Biocompatibility Test. To study the biocompatibility of
the fibrous samples, MC3T3-E1 cells were used in our system,
which are commonly used to assess cytotoxicity of materials.
MC3T3-E1 cells were maintained at RPMI-l640 medium
with 10% fetal bovine serum and 1% antibiotic/antimycotic
solution in a 5% CO
2
incubator at 37
∘
C, refreshed every
3 days with Trypsin-EDTA solution, and then resuspended in a fresh culture medium. The PLA/PU and PLA/PU/GO
(5%) fibrous papers were cut into pieces (1 cm ×1cm) as
scaffolds, soaked in 75% ethanol for 1 h to be sterilized, and
then exchanged with PBS for three times (30min each).
The fibrous scaffolds were then washed with RPMI-1640
containing 10% FBS for two times (2 h each). 2×10
5
cell
suspension was seeded on each scaffold. The cell-scaffold
constructs were cultured in RPMI-l640 supplemented with
10% FBS, 1% antibiotic/antimycotic solution for up to 48h.
Finally, the cells were stained with acridine orange (AO),
which was cleaved to yield a green fluorescent product by
metabolically active cells.The density of the cells that adhered
on each scaffold was observed at 100-foldmagnification with
a fluorescence microscopy (Olympus BX51)