Fe₃O₄ used, namely Fe0, Fe2.5, and Fe5.

Cylindrical samples with a 5 mm diameter and 1 mm height were prepared through the biopsy punching of crosslinked DDMp bio-inks to measure the compressive modulus. After loading each sample into a universal testing machine (Instron Model 3342; Illinois Tool Works Inc., MA, USA), the sample was gradually compressed at a rate of 1 mm/min, and the corresponding force and distance were recorded. After plotting the strain–stress curve, the compressive modulus was measured by calculating a slope based on a 10% strain. In addition, a 3D hybrid construct of 5 × 5 × 5 mm³ produced through the co-printing of polycaprolactone (s; MW 43000; Polysciences Inc, Warrington, FL, USA) and DPSCs-laden DDMp bio-ink was measured for the compressive modulus identical to the DDMp bio-ink. The rheological property of the DDMp bio-inks was measured through shear sweep analysis, which was conducted at 0.1–100 s⁻¹ using a 20-mm-diameter plate at 18 °C on a HAAKE MARS III Rheometer (Thermo Scientific, Karlsruhe, Germany).