Fig. 1. Schematic illustration and characterization of bead-jet printing.

a High-throughput intra-operative formulation and printing of MSCs-laden Matrigel beads. b Parallel comparison of printed high cell density beads (HDB) and low cell density beads (LDB), or cast high cell density bulk gel (HDG). The empty space was printed with acellular beads or cast with acellular bulk gel. c Bead-jet printing augments stem cell retention, reduces stem cell consumption, and increases volumetric injury recovery in muscle and skin regeneration. d Homogenous structures of printed gelatin beads, including a THU alphabetical sparse pattern, and rectangular, triangular, and hexagonal dense patterns. Scale bar, 5 mm. e Heterogeneous structures of printed gelatin beads of two different colors. Scale bar, 5 mm. f Mono-layer printed gelatin beads preserved the bead-to-bead interface and formed bead bonds on a sacrificial gelatin support. g Printing precision evaluation by measuring the deposition deviation at ejection distances of 5, 8, 12 mm. n = 50 for each measurement. Data are represented as mean ± SD. h Viability ratios of MSCs in gelatin beads, measured before printing (positive control), after printing straight into the DMEM medium, and after printing first on sacrificial gelatin support followed by transferring to the DMEM medium. The viability rates were measured after 3 days in culture. n = 3 for each measurement. Data are represented as mean ± SD (standard deviation), **P < 0.01. The significant difference is determined by one-way ANOVA, followed by Tukey’s test. i 3D Printing of multi-layer gelatin beads on sacrificial gelatin support. The printed assembly had 15 layers. Scale bar, 1 cm. j Advancing angle measurement of 3D printed bead assemblies with increasing layers. n = 3 for each measurement. Data are represented as mean ± SD.