Characterization of the sprayed platelet fibrin patch in vitro. (A) Mixing platelet-rich plasma with calcium-containing media solution in compressed air by the spray set resulted in a stable gel formation in less than 1 min; (B) Hematoxylin–eosin staining revealed a fibrous structure of the sprayed platelet fibrin gel; (C) Representative scanning electron microscopy images of the sprayed platelet fibrin gel; (D–H) Enzyme-linked immunosorbent assay (ELISA) of the concentrations of vascular endothelial growth factor (VEGF), insulin-like growth factor (IGF)-1, hepatocyte growth factor (HGF), platelet-derived growth factor (PDGF), and transforming growth factor-beta (TGF-β) from sprayed platelet fibrin gel conditioned media at different time points (n = 3 per time points). Scale bar = 100 μm. H & E, hematoxylin and eosin.