Fisherbrand model 50 sonic dismembrator

A set of 3D scaffolds were fabricated using a 3D Bioplotter (EnvisionTEC, Gladbeck, NRW, Germany). Briefly, 2.1 g of ground PLGA was mixed with 0.9 g of nHA and 3.6 mL of HFP in a 25 mL beaker for 120 s. In addition, 0.225 g of collagen and 3 mL of HFP were mixed for 90 s in another 25 mL beaker. Both beakers were then sealed and kept under a fume hood for 23 h. Then, 0.42 g of ground PEG (20% of PLGA mass) was added to the PLGA-nHA beaker. Finally, the collagen solution was poured into the beaker, and the solution was mixed for 5 min, followed by sonication at an amplitude of 40 μm for 3 min with a Fisherbrand Model 50 Sonic Dismembrator (Fisher Scientific, Portsmouth, NH, USA). The 3D Bioplotter was calibrated prior to scaffold fabrication. The 3D geometry used for 3D plotting was a 20 mm × 20 mm × 3 mm block partitioned into 300 μm layers, which enabled some overlap between the successive layers to prevent delamination [20 (link)]. The 3D Bioplotter was set to a pressure of 1.5 bar, a dispensing speed of 2.4 mm/s, and a temperature of 20 °C. The edge-to-edge distance between the plotted strands was set to 1000 μm. The scaffolds were dried under the fume hood for 14 days. The plasma-treated scaffold samples used for the BCA assay were immersed in PBS immediately after the plasma treatment.