Polycaprolactone pcl

The BMS was fabricated with a 3DXP multi-head 3D bioprinter (TnR Biofab). The polycaprolactone (PCL, molecular weight = 70,000–90,000 g/mol, Polysciences) was used as a basement structure for the BMS. The PCL was printed for the middle and upper parts of BMS at 90 °C and 300 kPa. Then, the BM-ECM was printed on the middle part at 10 °C and 50 kPa, and was incubated at 37 °C for gelation. The printed BMS was vitrified for three days to completely dry out. After vitrification, the bottom part was printed using PCL.

The 3D printing inks were prepared using a solvent evaporation film casting method. Polycaprolactone (PCL, Mw 43–50 kDa, Polysciences, Warrington, PA), either alone or mixed with reduced graphene oxide (rGO, Sigma-Aldrich) at 0.5, 1 or 3 wt. % was dissolved in dichloromethane (DCM, Sigma Aldrich, St. Louis, MO). The weight of PCL or PCL + rGO to DCM was 1 g to 5 mL. The mixtures were vortexed at room temperature for 3 h to ensure the complete dissolution of PCL and the homogenous dispersion of rGO. The PCL or composite PCL-rGO films were prepared by casting the suspensions onto 100 mm glass petri dishes that were left to air-dry overnight. The films were subsequently collected and lyophilized for another 24 h. Lastly, the films were cut into smaller pellets for feeding into the cartridge of the 3D printer (Fig. 1).

To fabricate scaffolds, polycaprolactone (PCL; 43 kDa, Polysciences; Warrington, PA) was melted at 85°C and printed at a collector velocity of 40 mm s−1, 5.0 kV, 1.0 bar, at a distance of 10 mm using a 3DDiscovery Evolution printer, RegenHU, Switzerland, located in a laminar flow hood. Scaffolds, designed using computer-aided design software BioCAD (Regenhu, Switzerland), had a filament width of 35 μm and 90% porosity. They were stored in 70% ethanol until their application.
The scaffolds were implanted in parallel to the deep dermis/subcutis interface in mice within a dorsal skinfold chamber system, an optical imaging window that allows for in vivo inspection in real time (Figure 1B), as previously described (Dondossola et al., 2016 (link)). Longitudinal monitoring of the scaffolds started 4 days postimplantation and proceeded up to day 14.
For clodronate treatment experiments, mice implanted with the scaffold in the dorsal skinfold chamber received clodronate liposomes (1 mg/mouse, 200 μL, intravenously, following the manufacturers’ instructions, Liposoma) every two to three days, starting three days before scaffold implantation to deplete macrophages by the day of implantation, as reported (Dondossola et al., 2016 (link)).

The scaffold was fabricated by using fused deposition modeling (FDM) technology. Firstly, we put reagent grade polycaprolactone (PCL) (molecular weight = 43,000–50,000; Polysciences, Warrington, PA, USA) in the oven for one hour and set the temperature to 100 °C. The ratios of the GR/MSCS/PCL composite had divided into three groups, 0:50:50, 2:48:50, and 5:45:50; we named the codes as G0, G2, and G5, respectively. These composites were mixed in 99.5% alcohol and dripped gently into the melted PCL. The solution was then placed at 100 °C and stirred rapidly for 1 h to promote alcohol evaporation at room temperature. The 3D scaffold was fabricated by Bio-Scaffolder 3.1 (GeSiM, Grosserkmannsdorf, Radeberg, Germany) with a stable pressure of 330 kPa. All scaffolds were printed in parallel, with 400 μm struts, 300 μm height, and 500 μm spacing between each layer.