Extended Data Fig. 6: Development and characterization of bioprinting in the TRACE bath.
From: Instant assembly of collagen for tissue engineering and bioprinting
(a) The TRACE bath is prepared by combining agarose slurry and PEG solution in syringes connected via a 90° lure-lock connector. The agarose slurry is termed the “regular bath.” (b) Rheological characterization of shear moduli (G’: storage modulus; G”: loss modulus) of TRACE bath and regular bath as a function of shear strain at the oscillation frequency of 1 Hz. (c) Shear moduli of both baths as the function of shear frequency at the strain of 0.1%. (d) Viscosity characterization of collagen bioinks at various concentrations (2, 6, and 24 mg/mL) across various shear rate. All three inks exhibit shear-thinning behavior (N = 3 independently prepared inks per concentration; mean ± s.d.). (e) Assessing (top view) the structural integrity and shape retention of 2 mg/mL neutralized collagen blocks (L: 1 cm, W: 1 cm, H: 0.5 cm) with grid infill printed in TRACE, regular agarose slurry, and gelatin+HEPES support baths, after releasing in PBS. Scale bars, 5 mm. (f) Slicing and macroscopic photography of a collagen block (1 cm × 1 cm × 1 cm) with grid infill were printed using 6 mg/mL acetic collagen in the TRACE support bath. The construct is released in PBS. (g) A weight bearing test to assess structural integrity of bioprinted constructs using 6 mg/mL acetic collagen. Blocks (1 cm × 1 cm × 1 cm) with grid infill were printed in “Regular” or TRACE support baths, with an additional variant crosslinked with 10 mM genipin for 24 h post-released from TRACE bath. The sequence of images records structural integrity and deformation recovery for each construct before application of a 2.5 g weight, during the load, and after its removal. Scale bar, 5 mm. Collagen printed in the TRACE bath shows much higher resistance to compressive force. The unmodified collagen can be further reinforced by biocompatible crosslinkers, such as genipin.
