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. 2020 Jun 1;7:100058. doi: 10.1016/j.mtbio.2020.100058

Fig. 2.

Fig. 2

Collagen (Col 1) fibril distribution in THA hydrogel and rheological properties. (A) Visualization of Col 1 fibrils within Col 1 hydrogel and (B) THA-Col 1 hydrogels using confocal imaging (immunofluorescent staining for Col 1) and (C–D) SHG imaging (no labeling), respectively. Both techniques illustrate homogenous distribution of Col 1 fibrils (scale bar = 100 μm). (E) Turbidity measurement of THA-Col 1 demonstrated Col 1 fibril formation in the composite dependent on Col 1 content. The more the presence of Col 1 in the composite, the higher the absorbance at 313 nm over time, with maximum values for Col 1 only. (F) Viscosity curve (as function of the shear rate) demonstrates shear thinning behavior of THA, THA-Col 1, and neutralized Col 1, marked by decreasing viscosity with increasing shear rate. Col 1 (pH 7, 5 mg/ml) showed lower viscosity than THA (25 mg/ml) and THA-Col 1. Acidic Col 1(pH 4, 5 mg/ml) lacks shear thinning behavior with a constant viscosity over a range of tested shear rates. (G) Rheological characterization (amplitude sweep, 1 Hz) to evaluate mechanical properties of biomaterial ink by means of storage (G') and loss (G'`) modulus of THA-Col 1 and THA after enzymatic cross-linking. Storage modulus increases in the composite compared with THA. THA = tyramine derivative of hyaluronan; SHG = second-harmonic generation; Col 1 = collagen type I hydrogel.