Carboxymethyl cellulose

Nitrocellulose (NC, A grade) was provided by North Sichuan Nitrocellulose Co., China. 2,2-Azobisisobutyronitrile (AIBN, 98.5%), 3-(trimethoxysilyl) propylmethacrylate (MPS, 97%), ethanol (99.7%), acetic acid (99.5%) and deionized water were purchased from Nanjing Chemical Reagent Co., Nanjing, China. Methylacrylic acid (MAA, 98%), tetraethoxysilicane (TEOS), acetone (99.7%) and methanol (99.5%) were obtained from Sinopharm Chemical Reagent Co., Nanjing, China. Ammonium hydroxide was provided by Shanghai Lingfeng Chemical Reagent Co., China. Ethylene glycol dimethacrylate (EGDMA, 98%) was purchased from Aladdin Reagent Co., Shanghai, China. Methyl cellulose (MC, 15 mPa s) was purchased from Meryer Chemical Technology Co., Shanghai, China. Carboxymethyl cellulose (CMC, 600–1000 mPa s, USP grade) and hydroxypropyl cellulose (HPC, M. W.100 000) were purchased from Macklin Biochemical Co., Shanghai, China. AIBN was recrystallized from ethanol before use, and all other chemicals were used directly without purification.

1.1 g poly(lactide-co-glycolic acid) (PLGA, 85 : 15 lactide: glycolide, M_w = 400 kDa) was dissolved in 20 mL dichloromethane (DCM, Taitan, China) by magnetic stirring for 2 h at 20 °C. Then a commercial airbrush (HD-150, Syou Tools, China) was use to airbrush the solution (2 MPa air pression, 0.5 mm-diameter nozzle). The distance from receiver (wrapped in aluminum foil) to nozzle of airbrush was 30 cm. Then the collected fibers were placed in a vacuum drying oven at 40 °C to remove the solvent for 24 h. Next, they were embrittled with liquid nitrogen for 5 min and crushed with mortar immediately. Finally, the short nanofibers (Fig. S1) were sieved out with screens. Calcium phosphate cement powder (Rebone, China) was composed of equimolar tetracalcium phosphate (TTCP, Ca₄(PO₄)₂O) and dicalcium phosphate anhydrous (DCPA, CaHPO₄). CPC, PLGA nanofibers and carboxymethyl cellulose (CMC, Macklin, China) were mixed and stirred in a small beaker, meanwhile, the mixture was ultrasound for 5 min. Then pastes were fabricated by mixing the solid-phase composite and 4 wt% NaH₂PO₄·H₂O (Yonghua, China), at a 2 : 1 powder-liquid ratio. The composition of cements was listed in Table S1.

Carboxymethyl cellulose with average molecular weight of 700 000 (DS = 0.9) and viscosity of 2500–4500 mPa s was purchased from Shanghai Macklin Biochemical Technology Co., Ltd. The CMC was used as received without further purification or treatment. Single layed graphene powder was purchased from Kaisa New Materials Co. Ltd. Conductive tape with thickness of 1 mm and width of 5 mm was purchased from Shenzhen Changdasheng electronics Co., Ltd. The ultra-pure water used in this study was made by the ultrapure water machine (WP-RO-10B, Water Purifier).